[alsa-devel] [PATCH] ALSA: hda - Force to link down at runtime suspend on ATI/AMD HDMI

[Takashi Iwai]

Henning Kühn reported that the discrete AMD GPU on his hybrid graphics
laptop no longer runtime-suspends due to the recent commit
07f4f97d7b4b ("vga_switcheroo: Use device link for HDA controller").

The root cause is that the HDMI codec on AMD GPU doesn't support
CLKSTOP and EPSS, which are currently mandatory for powering down the
HD-audio link at runtime suspend.  Because the HD-audio link is still
up, HD-audio controller driver blocks the transition to D3.

For addressing the regression, this patch adds a new flag to indicate
the forced link-down, and sets it for AMD HDMI codecs appropriately
in the codec driver.

Fixes: 07f4f97d7b4b ("vga_switcheroo: Use device link for HDA controller")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106957
Reported-by: Lukas Wunner <lukas at wunner.de>
Reported-and-tested-by: Henning Kühn <prg at cooco.de>
Cc: <stable at vger.kernel.org> # v4.17+
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/pci/hda/hda_codec.c  | 5 +++--
 sound/pci/hda/hda_codec.h  | 1 +
 sound/pci/hda/patch_hdmi.c | 5 +++++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
index d91c87e41756..20a171ac4bb2 100644
--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -2899,8 +2899,9 @@ static int hda_codec_runtime_suspend(struct device *dev)
 	list_for_each_entry(pcm, &codec->pcm_list_head, list)
 		snd_pcm_suspend_all(pcm->pcm);
 	state = hda_call_codec_suspend(codec);
-	if (codec_has_clkstop(codec) && codec_has_epss(codec) &&
-	    (state & AC_PWRST_CLK_STOP_OK))
+	if (codec->link_down_at_suspend ||
+	    (codec_has_clkstop(codec) && codec_has_epss(codec) &&
+	     (state & AC_PWRST_CLK_STOP_OK)))
 		snd_hdac_codec_link_down(&codec->core);
 	snd_hdac_link_power(&codec->core, false);
 	return 0;
diff --git a/sound/pci/hda/hda_codec.h b/sound/pci/hda/hda_codec.h
index 681c360f29f9..a8b1b31f161c 100644
--- a/sound/pci/hda/hda_codec.h
+++ b/sound/pci/hda/hda_codec.h
@@ -258,6 +258,7 @@ struct hda_codec {
 	unsigned int power_save_node:1; /* advanced PM for each widget */
 	unsigned int auto_runtime_pm:1; /* enable automatic codec runtime pm */
 	unsigned int force_pin_prefix:1; /* Add location prefix */
+	unsigned int link_down_at_suspend:1; /* link down at runtime suspend */
 #ifdef CONFIG_PM
 	unsigned long power_on_acct;
 	unsigned long power_off_acct;
diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index 8840daf9c6a3..98e1c411c56a 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -3741,6 +3741,11 @@ static int patch_atihdmi(struct hda_codec *codec)
 
 	spec->chmap.channels_max = max(spec->chmap.channels_max, 8u);
 
+	/* AMD GPUs have neither EPSS nor CLKSTOP bits, hence preventing
+	 * the link-down as is.  Tell the core to allow it.
+	 */
+	codec->link_down_at_suspend = 1;
+
 	return 0;
 }
 
-- 
2.17.1