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Date:   Fri, 1 May 2020 01:38:16 +0800
From:   Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
To:     Takashi Iwai <tiwai@suse.de>
Cc:     Alex Deucher <alexdeucher@gmail.com>,
        "Zhou, David(ChunMing)" <David1.Zhou@amd.com>,
        "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
        Takashi Iwai <tiwai@suse.com>, Lukas Wunner <lukas@wunner.de>,
        "Deucher, Alexander" <Alexander.Deucher@amd.com>,
        "Koenig, Christian" <Christian.Koenig@amd.com>
Subject: Re: [PATCH 0/1] Fiji GPU audio register timeout when in BACO state
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On Thu, Apr 30, 2020 at 07:01:08PM +0200, Takashi Iwai wrote:
> On Thu, 30 Apr 2020 18:52:20 +0200,
> Nicholas Johnson wrote:
> > 
> > On Thu, Apr 30, 2020 at 05:14:56PM +0200, Takashi Iwai wrote:
> > > On Wed, 29 Apr 2020 18:19:57 +0200,
> > > Alex Deucher wrote:
> > > > 
> > > > On Wed, Apr 29, 2020 at 12:05 PM Takashi Iwai <tiwai@suse.de> wrote:
> > > > > Well, but the code path there is the runtime PM resume of the audio
> > > > > device and it means that GPU must have been runtime-resumed again
> > > > > beforehand via the device link.  So, it should have worked from the
> > > > > beginning but in reality not -- that is, apparently some inconsistency
> > > > > is found in the initial attempt of the runtime resume...
> > > > 
> > > > Yeah, it should be covered, but I wonder if there is something in the
> > > > ELD update sequence that needs to call pm_runtime_get_sync()?  The ELD
> > > > sequence on AMD GPUs doesn't work the same as on other vendors.  The
> > > > GPU driver has a backdoor into the HDA device's verbs to set update
> > > > the audio state rather than doing it via an ELD buffer update.  We
> > > > still update the ELD buffer for consistency.  Maybe when the GPU
> > > > driver sets the audio state at monitor detection time that triggers an
> > > > interrupt or something on the HDA side which races with the CPU and
> > > > the power down of the GPU.  That still seems unlikely though since the
> > > > runtime pm on the GPU side defaults to a 5 second suspend timer.
> > > 
> > > I'm not sure whether it's the race between runtime suspend of GPU vs
> > > runtime resume of audio.  My wild guess is rather that it's the timing
> > > GPU notifies to the audio; then the audio driver notifies to
> > > user-space and user-space opens the stream, which in turn invokes the
> > > runtime resume of GPU. But in GPU side, it's still under processing,
> > > so it proceeds before the GPU finishes its initialization job.
> > > 
> > > Nicholas, could you try the patch below and see whether the problem
> > > still appears?  The patch artificially delays the notification and ELD
> > > update for 300msec.  If this works, it means the timing problem.
> > The bug still occurred after applying the patch.
> > 
> > But you were absolutely correct - it just needed to be increased to 
> > 3000ms - then the bug stopped.
> 
> Interesting.  3 seconds are too long, but I guess 1 second would work
> as well?
1000ms indeed worked as well.

> 
> In anyway, the success with a long delay means that the sound setup
> after the full runtime resume of GPU seems working.
> 
> > Now the question is, what do we do now that we know this?
> > 
> > Also, are you still interested in the contents of the ELD# files? I can 
> > dump them all into a file at some specific moment in time which you 
> > request, if needed.
> 
> Yes, please take the snapshot before plugging, right after plugging
> and right after enabling.  I'm not sure whether your monitor supports
> the audio, and ELD contents should show that, at least.
The monitor supports the audio. There is 3.5mm audio out jack. No 
inbuilt speakers, although Samsung did sell a sound bar to suit it. The 
sound bar, which I do not own, presumably attaches via 3.5mm jack.

I am not sure if by plugging, you mean hot-adding Thunderbolt GPU or 
plugging the monitor to the GPU, so I have covered extra cases to be 
sure. I have taken the eld# files with the 1000ms patch applied, so the 
error is not triggered.

####
Before hot-adding the Thunderbolt GPU:
/proc/asound/card1 not present
####
####
After hot-adding the GPU with no monitor attached:

/proc/asound/card1 contains:
eld#0.0  eld#0.1  eld#0.2  eld#0.3  eld#0.4  eld#0.5

All of the above have the same contents:

monitor_present         0
eld_valid               0
####
####
Monitor attached to Fiji GPU but not enabled:

Same as above
####
####
Monitor enabled:

All files with same contents except for eld#0.1 which looks like:

monitor_present         1
eld_valid               1
monitor_name            U32E850
connection_type         DisplayPort
eld_version             [0x2] CEA-861D or below
edid_version            [0x3] CEA-861-B, C or D
manufacture_id          0x2d4c
product_id              0xce3
port_id                 0x0
support_hdcp            0
support_ai              0
audio_sync_delay        0
speakers                [0x1] FL/FR
sad_count               1
sad0_coding_type        [0x1] LPCM
sad0_channels           2
sad0_rates              [0xe0] 32000 44100 48000
sad0_bits               [0xe0000] 16 20 24
####

Cheers.
Regards, Nicholas.

> 
> 
> thanks,
> 
> Takashi