[Intel-gfx] [PATCH] drm/i915: Acquire audio powerwell for HD-Audio registers

[Hans de Goede]

Hi,

On 04-08-16 23:03, Takashi Iwai wrote:
> [dropped stable ML and add a few other relevant people to Cc]
>
> On Thu, 04 Aug 2016 20:05:27 +0200,
> Takashi Iwai wrote:
>>
>> On Thu, 04 Aug 2016 18:44:11 +0200,
>> Daniel Vetter wrote:
>>>
>>> On Wed, Aug 03, 2016 at 05:09:00PM +0100, Chris Wilson wrote:
>>>> On Haswell/Broadwell, the HD-Audio block is inside the HDMI/display
>>>> power well and so the sna-hda audio codec acquires the display power
>>>> well while it is operational. However, Skylake separates the powerwells
>>>> again, but yet we still need the audio powerwell to setup the registers.
>>>> (But then the hardware uses those registers even while powered off???)
>>>
>>> Yeah feels fishy, but will at least duct-tape over the breakage from the
>>> audio side. Most likely the reg writes go exactly nowhere and there's a
>>> bug on the audio side. And this patch doesn't fix that.
>>
>> Well, if the relevant code paths are only over these callbacks, I
>> guess the following fix would work instead.
>>
>> Can anyone check?
>
> Scratch the previous one.  There is another place calling similarly.
>
> Now looking back at the code again, I believe that the better way
> would be to properly do power up / down at the resume callbacks.
>
> Below is an untested patch.  Let me know if this actually works.

I've build a 4.7 kernel with this patch and I can confirm that it
fixes the WARN_ON I was seeing in my XPS 9550 without this patch.

Thanks & Regards,

Hans



> thanks,
>
> Takashi
>
> -- 8< --
> From: Takashi Iwai <tiwai at suse.de>
> Subject: [PATCH] ALSA: hda - Manage power well properly for resume
>
> For SKL and later Intel chips, we control the power well per codec
> basis via link_power callback since the commit [03b135cebc47: ALSA:
> hda - remove dependency on i915 power well for SKL].
> However, there are a few exceptional cases where the gfx registers are
> accessed from the audio driver: namely the wakeup override bit
> toggling at (both system and runtime) resume.  This seems causing a
> kernel warning when accessed during the power well down (and likely
> resulting in the bogus register accesses).
>
> This patch puts the proper power up / down sequence around the resume
> code so that the wakeup bit is fiddled properly while the power is
> up.  (The other callback, sync_audio_rate, is used only in the PCM
> callback, so it's guaranteed in the power-on.)
>
> Also, by this proper power up/down, the instantaneous flip of wakeup
> bit in the resume callback that was introduced by the commit
> [033ea349a7cd: ALSA: hda - Fix Skylake codec timeout] becomes
> superfluous, as snd_hdac_display_power() already does it.  So we can
> clean it up together.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96214
> Fixes: 03b135cebc47 ('ALSA: hda - remove dependency on i915 power well for SKL')
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
>  sound/pci/hda/hda_intel.c | 32 ++++++++++++++++++++------------
>  1 file changed, 20 insertions(+), 12 deletions(-)
>
> diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> index 89dacf9b4e6c..160c7f713722 100644
> --- a/sound/pci/hda/hda_intel.c
> +++ b/sound/pci/hda/hda_intel.c
> @@ -906,20 +906,23 @@ static int azx_resume(struct device *dev)
>  	struct snd_card *card = dev_get_drvdata(dev);
>  	struct azx *chip;
>  	struct hda_intel *hda;
> +	struct hdac_bus *bus;
>
>  	if (!card)
>  		return 0;
>
>  	chip = card->private_data;
>  	hda = container_of(chip, struct hda_intel, chip);
> +	bus = azx_bus(chip);
>  	if (chip->disabled || hda->init_failed || !chip->running)
>  		return 0;
>
> -	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL
> -		&& hda->need_i915_power) {
> -		snd_hdac_display_power(azx_bus(chip), true);
> -		snd_hdac_i915_set_bclk(azx_bus(chip));
> +	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL) {
> +		snd_hdac_display_power(bus, true);
> +		if (hda->need_i915_power)
> +			snd_hdac_i915_set_bclk(bus);
>  	}
> +
>  	if (chip->msi)
>  		if (pci_enable_msi(pci) < 0)
>  			chip->msi = 0;
> @@ -929,6 +932,11 @@ static int azx_resume(struct device *dev)
>
>  	hda_intel_init_chip(chip, true);
>
> +	/* power down again for link-controlled chips */
> +	if ((chip->driver_caps & AZX_DCAPS_I915_POWERWELL) &&
> +	    !hda->need_i915_power)
> +		snd_hdac_display_power(bus, false);
> +
>  	snd_power_change_state(card, SNDRV_CTL_POWER_D0);
>
>  	trace_azx_resume(chip);
> @@ -1008,6 +1016,7 @@ static int azx_runtime_resume(struct device *dev)
>
>  	chip = card->private_data;
>  	hda = container_of(chip, struct hda_intel, chip);
> +	bus = azx_bus(chip);
>  	if (chip->disabled || hda->init_failed)
>  		return 0;
>
> @@ -1015,15 +1024,9 @@ static int azx_runtime_resume(struct device *dev)
>  		return 0;
>
>  	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL) {
> -		bus = azx_bus(chip);
> -		if (hda->need_i915_power) {
> -			snd_hdac_display_power(bus, true);
> +		snd_hdac_display_power(bus, true);
> +		if (hda->need_i915_power)
>  			snd_hdac_i915_set_bclk(bus);
> -		} else {
> -			/* toggle codec wakeup bit for STATESTS read */
> -			snd_hdac_set_codec_wakeup(bus, true);
> -			snd_hdac_set_codec_wakeup(bus, false);
> -		}
>  	}
>
>  	/* Read STATESTS before controller reset */
> @@ -1043,6 +1046,11 @@ static int azx_runtime_resume(struct device *dev)
>  	azx_writew(chip, WAKEEN, azx_readw(chip, WAKEEN) &
>  			~STATESTS_INT_MASK);
>
> +	/* power down again for link-controlled chips */
> +	if ((chip->driver_caps & AZX_DCAPS_I915_POWERWELL) &&
> +	    !hda->need_i915_power)
> +		snd_hdac_display_power(bus, false);
> +
>  	trace_azx_runtime_resume(chip);
>  	return 0;
>  }
>