Re: [PATCH v4 2/7] PCI/ATS: Initialize PRI in pci_ats_init()

[sathyanarayanan kuppuswamy]

Hi Keith,

Thanks for the review.

On 8/1/19 2:09 PM, Keith Busch wrote:
> On Wed, Jul 03, 2019 at 01:46:19PM -0700, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
> > +#ifdef CONFIG_PCI_PRI
> > +static void pci_pri_init(struct pci_dev *pdev)
> > +{
> > +	u32 max_requests;
> > +	int pos;
> > +
> > +	/*
> > +	 * As per PCIe r4.0, sec 9.3.7.11, only PF is permitted to
> > +	 * implement PRI and all associated VFs can only use it.
> > +	 * Since PF already initialized the PRI parameters there is
> > +	 * no need to proceed further.
> > +	 */
> > +	if (pdev->is_virtfn)
> > +		return;
> > +
> > +	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
> > +	if (!pos)
> > +		return;
> > +
> > +	pci_read_config_dword(pdev, pos + PCI_PRI_MAX_REQ, &max_requests);
> > +
> > +	/*
> > +	 * Since PRI is a shared resource between PF and VF, we must not
> > +	 * configure Outstanding Page Allocation Quota as a per device
> > +	 * resource in pci_enable_pri(). So use maximum value possible
> > +	 * as default value.
> > +	 */
> > +	pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, max_requests);
> > +
> > +	pdev->pri_reqs_alloc = max_requests;
> > +	pdev->pri_cap = pos;
> > +}
> > +#endif
> > +
> >   void pci_ats_init(struct pci_dev *dev)
> >   {
> >   	int pos;
> > @@ -28,6 +62,10 @@ void pci_ats_init(struct pci_dev *dev)
> >   		return;
> >   
> >   	dev->ats_cap = pos;
> > +
> > +#ifdef CONFIG_PCI_PRI
> > +	pci_pri_init(dev);
> > +#endif
> >   }
> Rather than surround the call to pci_pri_init() with the #ifdef, you
> should provide an empty function implementation when CONFIG_PCI_PRI is
> not defined. Same thing for the next patch adding PASID.
This function is defined and used in the same file (ats.c). Is there any 
advantage in defining an empty function ? But if this is the recommended 
approach, I can make the necessary changes. Please confirm.
>
--
Sathyanarayanan Kuppuswamy
Linux kernel developer