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static inline __attribute__((const))

bool is_power_of_2(unsigned long n)

{

    return (n != 0 && ((n & (n - 1)) == 0));

}

int pcie_capability_clear_and_set_word(struct pci_dev *dev, int pos,

                                       u16 clear, u16 set)

{

        int ret;

        u16 val;

        ret = pcie_capability_read_word(dev, pos, &val);

        if (!ret) {

                val &= ~clear;

                val |= set;

                ret = pcie_capability_write_word(dev, pos, val);

        }

        return ret;

}

int pcie_get_readrq(struct pci_dev *dev)

{

        u16 ctl;

        pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &ctl);

        return 128 << ((ctl & PCI_EXP_DEVCTL_READRQ) >> 12);

}

EXPORT_SYMBOL(pcie_get_readrq);

/**

 * pcie_set_readrq - set PCI Express maximum memory read request

 * @dev: PCI device to query

 * @rq: maximum memory read count in bytes

 *    valid values are 128, 256, 512, 1024, 2048, 4096

 *

 * If possible sets maximum memory read request in bytes

 */

int pcie_set_readrq(struct pci_dev *dev, int rq)

{

        u16 v;

        if (rq < 128 || rq > 4096 || !is_power_of_2(rq))

                return -EINVAL;

        v = (ffs(rq) - 8) << 12;

        return pcie_capability_clear_and_set_word(dev, PCI_EXP_DEVCTL,

                                                  PCI_EXP_DEVCTL_READRQ, v);

}