On Wed, Jun 20, 2018 at 12:14:32PM +0200, Takashi Iwai wrote:
On Wed, 20 Jun 2018 11:34:52 +0200, Lukas Wunner wrote:
Henning Kühn reports that due to my commit 07f4f97d7b4b ("vga_switcheroo: Use device link for HDA controller"), the discrete GPU on his hybrid graphics laptop no longer runtime suspends.
The root cause is that the single codec of the GPU's HDA controller doesn't support CLKSTOP and EPSS. (The "Supported Power States" are 0x00000009, i.e. CLKSTOP and EPSS bits are not set, cf. page 209 of the HDA spec.)
This means that in hda_codec_runtime_suspend() we do not call snd_hdac_codec_link_down():
if (codec_has_clkstop(codec) && codec_has_epss(codec) && (state & AC_PWRST_CLK_STOP_OK)) snd_hdac_codec_link_down(&codec->core);
If snd_hdac_codec_link_down() isn't called, the bit in the codec_powered bitmask isn't cleared, which in turn prevents the controller from going to PCI_D3hot in azx_runtime_idle():
if (!power_save_controller || !azx_has_pm_runtime(chip) || azx_bus(chip)->codec_powered || !chip->running) return -EBUSY;
The codec does runtime suspend to D3, but the PS-ClkStopOk bit in the response to "Get Power State" is not set. (Response is 0x00000033, cf. page 151 of the HD Audio spec.) Hence the check above "state & AC_PWRST_CLK_STOP_OK" also results in "false".
Supposing that it's AMD GPU, does a fix like below work?
[snip]
--- 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;
}
In hda_intel.c:azx_probe_continue(), we currently do this:
if (use_vga_switcheroo(hda)) list_for_each_codec(codec, &chip->bus) codec->auto_runtime_pm = 1;
An alternative to setting the flag in patch_atihdmi() would be to set it here.
One small nit, the code comment you're adding above is in network subsystem style ("/*" isn't on a line by itself).
Otherwise this is Reviewed-by: Lukas Wunner lukas@wunner.de Reported-and-tested-by: Henning Kühn prg@cooco.de Fixes: 07f4f97d7b4b ("vga_switcheroo: Use device link for HDA controller") Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106957
Feel free to just copy/paste the problem description from my original e-mail to the commit message so that you don't have additional work there.
Thanks so much for the fast response with a working patch!
Lukas