Re: Intel HDMI probe regression on IVB (and older?)

[Takashi Iwai <tiwai@suse.de>]

On Mon, 20 Jun 2022 11:26:52 +0200,
Kai Vehmanen wrote:
> 
> Hi,
> 
> On Mon, 20 Jun 2022, Takashi Iwai wrote:
> 
> > we've got a regression report about Intel HDMI.  It seems that the
> > recent change to skip the component binding (commit c9db8a30d9f0)
> > throws away the devices incorrectly on IvyBridge.  I guess the similar
> > issue could happen on older chips.  The bug report is found at
> >   https://bugzilla.opensuse.org/show_bug.cgi?id=1200611
> 
> we'll check. We actually have IVB (and older), in the i915 CI and I can 
> see the binding check working correctly there (with 5.19-rc2). But 
> obviously something goes wrong in the reporter's case, so needs more 
> debug.

So this looks like a bug due to the use of pci_get_class().
Since there is no pci_get_base_class(), we likely need to open-code
the search, e.g. something like below.


Takashi

-- 8< --
From: Takashi Iwai <tiwai@suse.de>
Subject: [PATCH] ALSA: hda: Fix discovery of i915 graphics PCI device

It's been reported that the recent fix for skipping the
component-binding with D-GPU caused a regression on some systems; it
resulted in the completely missing component binding with i915 GPU.

The problem was the use of pci_get_class() function.  It matches with
the full PCI class bits, while we want to match only partially the PCI
base class bits.  So, when a system has an i915 graphics device with
the PCI class 0380, it won't hit because we're looking for only the
PCI class 0300.

This patch fixes i915_gfx_present() to look up each PCI device and
match with PCI base class explicitly instead of pci_get_class().

Fixes: c9db8a30d9f0 ("ALSA: hda/i915 - skip acomp init if no matching display")
Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1200611
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/hda/hdac_i915.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/sound/hda/hdac_i915.c b/sound/hda/hdac_i915.c
index 3f35972e1cf7..161a9711cd63 100644
--- a/sound/hda/hdac_i915.c
+++ b/sound/hda/hdac_i915.c
@@ -119,21 +119,18 @@ static int i915_component_master_match(struct device *dev, int subcomponent,
 /* check whether Intel graphics is present and reachable */
 static int i915_gfx_present(struct pci_dev *hdac_pci)
 {
-	unsigned int class = PCI_BASE_CLASS_DISPLAY << 16;
 	struct pci_dev *display_dev = NULL;
-	bool match = false;
 
-	do {
-		display_dev = pci_get_class(class, display_dev);
-
-		if (display_dev && display_dev->vendor == PCI_VENDOR_ID_INTEL &&
+	for_each_pci_dev(display_dev) {
+		if (display_dev->vendor == PCI_VENDOR_ID_INTEL &&
+		    (display_dev->class >> 16) == PCI_BASE_CLASS_DISPLAY &&
 		    connectivity_check(display_dev, hdac_pci)) {
 			pci_dev_put(display_dev);
-			match = true;
+			return true;
 		}
-	} while (!match && display_dev);
+	}
 
-	return match;
+	return false;
 }
 
 /**
-- 
2.35.3