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References: <20210524142114.18676-1-srivasam@codeaurora.org>
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From:   Doug Anderson <dianders@chromium.org>
Date:   Tue, 1 Jun 2021 08:17:06 -0700
Message-ID: <CAD=FV=X+3qP3uj2AVkejmVBmMYqWAxMCS7HBRSkKcPgwP0XGdQ@mail.gmail.com>
Subject: Re: [PATCH v3] ASoC: qcom: lpass-cpu: Fix pop noise during audio
 capture begin
To:     Srinivasa Rao Mandadapu <srivasam@codeaurora.org>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Patrick Lai <plai@codeaurora.org>,
        Banajit Goswami <bgoswami@codeaurora.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Rohit kumar <rohitkr@codeaurora.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        ALSA Development Mailing List <alsa-devel@alsa-project.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Judy Hsiao <judyhsiao@chromium.org>
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Precedence: bulk

Hi,

On Mon, May 24, 2021 at 7:21 AM Srinivasa Rao Mandadapu
<srivasam@codeaurora.org> wrote:
>
> This patch fixes PoP noise of around 15ms observed during audio capture begin.
> Enables BCLK and LRCLK in snd_soc_dai_ops prepare call for introducing some delay
> before capture start and clock enable.
>
> Co-developed-by: Judy Hsiao <judyhsiao@chromium.org>
> Signed-off-by: Judy Hsiao <judyhsiao@chromium.org>
> Signed-off-by: Srinivasa Rao Mandadapu <srivasam@codeaurora.org>
> ---
> Changes Since V2:
>         -- Updated comments as per linux style
>         -- Removed unrelated changes.
> Changes Since V1:
>         -- Enableed BCLK and LRCLK in dai ops prepare API instead of startup API
>         -- Added comments
>
>  sound/soc/qcom/lpass-cpu.c | 54 +++++++++++++++++++++++++++++++++++++-
>  1 file changed, 53 insertions(+), 1 deletion(-)

Presumably related with Srinivas Kandagatla's comments: this patch
causes a bad splat at bootup. Specifically, here's what I saw when
this patch was in the Chrome OS 5.4 kernel:

------------[ cut here ]------------
lpass_audio_core_lpaif_pri_ibit_clk already disabled
WARNING: CPU: 0 PID: 2066 at drivers/clk/clk.c:958 clk_core_disable+0x4a0/0x670
CPU: 0 PID: 2066 Comm: cras Not tainted 5.4.122-lockdep #4
Hardware name: Google Lazor (rev1 - 2) with LTE (DT)
pstate: 60400089 (nZCv daIf +PAN -UAO)
pc : clk_core_disable+0x4a0/0x670
lr : clk_core_disable+0x4a0/0x670
sp : ffffff81727cf8a0
x29: ffffff81727cf8a0 x28: 1ffffff033d2b8d5
x27: dfffffd000000000 x26: ffffff81a3781980
x25: 1ffffff03493d3b3 x24: ffffff816f433480
x23: dfffffd000000000 x22: 1ffffff035b66e2f
x21: 00000000ffffffff x20: ffffff81adb3717c
x19: ffffff81adb37100 x18: 0000000000000339
x17: ffffffffffffffff x16: 0000000000000006
x15: 0000000000000001 x14: 0720072007200720
x13: 0000000000000000 x12: ffffffd0132c1e00
x11: 0000000000000001 x10: 0000000000000000
x9 : cff2cb5e2cb22e00 x8 : cff2cb5e2cb22e00
x7 : ffffffd010288f74 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001
x3 : ffffffd010429d10 x2 : 0000000000000001
x1 : 0000000000000008 x0 : 0000000000000034
Call trace:
 clk_core_disable+0x4a0/0x670
 clk_disable+0x50/0x64
 lpass_cpu_daiops_shutdown+0x190/0x204 [snd_soc_lpass_cpu]
 snd_soc_dai_shutdown+0x8c/0x9c
 soc_pcm_close+0x258/0x478
 snd_pcm_release_substream+0xfc/0x1e8
 snd_pcm_release+0x8c/0x124
 __fput+0x1e4/0x4fc
 ____fput+0x1c/0x28
 task_work_run+0x12c/0x164
 do_notify_resume+0x1e04/0x2c48
 work_pending+0x8/0x14
irq event stamp: 101552

-Doug