Re: [PATCH] Fix intel_detect_pch() to work in xen environment.

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Jun 18, 2013 at 08:54:35PM +0800, G.R. wrote:
> On Sun, Dec 23, 2012 at 2:51 PM, G.R. <firemeteor@users.sourceforge.net> wrote:
> >>> Hi Jesse, I think I need to resend the patch with proper comment to
> >>> have it formally accepted.
> >>> Any guide line for formal patch submission? Do I need to start a
> >>> separate thread?
> >>
> >> No, just cc Daniel Vetter.
> >>
> >> --
> >> Jesse Barnes, Intel Open Source Technology Center
> >
> > Thanks,
> > Resend with updated patch && Daniel involved.
> > Also include the background info for easy reading.
> >
> > In XEN HVM guest, there is always an emulated PIIX3 ISA bridge on slot 01.0.
> > This shadows the PCH ISA bridge on 1f.0 with the current
> > intel_detect_pch() implementation.
> > The issue can be easily solved by looping through all the ISA bridges
> > until the first match is found, instead of just check against the
> > first one.
> >
> 
> This seems to have lost in the list. Retry it again with latest
> torvalds' kernel:

> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index a2e4953..e38fa86 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -454,11 +454,18 @@ void intel_detect_pch(struct drm_device *dev)
>          * make graphics device passthrough work easy for VMM, that only
>          * need to expose ISA bridge to let driver know the real hardware
>          * underneath. This is a requirement from virtualization team.
> +        *
> +        * In some virtualized environments (e.g. XEN), there is irrelevant
> +        * ISA bridge in the system. To work reliably, we should scan trhough
> +        * all the ISA bridge devices and check for the first match, instead
> +        * of only checking the first one.
>          */
>         pch = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, NULL);
> -       if (pch) {
> +       while (pch) {
> +               struct pci_dev * curr = pch;
                                  ^

No space there. I think checkpatch should catch that.

>                 if (pch->vendor == PCI_VENDOR_ID_INTEL) {
>                         unsigned short id;
> +                       unsigned found = 1;

bool found = true;

Although it would be easy to adjust the patch to not need a 'found'
variable.

>                         id = pch->device & INTEL_PCH_DEVICE_ID_MASK;
>                         dev_priv->pch_id = id;
> 
> @@ -490,10 +497,20 @@ void intel_detect_pch(struct drm_device *dev)
>                                 DRM_DEBUG_KMS("Found LynxPoint LP PCH\n");
>                                 WARN_ON(!IS_HASWELL(dev));
>                                 WARN_ON(!IS_ULT(dev));
> +                       } else {
> +                               found = 0;
> +                       }
> +                       if (found) {
> +                               BUG_ON(dev_priv->num_pch_pll > I915_NUM_PLLS);
> +                               pci_dev_put(pch);
> +                               break;
>                         }
> -                       BUG_ON(dev_priv->num_pch_pll > I915_NUM_PLLS);
>                 }
> -               pci_dev_put(pch);
> +               pch = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, curr);
> +               pci_dev_put(curr);
> +       }
> +       if (!pch) {
> +               DRM_DEBUG_KMS("No PCH found?\n");
>         }
>  }
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-- 
Ville Syrjälä
Intel OTC