[alsa-devel] [PATCH] ALSA: hda - PCH HDA controller not controlled by i915 power

[Takashi Iwai]

At Tue, 09 Jun 2015 08:46:35 +0200,
David Henningsson wrote:
> 
> 
> 
> On 2015-06-09 08:31, Takashi Iwai wrote:
> > At Tue,  9 Jun 2015 14:05:18 +0800,
> > libin.yang at intel.com wrote:
> >>
> >> From: Libin Yang <libin.yang at intel.com>
> >>
> >> On some Intel platforms, the HDMI codec is connected to PCH HDA
> >> controller. In this case, AZX_DCAPS_I915_POWERWELL is set and
> >> the i915 power well failure should not block the hda controller
> >> initialization.
> >>
> >> Signed-off-by: Libin Yang <libin.yang at intel.com>
> >
> > Is this fix needed for 4.1, or it's only for 4.2?
> 
> It's a bug fix, and as such should go to all kernels, even with cc to 
> stable. That said, it mainly concerns Skylake, so kernels that don't 
> support Skylake would not need a backport.

The patch can't be applied even to 4.1 as is because of the code
structure change.  So, Cc to stable doesn't work, in anyway.

> > I vaguely remember of a bug report.  If there is any relevant bug
> > report, please give the link, too.
> 
> I think this was raised to Intel by us. The use case is when the 
> integrated GPU is disabled and a discrete GPU is used. In this case the 
> i915 module fails to load. If then the HDMI and analog codec are both on 
> the same controller, the entire controller fails instead of just the 
> HDMI codec.
> 
> I'll see if I can get the patch tested ASAP.

OK, the bug seems needed for 4.1 and earlier.  But Libin's patch is
only for 4.2.  And even worse, backporting this isn't
straightforward due to the lack of need_i915_power field.  Hmm.

I think we can make it easier by just allowing to continue the probe.
A totally untested patch for 4.1 is below.


thanks,

Takashi

---
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index fea198c58196..3903a62ce1e8 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -340,6 +340,11 @@ enum {
 #define use_vga_switcheroo(chip)	0
 #endif
 
+#define CONTROLLER_IN_GPU(pci) (((pci)->device == 0x0a0c) || \
+					((pci)->device == 0x0c0c) || \
+					((pci)->device == 0x0d0c) || \
+					((pci)->device == 0x160c))
+
 static char *driver_short_names[] = {
 	[AZX_DRIVER_ICH] = "HDA Intel",
 	[AZX_DRIVER_PCH] = "HDA Intel PCH",
@@ -1854,8 +1859,12 @@ static int azx_probe_continue(struct azx *chip)
 	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL) {
 #ifdef CONFIG_SND_HDA_I915
 		err = hda_i915_init(hda);
-		if (err < 0)
-			goto out_free;
+		if (err < 0) {
+			if (CONTROLLER_IN_GPU(pci))
+				goto out_free;
+			else
+				goto skip_i915;
+		}
 		err = hda_display_power(hda, true);
 		if (err < 0) {
 			dev_err(chip->card->dev,
@@ -1865,6 +1874,7 @@ static int azx_probe_continue(struct azx *chip)
 #endif
 	}
 
+ skip_i915:
 	err = azx_first_init(chip);
 	if (err < 0)
 		goto out_free;