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; Implementation of periodic transaction scheduler for USB.

; Bandwidth dedicated to periodic transactions is limited, so

; different pipes should be scheduled as uniformly as possible.

; USB2 scheduler.

; There are two parts: high-speed pipes and split-transaction pipes.

;

; High-speed scheduler uses the same algorithm as USB1 scheduler:

; when adding a pipe, optimize the following quantity:

;  * for every microframe, take all bandwidth scheduled to periodic transfers,

;  * calculate maximum over all microframes,

;  * select a variant which minimizes that maximum;

;  * if there are several such variants,

;    prefer those that are closer to end of frame

;    to minimize collisions with split transactions;

; when removing a pipe, do nothing (except for bookkeeping).

; in: esi -> usb_controller

; out: edx -> usb_static_ep, eax = S-Mask

proc ehci_select_hs_interrupt_list

; inherit some variables from usb_open_pipe

virtual at ebp-12

.targetsmask    dd      ?

.bandwidth      dd      ?

.target         dd      ?

                dd      ?

                dd      ?

.config_pipe    dd      ?

.endpoint       dd      ?

.maxpacket      dd      ?

.type           dd      ?

.interval       dd      ?

end virtual

; prolog, initialize local vars

        or      [.bandwidth], -1

        or      [.target], -1

        or      [.targetsmask], -1

        push    ebx edi         ; save used registers to be stdcall

; 1. In EHCI, every list describes one millisecond = 8 microframes.

; Thus, there are two significantly different branches:

; for pipes with interval >= 8 microframes, advance to 2,

; for pipes which should be planned in every frame (one or more microframes),

; go to 9.

; Note: the actual interval for high-speed devices is 2^([.interval]-1),

; (the core specification forbids [.interval] == 0)

        mov     ecx, [.interval]

        dec     ecx

        cmp     ecx, 3

        jb      .every_frame

; 2. Determine the actual interval in milliseconds.

        sub     ecx, 3

        cmp     ecx, 5  ; maximum 32ms

        jbe     @f

        movi    ecx, 5

@@:

; There are four nested loops,

; * Loop #4 (the innermost one) calculates the total periodic bandwidth

;   scheduled in the given microframe of the given millisecond.

; * Loop #3 calculates the maximum over all milliseconds

;   in the given variant, that is the quantity we're trying to minimize.

; * Loops #1 and #2 check all variants;

;   loop #1 is responsible for the target millisecond,

;   loop #2 is responsible for the microframe within millisecond.

; 3. Prepare for loops.

; ebx = number of iterations of loop #1

; [esp] = delta of counter for loop #3, in bytes

; [esp+4] = delta between the first group and the target group, in bytes

        movi    ebx, 1

        movi    edx, sizeof.ehci_static_ep

        shl     ebx, cl

        shl     edx, cl

        mov     eax, 64*sizeof.ehci_static_ep

        sub     eax, edx

        sub     eax, edx

        push    eax

        push    edx

; 4. Select the best variant.

; 4a. Loop #1: initialize counter = pointer to ehci_static_ep for

; the target millisecond in the first group.

        lea     edx, [esi+ehci_controller.IntEDs-sizeof.ehci_controller]

.varloop0:

; 4b. Loop #2: initialize counter = microframe within the target millisecond.

        xor     ecx, ecx

.varloop:

; 4c. Loop #3: save counter of loop #1,

; initialize counter with the value of loop #1 counter,

; initialize maximal bandwidth = zero.

        xor     edi, edi

        push    edx

virtual at esp

.saved_counter1         dd      ?       ; step 4c

.loop3_delta            dd      ?       ; step 3

.target_delta           dd      ?       ; step 3

end virtual

.calc_max_bandwidth:

; 4d. Loop #4: initialize counter with the value of loop #3 counter,

; initialize total bandwidth = zero.

        xor     eax, eax

        push    edx

.calc_bandwidth:

; 4e. Loop #4: add the bandwidth from the current list

; and advance to the next list, while there is one.

        add     ax, [edx+ehci_static_ep.Bandwidths+ecx*2]

        mov     edx, [edx+ehci_static_ep.NextList]

        test    edx, edx

        jnz     .calc_bandwidth

; 4f. Loop #4 end: restore counter of loop #3.

        pop     edx

; 4g. Loop #3: update maximal bandwidth.

