Re: [PATCH] drm/i915/audio: do not set Maud/Naud values manually on KBL

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>-----Original Message-----
>From: Intel-gfx [mailto:intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of
>Rodrigo Vivi
>Sent: Wednesday, February 7, 2018 2:35 AM
>To: Nikula, Jani <jani.nikula@xxxxxxxxx>
>Cc: Zhang, Keqiao <keqiao.zhang@xxxxxxxxx>; Liu, Alice <alice.liu@xxxxxxxxx>;
>intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Cui, YuepingX <yuepingx.cui@xxxxxxxxx>; # v4 .
>10+ <stable@xxxxxxxxxxxxxxx>; Wang Zhijun <zhijunx.wang@xxxxxxxxx>; Libin
>Yang <libin.yang@xxxxxxxxxxxxxxx>
>Subject: Re:  [PATCH] drm/i915/audio: do not set Maud/Naud values
>manually on KBL
>
>On Tue, Feb 06, 2018 at 11:49:18AM +0000, Jani Nikula wrote:
>> Apparently using the manual Maud/Naud mode does not work on KBL. The
>> details on the failure mode are scarce, except that there's no audio,
>> and there is obviously no idea on the root cause either. It is also
>> unknown whether the failure can be reproduced on newer platforms in
>> some scenarios.
>>
>> The problem was introduced when switching from automatic mode to
>> manual mode in commit 6014ac122ed0 ("drm/i915/audio: set proper N/M
>in
>> modeset"). Instead of reverting that, disable the feature on KBL as a
>> workaround.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104093
>> Reported-by: Quanxian Wang <quanxian.wang@xxxxxxxxx>
>> Fixes: 6014ac122ed0 ("drm/i915/audio: set proper N/M in modeset")
>> Cc: <stable@xxxxxxxxxxxxxxx> # v4.10+
>> Cc: Keqiao Zhang <keqiao.zhang@xxxxxxxxx>
>> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>> Cc: Mengdong Lin <mengdong.lin@xxxxxxxxx>
>> Cc: Libin Yang <libin.yang@xxxxxxxxxxxxxxx>
>> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
>> Cc: Quanxian Wang <quanxian.wang@xxxxxxxxx>
>> Cc: Wang Zhijun <zhijunx.wang@xxxxxxxxx>
>> Cc: Cui Yueping <yuepingx.cui@xxxxxxxxx>
>> Cc: Alice Liu <alice.liu@xxxxxxxxx>
>> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
>> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
>>
>> ---
>>
>> UNTESTED. Please provide Tested-by's on the affected KBLs, but *also*
>> on CFL, CNL, etc.
>> ---
>>  drivers/gpu/drm/i915/intel_audio.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_audio.c
>> b/drivers/gpu/drm/i915/intel_audio.c
>> index 522d54fecb53..b7634cff12b6 100644
>> --- a/drivers/gpu/drm/i915/intel_audio.c
>> +++ b/drivers/gpu/drm/i915/intel_audio.c
>> @@ -294,12 +294,19 @@ hsw_dp_audio_config_update(struct
>intel_encoder *encoder,
>>  	struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
>>  	enum port port = encoder->port;
>>  	enum pipe pipe = crtc->pipe;
>> -	const struct dp_aud_n_m *nm;
>> +	const struct dp_aud_n_m *nm = NULL;
>>  	int rate;
>>  	u32 tmp;
>>
>>  	rate = acomp ? acomp->aud_sample_rate[port] : 0;
>> -	nm = audio_config_dp_get_n_m(crtc_state, rate);
>> +
>> +	/*
>> +	 * FIXME: For reasons still unknown, there seem to be issues with the
>> +	 * manual Maud/Naud mode on KBL.
>> +	 */
>> +	if (!IS_KABYLAKE(dev_priv))
>
>Hmm... not much visibility on the audio gap between KBL and CFL.
>But on our side I believe we should also apply it for CFL.
>
>I wonder if some bugs audio guys are hunting now on CNL and ICL could also
>be related to it.

I'm wondering whether the later new platforms will have the same
behavior with KBL. If it is true, maybe we should use
+  if (need_manual_nm())

Let wait and see the later platforms behavior.

Regards,
Libin

>
>Isn't revert the original an option?
>
>> +		nm = audio_config_dp_get_n_m(crtc_state, rate);
>> +
>>  	if (nm)
>>  		DRM_DEBUG_KMS("using Maud %u, Naud %u\n", nm->m,
>nm->n);
>>  	else
>> --
>> 2.11.0
>>
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