linux-kernel - Re: [PATCH v4 1/2] Partially revert ASoC: qcom: Fix enabling BCLK and LRCLK in LPAIF invalid state

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Message-ID: <89456f01-aa02-7a7d-a47b-bf1f26e66d4c@codeaurora.org>
Date:   Mon, 14 Dec 2020 18:13:22 +0530
From:   Srinivasa Rao Mandadapu <srivasam@...eaurora.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org, lgirdwood@...il.com,
        robh+dt@...nel.org, plai@...eaurora.org, bgoswami@...eaurora.org,
        perex@...ex.cz, tiwai@...e.com, srinivas.kandagatla@...aro.org,
        rohitkr@...eaurora.org, linux-arm-msm@...r.kernel.org,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        V Sujith Kumar Reddy <vsujithk@...eaurora.org>
Subject: Re: [PATCH v4 1/2] Partially revert ASoC: qcom: Fix enabling BCLK and
 LRCLK in LPAIF invalid state

Thanks Mark for Your time!!!

On 12/1/2020 11:21 PM, Mark Brown wrote:
> On Tue, Dec 01, 2020 at 11:01:21PM +0530, Srinivasa Rao Mandadapu wrote:
>> On 11/30/2020 6:16 PM, Mark Brown wrote:
>>> Part of this commit message says that the problem was making the registers
>>> non-volatile but both the change and the rest of the commit message say
>>> that the issue was that the registers were made volatile.  I'm also
>>> still unclear as to what the issue is either way - how does reading the
>>> state of the registers from the hardware instead of the cache affect
>>> things?
>> Initial problem was, during playback if device suspended, I2S and DMA
>> control registers
>> are getting reset and unable to recover playback after resume.
>> As these registers were non volatile registers, driver is not getting actual
>> register value
>> and unable to report error state to application. Due to this application
>> keeps on polling for HW current pointer state and not exited from PCM
>> running state.
>> Later from review comments by Srinivas kandagatla, I got to know
>>
>> about regcache sync APIs, which can be used  to sync cache after resume and
>>
>> HW registers can be updated with  original values. With that playback can be
>> continued.
>>
>> So is the reason, I am reverting partial changes in the commit b1824968221c.
> I don't understand why a fix for the register cache not being in sync
> with the hardware doesn't involve syncing the register cache with the
> hardware.

I am sorry I couldn't understand your point. Could you please elaborate 
your query?

Actually I posted V5 version based on review comments.

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