        cmp     eax, edi

        jb      @f

        mov     edi, eax

@@:

; 4h. Loop #3: advance the counter and repeat while within the first group.

        lea     eax, [esi+ehci_controller.IntEDs+32*sizeof.ehci_static_ep-sizeof.ehci_controller]

        add     edx, [.loop3_delta]

        cmp     edx, eax

        jb      .calc_max_bandwidth

; 4i. Loop #3 end: restore counter of loop #1.

        pop     edx

; 4j. Loop #2: if the current variant is better (maybe not strictly)

; then the previous optimum, update the optimal bandwidth and the target.

        cmp     edi, [.bandwidth]

        ja      @f

        jb      .update

        cmp     ecx, [.targetsmask]

        jb      @f

.update:

        mov     [.bandwidth], edi

        mov     [.target], edx

        mov     [.targetsmask], ecx

@@:

; 4k. Loop #2: continue 8 times for every microframe.

        inc     ecx

        cmp     ecx, 8

        jb      .varloop

; 4l. Loop #1: advance counter and repeat ebx times,

; ebx was calculated in step 3.

        add     edx, sizeof.ehci_static_ep

        dec     ebx

        jnz     .varloop0

; 5. Calculate bandwidth for the new pipe.

        mov     eax, [.maxpacket]

        call    calc_hs_bandwidth

        mov     ecx, [.maxpacket]

        shr     ecx, 11

        inc     ecx

        and     ecx, 3

        imul    eax, ecx

; 6. Get the pointer to the best list.

        pop     edx             ; restore value from step 3

        pop     edx             ; get delta calculated in step 3

        add     edx, [.target]

; 7. Check that bandwidth for the new pipe plus old bandwidth

; still fits to maximum allowed by the core specification

; current [.bandwidth] + new bandwidth <= limit;

; USB2 specification allows maximum 60000*80% bit times for periodic microframe

        mov     ecx, [.bandwidth]

        add     ecx, eax

        cmp     ecx, 48000

        ja      .no_bandwidth

; 8. Convert {o|u}hci_static_ep to usb_static_ep, update bandwidth and return.

        mov     ecx, [.targetsmask]

        add     [edx+ehci_static_ep.Bandwidths+ecx*2], ax

        add     edx, ehci_static_ep.SoftwarePart

        movi    eax, 1

        shl     eax, cl

        pop     edi ebx         ; restore used registers to be stdcall

        ret

.no_bandwidth:

        dbgstr 'Periodic bandwidth limit reached'

        xor     eax, eax

        xor     edx, edx

        pop     edi ebx

        ret

.every_frame:

; The pipe should be scheduled every frame in two or more microframes.

; 9. Calculate maximal bandwidth for every microframe: three nested loops.

; 9a. The outermost loop: ebx = microframe to calculate.

        xor     ebx, ebx

.calc_all_bandwidths:

; 9b. The intermediate loop:

; edx = pointer to ehci_static_ep in the first group, [esp] = counter,

; edi = maximal bandwidth

        lea     edx, [esi+ehci_controller.IntEDs-sizeof.ehci_controller]

        xor     edi, edi

        push    32

.calc_max_bandwidth2:

; 9c. The innermost loop: calculate bandwidth for the given microframe

; in the given frame.

        xor     eax, eax

        push    edx

.calc_bandwidth2:

        add     ax, [edx+ehci_static_ep.Bandwidths+ebx*2]

        mov     edx, [edx+ehci_static_ep.NextList]

        test    edx, edx

        jnz     .calc_bandwidth2

        pop     edx

; 9d. The intermediate loop continued: update maximal bandwidth.

        cmp     eax, edi

        jb      @f

        mov     edi, eax

@@:

        add     edx, sizeof.ehci_static_ep

        dec     dword [esp]

        jnz     .calc_max_bandwidth2

        pop     eax

; 9e. Push the calculated maximal bandwidth and continue the outermost loop.

        push    edi

        inc     ebx

        cmp     ebx, 8

        jb      .calc_all_bandwidths

virtual at esp

.bandwidth7     dd      ?

.bandwidth6     dd      ?

.bandwidth5     dd      ?

.bandwidth4     dd      ?

.bandwidth3     dd      ?

.bandwidth2     dd      ?

.bandwidth1     dd      ?

