[alsa-devel] [PATCH] ALSA: hda - add AZX_DCAPS_I915_POWERWELL to Baytrail

[Takashi Iwai]

At Tue, 21 Apr 2015 11:29:47 +0200,
David Henningsson wrote:
> 
> Hi,
> 
> Baytrail is very much released and out there already - should this patch 
> also go to stable?

I thought of that, but this patch also has a drawback, thus I
hesitated to make it blindly.

> Are there current problems (like HDMI codec not being detected) that are 
> fixed by this patch?

If there is a known bug (report) and this fixes indeed, it deserves
the stable kernel, indeed.


Takashi


> // David
> 
> On 2015-04-21 07:12, mengdong.lin at intel.com wrote:
> > From: Mengdong Lin <mengdong.lin at intel.com>
> >
> > This patch addes AZX_DCAPS_I915_POWERWELL to BYT (Baytrail).
> >
> > Like Braswell and Skylake, the HDMI codec on Bytrail is also in the shared
> > power well with GPU. This power well must be turned on before we reset link
> > to probe the codec, to avoid communication failure with the codec.
> >
> > The side effect is that this power is always ON in S0 because the BYT HDMI
> > codec does not support EPSS or D3ClkStop and so the controller doesn't enter
> > D3 at runtime, and the HDMI codec and analog codec share a single physical
> > HD-A link and so we cannot reset the HD-A link freely when we re-enable the
> > power to use the HDMI codec.
> >
> > Next step is to test if an AGP reset or double AGP reset on BYT HDMI codec is
> > okay to bring the HDMI codec back to a functional state after restoring the
> > power. If okay, we can bind the power on/off with the HDMI codec PM without
> > interrupting the analog audio.
> >
> > Signed-off-by: Mengdong Lin <mengdong.lin at intel.com>
> >
> > diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> > index e1c2105..34040d2 100644
> > --- a/sound/pci/hda/hda_intel.c
> > +++ b/sound/pci/hda/hda_intel.c
> > @@ -297,6 +297,9 @@ enum {
> >   	 AZX_DCAPS_PM_RUNTIME | AZX_DCAPS_I915_POWERWELL |\
> >   	 AZX_DCAPS_SNOOP_TYPE(SCH))
> >
> > +#define AZX_DCAPS_INTEL_BAYTRAIL \
> > +	(AZX_DCAPS_INTEL_PCH_NOPM | AZX_DCAPS_I915_POWERWELL)
> > +
> >   #define AZX_DCAPS_INTEL_BRASWELL \
> >   	(AZX_DCAPS_INTEL_PCH | AZX_DCAPS_I915_POWERWELL)
> >
> > @@ -1992,7 +1995,7 @@ static const struct pci_device_id azx_ids[] = {
> >   	  .driver_data = AZX_DRIVER_SCH | AZX_DCAPS_INTEL_PCH_NOPM },
> >   	/* BayTrail */
> >   	{ PCI_DEVICE(0x8086, 0x0f04),
> > -	  .driver_data = AZX_DRIVER_PCH | AZX_DCAPS_INTEL_PCH_NOPM },
> > +	  .driver_data = AZX_DRIVER_PCH | AZX_DCAPS_INTEL_BAYTRAIL },
> >   	/* Braswell */
> >   	{ PCI_DEVICE(0x8086, 0x2284),
> >   	  .driver_data = AZX_DRIVER_PCH | AZX_DCAPS_INTEL_BRASWELL },
> >
> 
> -- 
> David Henningsson, Canonical Ltd.
> https://launchpad.net/~diwic
>