; Implementation of periodic transaction scheduler for USB.
; Bandwidth dedicated to periodic transactions is limited, so
; different pipes should be scheduled as uniformly as possible.
; USB1 scheduler.
; Algorithm is simple:
; when adding a pipe, optimize the following quantity:
; * for every millisecond, take all bandwidth scheduled to periodic transfers,
; * calculate maximum over all milliseconds,
; * select a variant which minimizes that maximum;
; when removing a pipe, do nothing (except for bookkeeping).
; sanity check: structures in UHCI and OHCI should be the same
if (sizeof.ohci_static_ep=sizeof.uhci_static_ep)&(ohci_static_ep.SoftwarePart=uhci_static_ep.SoftwarePart)&(ohci_static_ep.NextList=uhci_static_ep.NextList)
; Select a list for a new pipe.
; in: esi -> usb_controller, maxpacket, type, interval can be found in the stack
; in: ecx = 2 * maximal interval = total number of periodic lists + 1
; in: edx -> {u|o}hci_static_ep for the first list
; in: eax -> byte past {u|o}hci_static_ep for the last list in the first group
; out: edx -> usb_static_ep for the selected list or zero if failed
proc usb1_select_interrupt_list
; inherit some variables from usb_open_pipe
virtual at ebp-8
.bandwidth dd ?
.target dd ?
dd ?
dd ?
.config_pipe dd ?
.endpoint dd ?
.maxpacket dd ?
.type dd ?
.interval dd ?
end virtual
push ebx edi ; save used registers to be stdcall
push eax ; save eax for checks in step 3
; 1. Only intervals 2^k ms can be supported.
; The core specification says that the real interval should not be greater
; than the interval given by the endpoint descriptor, but can be less.
; Determine the actual interval as 2^k ms.
mov eax, ecx
; 1a. Set [.interval] to 1 if it was zero; leave it as is otherwise
cmp [.interval], 1
adc [.interval], 0
; 1b. Divide ecx by two while it is strictly greater than [.interval].
@@:
shr ecx, 1
cmp [.interval], ecx
jb @b
; ecx = the actual interval
;
; For example, let ecx = 8, eax = 64.
; The scheduler space is 32 milliseconds,
; we need to schedule something every 8 ms;
; there are 8 variants: schedule at times 0,8,16,24,
; schedule at times 1,9,17,25,..., schedule at times 7,15,23,31.
; Now concentrate: there are three nested loops,
; * the innermost loop calculates the total periodic bandwidth scheduled
; in the given millisecond,
; * the intermediate loop calculates the maximum over all milliseconds
; in the given variant, that is the quantity we're trying to minimize,
; * the outermost loop checks all variants.
; 2. Calculate offset between the first list and the first list for the
; selected interval, in bytes; save in the stack for step 4.
sub eax, ecx
sub eax, ecx
imul eax, sizeof.ohci_static_ep
push eax
imul ebx, ecx, sizeof.ohci_static_ep
; 3. Select the best variant.
; 3a. The outermost loop.
; Prepare for the loop: set the current optimal bandwidth to maximum
; possible value (so that any variant will pass the first comparison),
; calculate delta for the intermediate loop.
or [.bandwidth], -1
.varloop:
; 3b. The intermediate loop.
; Prepare for the loop: set the maximum to be calculated to zero,
; save counter of the outermost loop.
xor edi, edi
push edx
virtual at esp
.cur_variant dd ? ; step 3b
.result_delta dd ? ; step 2
.group1_limit dd ? ; function prolog
end virtual
.calc_max_bandwidth:
; 3c. The innermost loop. Sum over all lists.
xor eax, eax
push edx
.calc_bandwidth:
add eax, [edx+ohci_static_ep.SoftwarePart+usb_static_ep.Bandwidth]
mov edx, [edx+ohci_static_ep.NextList]
test edx, edx
jnz .calc_bandwidth
pop edx
; 3d. The intermediate loop continued: update maximum.
cmp eax, edi
jb @f
mov edi, eax
@@:
; 3e. The intermediate loop continued: advance counter.
add edx, ebx
cmp edx, [.group1_limit]
jb .calc_max_bandwidth
; 3e. The intermediate loop done: restore counter of the outermost loop.
pop edx
; 3f. The outermost loop continued: if the current variant is
; better (maybe not strictly) then the previous optimum, update
; the optimal bandwidth and resulting list.
cmp edi, [.bandwidth]
ja @f
mov [.bandwidth], edi
mov [.target], edx
@@:
; 3g. The outermost loop continued: advance counter.
add edx, sizeof.ohci_static_ep
dec ecx
jnz .varloop
; 4. Get the pointer to the best list.
pop edx ; restore value from step 2
pop eax ; purge stack var from prolog
add edx, [.target]
; 5. Calculate bandwidth for the new pipe.
mov eax, [.maxpacket] ; TODO: calculate real bandwidth
and eax, (1 shl 11) - 1
; 6. TODO: check that bandwidth for the new pipe plus old bandwidth
; still fits to maximum allowed by the core specification.
