linux-kernel - Re: [PATCH 2/6] ASoC: amd: yc: Add a module parameter to influence pdm

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Message-ID: <e9733e9a-ac70-846f-c3a2-f96a6787b9bc@perex.cz>
Date:   Fri, 27 Jan 2023 17:41:44 +0100
From:   Jaroslav Kysela <perex@...ex.cz>
To:     "Limonciello, Mario" <Mario.Limonciello@....com>,
        "Mukunda, Vijendar" <Vijendar.Mukunda@....com>,
        "Saba Kareem, Syed" <Syed.SabaKareem@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "Pananchikkal, Renjith" <Renjith.Pananchikkal@....com>,
        Mark Pearson <mpearson@...ovo.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>
Subject: Re: [PATCH 2/6] ASoC: amd: yc: Add a module parameter to influence
 pdm_gain

On 27. 01. 23 17:25, Limonciello, Mario wrote:
> [AMD Official Use Only - General]
> 
> 
> 
>> -----Original Message-----
>> From: Jaroslav Kysela <perex@...ex.cz>
>> Sent: Friday, January 27, 2023 10:23
>> To: Limonciello, Mario <Mario.Limonciello@....com>; Mukunda, Vijendar
>> <Vijendar.Mukunda@....com>; Saba Kareem, Syed
>> <Syed.SabaKareem@....com>; linux-kernel@...r.kernel.org
>> Cc: Pananchikkal, Renjith <Renjith.Pananchikkal@....com>; Mark Pearson
>> <mpearson@...ovo.com>; Liam Girdwood <lgirdwood@...il.com>; Mark
>> Brown <broonie@...nel.org>; Takashi Iwai <tiwai@...e.com>; alsa-
>> devel@...a-project.org
>> Subject: Re: [PATCH 2/6] ASoC: amd: yc: Add a module parameter to
>> influence pdm_gain
>>
>> On 27. 01. 23 17:01, Mario Limonciello wrote:
>>> In case of regressions for any users that the new pdm_gain value is
>>> too high and for additional debugging, introduce a module parameter
>>> that would let them configure it.
>>>
>>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>>> ---
>>>    sound/soc/amd/yc/acp6x-pdm-dma.c | 7 ++++++-
>>>    sound/soc/amd/yc/acp6x.h         | 2 +-
>>>    2 files changed, 7 insertions(+), 2 deletions(-)
>>
>> ...
>>
>>>    	pdm_ctrl = acp6x_readl(acp_base + ACP_WOV_MISC_CTRL);
>>> -	pdm_ctrl |= ACP_WOV_MISC_CTRL_MASK;
>>> +	pdm_ctrl |= FIELD_PREP(ACP_WOV_GAIN_CONTROL, pdm_gain);
>>
>> The bits should be zeroed (AND - &) before OR to make sure that the correct
>> value is written to the register. More related patches are affected.
> 
> I had consider this, but the hardware default at reset is 0x0.  Do you think it's
> still necessary for posterity?

You're using 0644 permissions for the module parameter, so the value can be 
changed by root using sysfs anytime (between SNDRV_PCM_TRIGGER calls).

						Jaroslav

-- 
Jaroslav Kysela <perex@...ex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.