.bandwidth0     dd      ?

end virtual

; 10. Select the best variant.

; edx = S-Mask = bitmask of scheduled microframes

        movi    edx, 0x11

        cmp     ecx, 1

        ja      @f

        mov     dl, 0x55

        jz      @f

        mov     dl, 0xFF

@@:

; try all variants edx, edx shl 1, edx shl 2, ...

; while they fit in the lower byte (8 microframes per frame)

.select_best_mframe:

        xor     edi, edi

        mov     ecx, edx

        mov     eax, esp

.calc_mframe:

        add     cl, cl

        jnc     @f

        cmp     edi, [eax]

        jae     @f

        mov     edi, [eax]

@@:

        add     eax, 4

        test    cl, cl

        jnz     .calc_mframe

        cmp     [.bandwidth], edi

        jb      @f

        mov     [.bandwidth], edi

        mov     [.targetsmask], edx

@@:

        add     dl, dl

        jnc     .select_best_mframe

; 11. Restore stack after step 9.

        add     esp, 8*4

; 12. Get the pointer to the target list (responsible for every microframe).

        lea     edx, [esi+ehci_controller.IntEDs.SoftwarePart+62*sizeof.ehci_static_ep-sizeof.ehci_controller]

; 13. Calculate bandwidth on the bus.

        mov     eax, [.maxpacket]

        call    calc_hs_bandwidth

        mov     ecx, [.maxpacket]

        shr     ecx, 11

        inc     ecx

        and     ecx, 3

        imul    eax, ecx

; 14. Check that current [.bandwidth] + new bandwidth <= limit;

; USB2 specification allows maximum 60000*80% bit times for periodic microframe.

        mov     ecx, [.bandwidth]

        add     ecx, eax

        cmp     ecx, 48000

        ja      .no_bandwidth

; 15. Update bandwidths including the new pipe.

        mov     ecx, [.targetsmask]

        lea     edi, [edx+ehci_static_ep.Bandwidths-ehci_static_ep.SoftwarePart]

.update_bandwidths:

        shr     ecx, 1

        jnc     @f

        add     [edi], ax

@@:

        add     edi, 2

        test    ecx, ecx

        jnz     .update_bandwidths

; 16. Return target list and target S-Mask.

        mov     eax, [.targetsmask]

        pop     edi ebx         ; restore used registers to be stdcall

        ret

endp

; Pipe is removing, update the corresponding lists.

; We do not reorder anything, so just update book-keeping variable

; in the list header.

proc ehci_hs_interrupt_list_unlink

        movzx   eax, word [ebx+ehci_pipe.Token-sizeof.ehci_pipe+2]

; calculate bandwidth

        call    calc_hs_bandwidth

        mov     ecx, [ebx+ehci_pipe.Flags-sizeof.ehci_pipe]

        shr     ecx, 30

        imul    eax, ecx

        movzx   ecx, byte [ebx+ehci_pipe.Flags-sizeof.ehci_pipe]

; get target list

        mov     edx, [ebx+usb_pipe.BaseList]

; update bandwidth

.dec_bandwidth:

        shr     ecx, 1

        jnc     @f

        sub     word [edx+ehci_static_ep.Bandwidths - ehci_static_ep.SoftwarePart], ax

@@:

        add     edx, 2

        test    ecx, ecx

        jnz     .dec_bandwidth

; return

        ret

endp

; Helper procedure for USB2 scheduler: calculate bandwidth on the bus.

; in: low 11 bits of eax = payload size in bytes

; out: eax = maximal bandwidth in HS-bits

proc calc_hs_bandwidth

        and     eax, (1 shl 11) - 1     ; get payload for one transaction

        add     eax, 3  ; add 3 bytes for other fields in data packet, PID+CRC16

; Multiply by 8 for bytes -> bits and then by 7/6 to accomodate bit stuffing;

; total 28/3 = 9+1/3

        mov     edx, 55555556h

        lea     ecx, [eax*9]

        mul     edx

; Add 989 extra bits: 68 bits for Token packet (32 for SYNC, 24 for token+address,

; 4 extra bits for possible bit stuffing in token+address, 8 for EOP),

; 736 bits for bus turn-around, 40 bits for SYNC+EOP in Data packet,

; 8 bits for inter-packet delay, 49 bits for Handshake packet,

; 88 bits for another inter-packet delay.

        lea     eax, [ecx+edx+989]

        ret

endp

; Split-transaction scheduler (aka TT scheduler, TT stands for Transaction

; Translator, section 11.14 of the core spec) needs to schedule three event

; types on two buses: Start-Split and Complete-Split on HS bus and normal

; transaction on FS/LS bus.

