linux-kernel - Re: [PATCH] ASoC: mediatek: mt8188: Enable apll1 clock during reg rw to prevent hang

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Message-ID: <a70a0521-985d-43a4-a1fa-36eb733d5ca9@collabora.com>
Date: Thu, 5 Dec 2024 13:51:57 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Trevor Wu (吳文良) <Trevor.Wu@...iatek.com>,
 "lgirdwood@...il.com" <lgirdwood@...il.com>,
 "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
 Nicolas Prado <nfraprado@...labora.com>,
 "broonie@...nel.org" <broonie@...nel.org>, "tiwai@...e.com"
 <tiwai@...e.com>, "perex@...ex.cz" <perex@...ex.cz>
Cc: "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "kernel@...labora.com" <kernel@...labora.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-sound@...r.kernel.org" <linux-sound@...r.kernel.org>,
 "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH] ASoC: mediatek: mt8188: Enable apll1 clock during reg rw
 to prevent hang

Il 04/12/24 13:17, Trevor Wu (吳文良) ha scritto:
> On Tue, 2024-12-03 at 17:07 -0300, Nícolas F. R. A. Prado wrote:
> 
>>
>> Currently, booting the Genio 700 EVK board with the MT8188 sound
>> platform driver configured as a module (CONFIG_SND_SOC_MT8188=m)
>> results
>> in a system hang right when the HW registers for the audio controller
>> are read:
>>
>>    mt8188-audio 10b10000.audio-controller: No cache defaults, reading
>> back from HW
>>
>> The hang doesn't occur with the driver configured as builtin as then
>> the
>> unused clocks are still enabled.
>>
>> Enable the apll1 clock during register read/write to prevent the
>> hang.
>>
>> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
>> ---
>>   sound/soc/mediatek/mt8188/mt8188-afe-clk.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/sound/soc/mediatek/mt8188/mt8188-afe-clk.c
>> b/sound/soc/mediatek/mt8188/mt8188-afe-clk.c
>> index
>> e69c1bb2cb239596dee50b166c20192d5408be10..fb8cf286df3f02ac076528b898f
>> d0d7a708ec1ea 100644
>> --- a/sound/soc/mediatek/mt8188/mt8188-afe-clk.c
>> +++ b/sound/soc/mediatek/mt8188/mt8188-afe-clk.c
>> @@ -587,6 +587,8 @@ int mt8188_afe_enable_reg_rw_clk(struct
>> mtk_base_afe *afe)
>>          mt8188_afe_enable_clk(afe, afe_priv-
>>> clk[MT8188_CLK_AUD_A1SYS_HP]);
>>          mt8188_afe_enable_clk(afe, afe_priv-
>>> clk[MT8188_CLK_AUD_A1SYS]);
>>
>> +       mt8188_afe_enable_clk(afe, afe_priv-
>>> clk[MT8188_CLK_APMIXED_APLL1]);
>> +
>>          return 0;
>>   }
> Hi Nicolas,
> 
> If I understand correctly, APLL1 should be the parent clock of
> AUD_A1SYS_HP and AUD_A1SYS, so it should be enabled automatically by
> CCF.
> 
> I'm not sure why you resolved the hang issue after enabling APLL1.
> Could you share more details about the solution?
> 

Hmm. Now I see what's happening here...

Nicolas, Trevor,

Possible parents for top_a1sys_hp are:
  - clk26m
  - apll1_d4

...what's happening here most probably is that after the clock gets disabled as
unused, it gets parented to clk26m by default as that is parent index 0... and
something else in AFE needs APLL1 to feed a clock to .. something .. to allow
register access.

Trevor, do you know why is this IP unaccessible when A1SYS is parented to clk26m?

That might give Nicolas a definitive hint about how to resolve this issue.

Cheers,
Angelo

> Thanks,
> Trevor
> 
>>
>> @@ -594,6 +596,8 @@ int mt8188_afe_disable_reg_rw_clk(struct
>> mtk_base_afe *afe)
>>   {
>>          struct mt8188_afe_private *afe_priv = afe->platform_priv;
>>
>> +       mt8188_afe_disable_clk(afe, afe_priv-
>>> clk[MT8188_CLK_APMIXED_APLL1]);
>> +
>>          mt8188_afe_disable_clk(afe, afe_priv-
>>> clk[MT8188_CLK_AUD_A1SYS]);
>>          mt8188_afe_disable_clk(afe, afe_priv-
>>> clk[MT8188_CLK_AUD_A1SYS_HP]);
>>          mt8188_afe_disable_clk(afe, afe_priv-
>>> clk[MT8188_CLK_AUD_AFE]);
>>
>> ---
>> base-commit: b852e1e7a0389ed6168ef1d38eb0bad71a6b11e8
>> change-id: 20241203-mt8188-afe-fix-hang-disabled-apll1-clk-
>> b3c11782cbaf
>>
>> Best regards,
>> --
>> Nícolas F. R. A. Prado <nfraprado@...labora.com>
>>
>>