; 7. Convert {o|u}hci_static_ep to usb_static_ep, update bandwidth and return.
add edx, ohci_static_ep.SoftwarePart
add [edx+usb_static_ep.Bandwidth], eax
pop edi ebx ; restore used registers to be stdcall
ret
endp
; sanity check, part 2
else
.err select_interrupt_list must be different for UHCI and OHCI
end if
; Pipe is removing, update the corresponding lists.
; We do not reorder anything, so just update book-keeping variable
; in the list header.
proc usb1_interrupt_list_unlink
virtual at esp
dd ? ; return address
.maxpacket dd ?
.lowspeed db ?
.direction db ?
rb 2
end virtual
; find list header
mov edx, ebx
@@:
mov edx, [edx+usb_pipe.NextVirt]
cmp [edx+usb_pipe.Controller], esi
jnz @b
; subtract pipe bandwidth
; TODO: calculate real bandwidth
mov eax, [.maxpacket]
and eax, (1 shl 11) - 1
sub [edx+usb_static_ep.Bandwidth], eax
ret 8
endp
; USB2 scheduler.
; There are two parts: high-speed pipes and split-transaction pipes.
; Split-transaction scheduler is currently a stub.
; 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 microframe,
; * select a variant which minimizes that maximum;
; 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
push 5
pop ecx
@@:
; 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
push 1
pop ebx
push sizeof.ehci_static_ep
pop edx
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
mov [.bandwidth], edi
mov [.target], edx
push 1
pop eax
shl eax, cl
mov [.targetsmask], eax
@@:
; 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. 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]
; 6. Calculate bandwidth for the new pipe.
; TODO1: calculate real bandwidth
mov eax, [.maxpacket]
mov ecx, eax
and eax, (1 shl 11) - 1
shr ecx, 11
inc ecx
and ecx, 3
imul eax, ecx
; 7. TODO2: 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
; 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
push 1
pop eax
shl eax, cl
pop edi ebx ; restore used registers to be stdcall
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
push 0x11
pop edx
cmp ecx, 1
ja @f
mov dl, 0x55
jz @f
mov dl, 0xFF
@@:
; try all variants edx, edx shl 1, edx shl 2, ...
; until 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. TODO1: calculate real bandwidth.
mov eax, [.maxpacket]
mov ecx, eax
and eax, (1 shl 11) - 1
shr ecx, 11
inc ecx
and ecx, 3
imul eax, ecx
; 14. TODO2: check that current [.bandwidth] + new bandwidth <= limit;
; USB2 specification allows maximum 60000*80% bit times for periodic microframe.
; 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
; 15. 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
; get target list
mov edx, [ebx+ehci_pipe.BaseList-ehci_pipe.SoftwarePart]
; TODO: calculate real bandwidth
movzx eax, word [ebx+ehci_pipe.Token-ehci_pipe.SoftwarePart+2]
mov ecx, [ebx+ehci_pipe.Flags-ehci_pipe.SoftwarePart]
and eax, (1 shl 11) - 1
shr ecx, 30
imul eax, ecx
movzx ecx, byte [ebx+ehci_pipe.Flags-ehci_pipe.SoftwarePart]
add edx, ehci_static_ep.Bandwidths - ehci_static_ep.SoftwarePart
; update bandwidth
.dec_bandwidth:
shr ecx, 1
jnc @f
sub [edx], ax
@@:
add edx, 2
test ecx, ecx
jnz .dec_bandwidth
; return
ret
endp
uglobal
ehci_last_fs_alloc dd ?
endg
; This needs to be rewritten. Seriously.
; It schedules everything to the first microframe of some frame,
; frame is spinned out of thin air.
; This works while you have one keyboard and one mouse...
; maybe even ten keyboards and ten mice... but give any serious stress,
; and this would break.
proc ehci_select_fs_interrupt_list
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
cmp [.interval], 1
adc [.interval], 0
mov ecx, 64
mov eax, ecx
@@:
shr ecx, 1
cmp [.interval], ecx
jb @b
sub eax, ecx
sub eax, ecx
dec ecx
and ecx, [ehci_last_fs_alloc]
inc [ehci_last_fs_alloc]
add eax, ecx
imul eax, sizeof.ehci_static_ep
lea edx, [esi+ehci_controller.IntEDs.SoftwarePart+eax-sizeof.ehci_controller]
mov ax, 1C01h
ret
endp
proc ehci_fs_interrupt_list_unlink
ret
endp