; Assume that FS/LS bus is more restricted and more important to be scheduled

; uniformly, so select the variant which minimizes maximal used bandwidth

; on FS/LS bus and does not overflow HS bus.

; If there are several such variants, prefer variants which is closest to

; start of frame, and within the same microframe consider HS bandwidth

; utilization as a last criteria.

; The procedure ehci_select_tt_interrupt_list has been splitted into several

; macro, each representing a logical step of the procedure,

; to simplify understanding what is going on. Consider all the following macro

; as logical parts of one procedure, they are meaningless outside the context.

; Given a frame, calculate bandwidth occupied by already opened pipes

; in every microframe.

; Look for both HS and FS/LS buses: there are 16 words of information,

; 8 for HS bus, 8 for FS/LS bus, for every microframe.

; Since we count already opened pipes, the total bandwidth in every microframe

; is less than 60000 bits (and even 60000*80% bits), otherwise the scheduler

; would not allow to open those pipes.

; edi -> first list for the frame

macro tt_calc_bandwidth_in_frame

{

local .lists, .pipes, .pipes_done, .carry

; 1. Zero everything.

        xor     eax, eax

        mov     edx, edi

repeat 4

        mov     dword [.budget+(%-1)*4], eax

end repeat

repeat 4

        mov     dword [.hs_bandwidth+(%-1)*4], eax

end repeat

        mov     [.total_budget], ax

; Loop over all lists for the given frame.

.lists:

; 2. Total HS bandwidth for all pipes in one list is kept inside list header,

; add it. Note that overflow is impossible, so we may add entire dwords.

        mov     ebx, [edx+ehci_static_ep.SoftwarePart+usb_static_ep.NextVirt]

repeat 4

        mov     eax, dword [edx+ehci_static_ep.Bandwidths+(%-1)*4]

        add     dword [.hs_bandwidth+(%-1)*4], eax

end repeat

; Loop over all pipes in the given list.

        add     edx, ehci_static_ep.SoftwarePart

.pipes:

        cmp     ebx, edx

        jz      .pipes_done

; 3. For every pipe in every list for the given frame:

; 3a. Check whether the pipe resides on the same FS/LS bus as the new pipe.

; If not, skip this pipe.

        mov     eax, [ebx+usb_pipe.DeviceData]

        mov     eax, [eax+usb_device_data.TTHub]

        cmp     eax, [.tthub]

        jnz     @f

; 3b. Calculate FS/LS budget for the opened pipe.

; Note that eax = TTHub after 3a.

        call    tt_calc_budget

; 3c. Update total budget: add the value from 3b

; to the budget of the first microframe scheduled for this pipe.

        bsf     ecx, [ebx+ehci_pipe.Flags-sizeof.ehci_pipe]

        add     [.budget+ecx*2], ax

@@:

        mov     ebx, [ebx+usb_pipe.NextVirt]

        jmp     .pipes

.pipes_done:

        mov     edx, [edx+ehci_static_ep.NextList-ehci_static_ep.SoftwarePart]

        test    edx, edx

        jnz     .lists

; 4. If the budget for some microframe is exceeded, carry it to the following

; microframe(s). The actual size of one microframe is 187.5 raw bytes;

; the core spec says that 188 bytes should be scheduled in every microframe.

        xor     eax, eax

        xor     ecx, ecx

.carry:

        xor     edx, edx

        add     ax, [.budget+ecx*2]

        cmp     ax, 188

        jbe     @f

        mov     dx, ax

        mov     ax, 188

        sub     dx, ax

@@:

        mov     [.budget+ecx*2], ax

        add     [.total_budget], ax

        mov     ax, dx

        inc     ecx

        cmp     ecx, 8

        jb      .carry

}

; Checks whether the new pipe fits in the existing FS budget

; starting from the given microframe. If not, mark the microframe

; as impossible for scheduling.

