Hi Kuppuswamy,
Previous changes to ats.c used subject lines starting with just
"PCI:".
I think it does make sense to include "ATS", but please do it in
the way we do it for other PCI features, e.g.,
PCI/ATS: Add pci_ats_page_aligned() interface
On Thu, Feb 07, 2019 at 10:41:13AM -0800,
sathyanarayanan.kuppusw...@linux.intel.com wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppusw...@linux.intel.com>
>
> Add a new function to return the status of ATS page aligned request
> bit in ATS capability register. This function will be used by
> drivers like IOMMU, if it is required to enforce page-aligned
> requests in ATS.
"return the Page Aligned Request bit in the ATS Capability Register"
This is just to make the terminology match the PCIe spec exactly so
it's easier to look up.
> Cc: Ashok Raj <ashok....@intel.com>
> Cc: Jacob Pan <jacob.jun....@linux.intel.com>
> Cc: Keith Busch <keith.bu...@intel.com>
> Suggested-by: Ashok Raj <ashok....@intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan
> <sathyanarayanan.kuppusw...@linux.intel.com>
> ---
> drivers/pci/ats.c | 22 ++++++++++++++++++++++
> include/linux/pci.h | 2 ++
> include/uapi/linux/pci_regs.h | 1 +
> 3 files changed, 25 insertions(+)
>
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index 5b78f3b1b918..7d14b9a1981e 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -142,6 +142,28 @@ int pci_ats_queue_depth(struct pci_dev *dev)
> }
> EXPORT_SYMBOL_GPL(pci_ats_queue_depth);
>
> +/**
> + * pci_ats_page_aligned - Return ATS page aligned request bit status.
Capitalize name of bit as above.
> + * @pdev: the PCI device
> + *
> + * Returns value > 0 if address is aligned or 0 otherwise.
s/ / /
"if Untranslated Addresses generated by the device are always
aligned or ..."
> + *
> + * As per PCI spec, If page aligned request bit is set, it indicates
> + * the untranslated address is always aligned to a 4096 byte boundary.
"Per PCIe r4.0, sec 10.5.1.2, if the Page Aligned Request bit,
Untranslated Addresses generated by the device are always aligned to a
4096 byte boundary."
> + */
> +int pci_ats_page_aligned(struct pci_dev *pdev)
> +{
> + u16 cap;
> +
> + if (!pdev->ats_cap)
> + return 0;
> +
> + pci_read_config_word(pdev, pdev->ats_cap + PCI_ATS_CAP, &cap);
> +
> + return PCI_ATS_CAP_PAGE_ALIGNED(cap);
> +}
> +EXPORT_SYMBOL_GPL(pci_ats_page_aligned);
> +
> #ifdef CONFIG_PCI_PRI
> /**
> * pci_enable_pri - Enable PRI capability
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 65f1d8c2f082..9724a8c0496b 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1524,11 +1524,13 @@ void pci_ats_init(struct pci_dev *dev);
> int pci_enable_ats(struct pci_dev *dev, int ps);
> void pci_disable_ats(struct pci_dev *dev);
> int pci_ats_queue_depth(struct pci_dev *dev);
> +int pci_ats_page_aligned(struct pci_dev *dev);
> #else
> static inline void pci_ats_init(struct pci_dev *d) { }
> static inline int pci_enable_ats(struct pci_dev *d, int ps) { return
> -ENODEV; }
> static inline void pci_disable_ats(struct pci_dev *d) { }
> static inline int pci_ats_queue_depth(struct pci_dev *d) { return -ENODEV; }
> +static inline int pci_ats_page_aligned(struct pci_dev *dev) { return 0; }
> #endif
>
> #ifdef CONFIG_PCIE_PTM
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index e1e9888c85e6..d42a759867b8 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -866,6 +866,7 @@
> #define PCI_ATS_CAP 0x04 /* ATS Capability Register */
> #define PCI_ATS_CAP_QDEP(x) ((x) & 0x1f) /* Invalidate Queue Depth */
> #define PCI_ATS_MAX_QDEP 32 /* Max Invalidate Queue Depth */
> +#define PCI_ATS_CAP_PAGE_ALIGNED(x) 0x0020 /* Page Aligned Request */
This is wrong because it *always* returns "true", regardless of the
value of the ATS Capability register.
I would prefer this:
#define PCI_ATS_CAP_PAGE_ALIGNED 0x0020
and then test it like this:
if (cap & PCI_ATS_CAP_PAGE_ALIGNED)
return 1;
return 0;
> #define PCI_ATS_CTRL 0x06 /* ATS Control Register */
> #define PCI_ATS_CTRL_ENABLE 0x8000 /* ATS Enable */
> #define PCI_ATS_CTRL_STU(x) ((x) & 0x1f) /* Smallest Translation Unit */
> --
> 2.20.1
>
