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SubjectRe: [PATCH 1/2] PCI-X/PCI-Express read control interfaces
On Tue, 15 May 2007 13:59:13 +0200 Peter Oruba wrote:

> This patch introduces an interface to read and write PCI-X / PCI-Express
> maximum read byte count values from PCI config space. There is a second
> function that returns the maximum _designed_ read byte count, which marks the
> maximum value for a device, since some drivers try to set MMRBC to the
> highest allowed value and rely on such a function.
>
> Signed-off by: Peter Oruba <peter.oruba@amd.com>
> Based on patch set by Stephen Hemminger <shemminger@linux-foundation.org>
>
> ---
> diff -uprN -X linux-2.6.22-rc1.orig/Documentation/dontdiff
> linux-2.6.22-rc1.orig/drivers/pci/pci.c linux-2.6.22-rc1/drivers/pci/pci.c
> --- linux-2.6.22-rc1.orig/drivers/pci/pci.c 2007-05-14 11:29:39.473498000
> +0200
> +++ linux-2.6.22-rc1/drivers/pci/pci.c 2007-05-15 11:44:33.804254000 +0200
> @@ -1375,6 +1375,170 @@ pci_set_consistent_dma_mask(struct pci_d
> #endif
>
> /**
> + * pcix_get_max_mmrbc - get PCI-X maximum designed memory read byte count
> + * @dev: PCI device to query
> + *
> + * Returns mmrbc: maximum designed memory read count in bytes
> + * or appropriate error value.
> + */
> +int
> +pcix_get_max_mmrbc(struct pci_dev *dev)

Kernel style is like so (referring to multiple occurrences):

int pcix_get_max_mmrbc(struct pci_dev *dev)

Yes, that source file does it both ways (and needs to be Fixed).


> +{
> + int ret, err, cap;
> + u32 stat;
> +
> + cap = pci_find_capability(dev, PCI_CAP_ID_PCIX);
> + if (!cap)
> + return -EINVAL;
> +
> + err = pci_read_config_dword(dev, cap + PCI_X_STATUS, &stat);
> + if (err)
> + return -EINVAL;
> +
> + ret = (stat & PCI_X_STATUS_MAX_READ) >> 12;
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(pcix_get_max_mmrbc);
> +
> +
> +/**
> + * pcix_set_mmrbc - set PCI-X maximum memory read byte count
> + * @dev: PCI device to query
> + * @mmrbc: maximum memory read count in bytes
> + * valid values are 512, 1024, 2048, 4096
> + *
> + * If possible sets maximum memory read byte count, some bridges have erratas

"errata" is plural.

> + * that prevent this.
> + */
> +int
> +pcix_set_mmrbc(struct pci_dev *dev, int mmrbc)
> +{
...
> +}
> +EXPORT_SYMBOL(pcix_set_mmrbc);
> +
> +/**
> + * pcie_get_readrq - get PCI Express read request size
> + * @dev: PCI device to query
> + *
> + * Returns maximum memory read request in bytes
> + * or appropriate error value.
> + */
> +int pcie_get_readrq(struct pci_dev *dev)

:)

> +{
> + int ret, cap;
> + u16 ctl;
> +
> + cap = pci_find_capability(dev, PCI_CAP_ID_EXP);
> + if (!cap)
> + return -EINVAL;
> +
> + ret = pci_read_config_word(dev, cap + PCI_EXP_DEVCTL, &ctl);
> + if (!ret)
> + ret = 128 << ((ctl & PCI_EXP_DEVCTL_READRQ) >> 12);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(pcie_get_readrq);
> +


---
~Randy
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