; in: ecx = microframe

macro tt_exclude_microframe_if_no_budget

{

local .loop, .good, .bad

; 1. If the new budget plus the current budget does not exceed 188 bytes,

; the variant is possible.

        mov     ax, [.budget+ecx*2]

        mov     edx, ecx

        add     ax, [.new_budget]

        sub     ax, 188

        jbe     .good

; 2. Otherwise,

; a) nothing should be scheduled in some following microframes,

; b) after adding the new budget everything should fit in first 6 microframes,

;    this guarantees that even in the worst case 90% limit is satisfied.

.loop:

        cmp     edx, 5

        jae     .bad

        cmp     [.budget+(edx+1)*2], 0

        jnz     .bad

        inc     edx

        sub     ax, 188

        ja      .loop

.bad:

        btr     [.possible_microframes], ecx

.good:

}

; Calculate data corresponding to the particular scheduling variant for the new pipe.

; Data describe the current scheduling state collected over all frames touched

; by the given variant: maximal HS bandwidth, maximal FS/LS budget,

; which microframes fit in the current FS/LS budget for all frames.

macro tt_calc_statistics_for_one_variant

{

local .frames, .microframes

; 1. Initialize: zero maximal bandwidth,

; first 6 microframes are possible for scheduling.

        xor     eax, eax

repeat 4

        mov     dword [.max_hs_bandwidth+(%-1)*4], eax

end repeat

        mov     [.max_fs_bandwidth], ax

        mov     [.possible_microframes], 0x3F

; Loop over all frames starting with [.variant] advancing by [.variant_delta].

        mov     edi, [.variant]

.frames:

; 2. Calculate statistics for one frame.

        tt_calc_bandwidth_in_frame

; 3. Update maximal FS budget.

        mov     ax, [.total_budget]

        cmp     ax, [.max_fs_bandwidth]

        jb      @f

        mov     [.max_fs_bandwidth], ax

@@:

; 4. For every microframe, update maximal HS bandwidth

; and check whether the microframe is allowed for scheduling.

        xor     ecx, ecx

.microframes:

        mov     ax, [.hs_bandwidth+ecx*2]

        cmp     ax, [.max_hs_bandwidth+ecx*2]

        jb      @f

        mov     [.max_hs_bandwidth+ecx*2], ax

@@:

        tt_exclude_microframe_if_no_budget

        inc     ecx

        cmp     ecx, 8

        jb      .microframes

; Stop loop when outside of first descriptor group.

        lea     eax, [esi+ehci_controller.IntEDs+32*sizeof.ehci_static_ep-sizeof.ehci_controller]

        add     edi, [.variant_delta]

        cmp     edi, eax

        jb      .frames

}

struct usb_split_info

microframe_mask         dd      ?       ; lower byte is S-mask, second byte is C-mask

ssplit_bandwidth        dd      ?

csplit_bandwidth        dd      ?

ends

; Check whether the current variant and the current microframe are allowed

; for scheduling. If so, check whether they are better than the previously

; selected variant+microframe, if any. If so, update the previously selected

; variant+microframe to current ones.

; ecx = microframe, [.variant] = variant

macro tt_check_variant_microframe

{

local .nothing, .update, .ssplit, .csplit, .csplit_done

; 1. If the current microframe does not fit in existing FS budget, do nothing.

        bt      [.possible_microframes], ecx

        jnc     .nothing

; 2. Calculate maximal HS bandwidth over all affected microframes.

; 2a. Start-split phase: one or more microframes starting with ecx,

; coded in lower byte of .info.microframe_mask.

        xor     ebx, ebx

        xor     edx, edx

.ssplit:

        lea     eax, [ecx+edx]

        movzx   eax, [.max_hs_bandwidth+eax*2]

        add     eax, [.info.ssplit_bandwidth]

        cmp     ebx, eax

        ja      @f

        mov     ebx, eax

@@:

        inc     edx

        bt      [.info.microframe_mask], edx

        jc      .ssplit

; 2b. Complete-split phase: zero or more microframes starting with

; ecx+(last start-split microframe)+2,

; coded in second byte of .info.microframe_mask.

        add     edx, 8

.csplit:

        inc     edx

        bt      [.info.microframe_mask], edx

        jnc     .csplit_done

        lea     eax, [ecx+edx]

        cmp     eax, 8

        jae     .csplit_done

        movzx   eax, [.max_hs_bandwidth+(eax-8)*2]

        add     eax, [.info.csplit_bandwidth]

        cmp     ebx, eax

        ja      .csplit

        mov     ebx, eax

        jmp     .csplit

.csplit_done:

; 3. Check that current HS bandwidth + new bandwidth <= limit;

; USB2 specification allows maximum 60000*80% bit times for periodic microframe.

        cmp     ebx, 48000

        ja      .nothing

; 4. This variant is possible for scheduling.

