Re: [PATCH v2 10/11] PCI: Stop caching ATS Invalidate Queue Depth

[Don Dutile <ddutile@redhat.com>]

On 07/20/2015 08:15 PM, Bjorn Helgaas wrote:
> Stop caching the Invalidate Queue Depth in struct pci_dev.
> pci_ats_queue_depth() is typically called only once per device, and it
> returns a fixed value per-device, so callers who need the value frequently
> can cache it themselves.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---
>   drivers/pci/ats.c   |    9 ++++-----
>   include/linux/pci.h |    1 -
>   2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index 67524a7..bdb1383 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -20,16 +20,12 @@
>   void pci_ats_init(struct pci_dev *dev)
>   {
>   	int pos;
> -	u16 cap;
>
>   	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ATS);
>   	if (!pos)
>   		return;
>
>   	dev->ats_cap = pos;
> -	pci_read_config_word(dev, dev->ats_cap + PCI_ATS_CAP, &cap);
> -	dev->ats_qdep = PCI_ATS_CAP_QDEP(cap) ? PCI_ATS_CAP_QDEP(cap) :
> -					    PCI_ATS_MAX_QDEP;
>   }
>
>   /**
> @@ -131,13 +127,16 @@ EXPORT_SYMBOL_GPL(pci_restore_ats_state);
>    */
>   int pci_ats_queue_depth(struct pci_dev *dev)
>   {
> +	u16 cap;
> +
>   	if (!dev->ats_cap)
>   		return -EINVAL;
>
>   	if (dev->is_virtfn)
>   		return 0;
>
hmmm, isn't one of the fixes in this patch set to
change the caching of ats queue depth ?  won't above
make it 0 for all VF's ?  is that correct, or desired (virtual) value?

> -	return dev->ats_qdep;
> +	pci_read_config_word(dev, dev->ats_cap + PCI_ATS_CAP, &cap);
> +	return PCI_ATS_CAP_QDEP(cap) ? PCI_ATS_CAP_QDEP(cap) : PCI_ATS_MAX_QDEP;
>   }
>   EXPORT_SYMBOL_GPL(pci_ats_queue_depth);
>
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 307f96a..4b484fd 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -378,7 +378,6 @@ struct pci_dev {
>   	};
>   	u16		ats_cap;	/* ATS Capability offset */
>   	u8		ats_stu;	/* ATS Smallest Translation Unit */
> -	u8		ats_qdep;	/* ATS Invalidate Queue Depth */
>   	atomic_t	ats_ref_cnt;	/* number of VFs with ATS enabled */
>   #endif
>   	phys_addr_t rom; /* Physical address of ROM if it's not from the BAR */
>
> --
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