; Check whether it is better than the currently selected one.

; 4a. The primary criteria: FS/LS bandwidth.

        mov     ax, [.max_fs_bandwidth]

        cmp     ax, [.best_fs_bandwidth]

        ja      .nothing

        jb      .update

; 4b. The secondary criteria: prefer microframes which are closer to start of frame.

        cmp     ecx, [.targetsmask]

        ja      .nothing

        jb      .update

; 4c. The last criteria: HS bandwidth.

        cmp     ebx, [.bandwidth]

        ja      .nothing

.update:

; 5. This variant is better than the previously selected.

; Update the best variant with current data.

        mov     [.best_fs_bandwidth], ax

        mov     [.bandwidth], ebx

        mov     [.targetsmask], ecx

        mov     eax, [.variant]

        mov     [.target], eax

.nothing:

}

; TT scheduler: add new pipe.

; in: esi -> usb_controller, edi -> usb_pipe

; out: edx -> usb_static_ep, eax = S-Mask

proc ehci_select_tt_interrupt_list

virtual at ebp-12-.local_vars_size

.local_vars_start:

.info                   usb_split_info

.new_budget             dw      ?

.total_budget           dw      ?

.possible_microframes   dd      ?

.tthub                  dd      ?

.budget                 rw      8

.hs_bandwidth           rw      8

.max_hs_bandwidth       rw      8

.max_fs_bandwidth       dw      ?

.best_fs_bandwidth      dw      ?

.variant                dd      ?

.variant_delta          dd      ?

.target_delta           dd      ?

.local_vars_size = $ - .local_vars_start

if .local_vars_size > 24*4

err Modify stack frame size in

end if

.targetsmask    dd      ?

.bandwidth      dd      ?

.target         dd      ?

                dd      ?

                dd      ?

.config_pipe    dd      ?

.endpoint       dd      ?

.maxpacket      dd      ?

.type           dd      ?

.interval       dd      ?

end virtual

        mov     eax, [edi+ehci_pipe.Token-sizeof.ehci_pipe]

        shr     eax, 16

        and     eax, (1 shl 11) - 1

        push    ebx edi

; 1. Compute the real interval. FS/LS devices encode the interval as

; number of milliseconds. Use the maximal power of two that is not greater than

; the given interval and EHCI scheduling area = 32 frames.

        cmp     [.interval], 1

        adc     [.interval], 0

        mov     ecx, 64

        mov     eax, 64 * sizeof.ehci_static_ep

@@:

        shr     ecx, 1

        cmp     [.interval], ecx

        jb      @b

        mov     [.interval], ecx

; 2. Compute variables for further calculations.

; 2a. [.variant_delta] is delta between two lists from the first group

; that correspond to the same variant.

        imul    ecx, sizeof.ehci_static_ep

        mov     [.variant_delta], ecx

; 2b. [.target_delta] is delta between the final answer from the group

; corresponding to [.interval] and the item from the first group.

        sub     eax, ecx

        sub     eax, ecx

        mov     [.target_delta], eax

; 2c. [.variant] is the first list from the first group that corresponds

; to the current variant.

        lea     eax, [esi+ehci_controller.IntEDs-sizeof.ehci_controller]

        mov     [.variant], eax

; 2d. [.tthub] identifies TT hub for new pipe, [.new_budget] is FS budget

; for new pipe.

        mov     eax, [edi+usb_pipe.DeviceData]

        mov     eax, [eax+usb_device_data.TTHub]

        mov     ebx, edi

        mov     [.tthub], eax

        call    tt_calc_budget

        mov     [.new_budget], ax

; 2e. [.usb_split_info] describes bandwidth used by new pipe on HS bus.

        lea     edi, [.info]

        call    tt_fill_split_info

        test    eax, eax

        jz      .no_bandwidth

; 2f. There is no best variant yet, put maximal possible values,

; so any variant would be better than the "current".

        or      [.best_fs_bandwidth], -1

        or      [.target], -1

        or      [.bandwidth], -1

        or      [.targetsmask], -1

; 3. Loop over all variants, for every variant decide whether it is acceptable,

; select the best variant from all acceptable variants.

.check_variants:

        tt_calc_statistics_for_one_variant

        xor     ecx, ecx

.check_microframes:

        tt_check_variant_microframe

        inc     ecx

        cmp     ecx, 6

        jb      .check_microframes

        add     [.variant], sizeof.ehci_static_ep

        dec     [.interval]

        jnz     .check_variants

; 4. If there is no acceptable variants, return error.

        mov     ecx, [.targetsmask]

        mov     edx, [.target]

        cmp     ecx, -1

        jz      .no_bandwidth

; 5. Calculate the answer: edx -> selected list, eax = S-Mask and C-Mask.

        mov     eax, [.info.microframe_mask]

        add     edx, [.target_delta]

        shl     eax, cl

        and     eax, 0xFFFF

; 6. Update HS bandwidths in the selected list.

        xor     ecx, ecx

        mov     ebx, [.info.ssplit_bandwidth]

.update_ssplit:

        bt      eax, ecx

        jnc     @f

        add     [edx+ehci_static_ep.Bandwidths+ecx*2], bx

@@:

        inc     ecx

        cmp     ecx, 8

        jb      .update_ssplit

        mov     ebx, [.info.csplit_bandwidth]

.update_csplit:

        bt      eax, ecx

        jnc     @f

        add     [edx+ehci_static_ep.Bandwidths+(ecx-8)*2], bx

@@:

        inc     ecx

        cmp     ecx, 16

        jb      .update_csplit

; 7. Return.

        add     edx, ehci_static_ep.SoftwarePart

        pop     edi ebx

        ret

.no_bandwidth:

        dbgstr 'Periodic bandwidth limit reached'

        xor     eax, eax

        xor     edx, edx

        pop     edi ebx

        ret

endp

; Pipe is removing, update the corresponding lists.

; We do not reorder anything, so just update book-keeping variable

; in the list header.

proc ehci_fs_interrupt_list_unlink

; calculate bandwidth

        push    edi

        sub     esp, sizeof.usb_split_info

        mov     edi, esp

        call    tt_fill_split_info

; get target list

        mov     edx, [ebx+usb_pipe.BaseList]

; update bandwidth for Start-Split

        mov     eax, [edi+usb_split_info.ssplit_bandwidth]

        xor     ecx, ecx

.dec_bandwidth_1:

        bt      [ebx+ehci_pipe.Flags-sizeof.ehci_pipe], ecx

        jnc     @f

        sub     word [edx+ecx*2+ehci_static_ep.Bandwidths - ehci_static_ep.SoftwarePart], ax

@@:

        inc     ecx

        cmp     ecx, 8

        jb      .dec_bandwidth_1

; update bandwidth for Complete-Split

        mov     eax, [edi+usb_split_info.csplit_bandwidth]

.dec_bandwidth_2:

        bt      [ebx+ehci_pipe.Flags-sizeof.ehci_pipe], ecx

        jnc     @f

        sub     word [edx+(ecx-8)*2+ehci_static_ep.Bandwidths - ehci_static_ep.SoftwarePart], ax

@@:

        inc     ecx

        cmp     ecx, 16

        jb      .dec_bandwidth_2

        add     esp, sizeof.usb_split_info

        pop     edi

        ret

endp

; Helper procedure for ehci_select_tt_interrupt_list.

; Calculates "best-case budget" according to the core spec,

; that is, number of bytes (not bits) corresponding to "optimistic" transaction

; time, including inter-packet delays/bus turn-around time,

; but without bit stuffing and timers drift.

; One extra TT-specific delay is added: TT think time from the hub descriptor.

; Similar to calc_usb1_bandwidth with corresponding changes.

; eax -> usb_hub with TT, ebx -> usb_pipe

proc tt_calc_budget

        invoke  usbhc_api.usb_get_tt_think_time ; ecx = TT think time in FS-bytes

        mov     eax, [ebx+ehci_pipe.Token-sizeof.ehci_pipe]

        shr     eax, 16

        and     eax, (1 shl 11) - 1     ; get data length

        bt      [ebx+ehci_pipe.Token-sizeof.ehci_pipe], 12

        jc      .low_speed

; Full-speed interrupt IN/OUT:

; 33 bits for Token packet (8 for SYNC, 24 for token+address, 3 for EOP),

; 18 bits for bus turn-around, 11 bits for SYNC+EOP in Data packet,

; 2 bits for inter-packet delay, 19 bits for Handshake packet,

; 2 bits for another inter-packet delay. 85 bits total, pad to 11 bytes.

        lea     eax, [eax+11+ecx]

; 1 byte is minimal TT think time in addition to ecx.

        ret

.low_speed:

; Low-speed interrupt IN/OUT:

; multiply by 8 for LS -> FS,

; add 85 bytes as in full-speed interrupt and extra 5 bytes for two PRE packets

; and two hub delays.

; 1 byte is minimal TT think time in addition to ecx.

        lea     eax, [eax*8+90+ecx]

        ret

endp

; Helper procedure for TT scheduler.

; Calculates Start-Split/Complete-Split masks and HS bandwidths.

; ebx -> usb_pipe, edi -> usb_split_info

proc tt_fill_split_info

; Interrupt endpoints.

; The core spec says in 5.7.3 "Interrupt Transfer Packet Size Constraints" that:

; The maximum allowable interrupt data payload size is 64 bytes or less for full-speed.

; Low-speed devices are limited to eight bytes or less maximum data payload size.

; This is important for scheduling, it guarantees that in any case transaction fits

; in two microframes (usually one, two if transaction has started too late in the first

; microframe), so check it.

        mov     eax, [ebx+ehci_pipe.Token-sizeof.ehci_pipe]

        mov     ecx, 8

        bt      eax, 12

        jc      @f

        mov     ecx, 64

@@:

        shr     eax, 16

        and     eax, (1 shl 11) - 1     ; get data length

        cmp     eax, ecx

        ja      .error

        add     eax, 3  ; add 3 bytes for other fields in data packet, PID+CRC16

; Multiply by 8 for bytes -> bits and then by 7/6 to accomodate bit stuffing;

; total 28/3 = 9+1/3

        mov     edx, 55555556h

        lea     ecx, [eax*9]

        mul     edx

; One start-split, three complete-splits (unless the last is too far,

; but this is handled by the caller).

        mov     eax, [ebx+usb_pipe.LastTD]

        mov     [edi+usb_split_info.microframe_mask], 0x1C01

; Structure and HS bandwidth of packets depends on the direction.

        bt      [eax+ehci_gtd.Token-sizeof.ehci_gtd], 8

        jc      .interrupt_in

.interrupt_out:

; Start-Split phase:

; 77 bits for SPLIT packet (32 for SYNC, 8 for EOP, 32 for data, 5 for bit stuffing),

; 88 bits for inter-packet delay, 68 bits for Token packet,

; 88 bits for inter-packet delay, 40 bits for SYNC+EOP in Data packet,

; 88 bits for last inter-packet delay, total 449 bits.

        lea     eax, [edx+ecx+449]

        mov     [edi+usb_split_info.ssplit_bandwidth], eax

; Complete-Split phase:

; 77 bits for SPLIT packet,

; 88 bits for inter-packet delay, 68 bits for Token packet,

; 736 bits for bus turn-around, 49 bits for Handshake packet,

; 8 bits for inter-packet delay, total 1026 bits.

        mov     [edi+usb_split_info.csplit_bandwidth], 1026

        ret

.interrupt_in:

; Start-Split phase:

; 77 bits for SPLIT packet, 88 bits for inter-packet delay,

; 68 bits for Token packet, 88 bits for another inter-packet delay,

; total 321 bits.

        mov     [edi+usb_split_info.ssplit_bandwidth], 321

; Complete-Split phase:

; 77 bits for SPLIT packet, 88 bits for inter-packet delay,

; 68 bits for Token packet, 736 bits for bus turn-around,

; 40 bits for SYNC+EOP in Data packet, 8 bits for inter-packet delay,

; total 1017 bits.

        lea     eax, [edx+ecx+1017]

        mov     [edi+usb_split_info.csplit_bandwidth], eax

        ret

.error:

        xor     eax, eax

        ret

endp