linux-kernel - Re: [PATCH v2] soundwire: qcom: remove redundant wait for completion

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Message-ID: <90408caa-6b3b-bd09-10ca-bc6c4431111f@quicinc.com>
Date:   Sat, 26 Feb 2022 18:19:53 +0530
From:   Srinivasa Rao Mandadapu <quic_srivasam@...cinc.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        <agross@...nel.org>, <bjorn.andersson@...aro.org>,
        <lgirdwood@...il.com>, <broonie@...nel.org>, <robh+dt@...nel.org>,
        <quic_plai@...cinc.com>, <bgoswami@...eaurora.org>,
        <perex@...ex.cz>, <tiwai@...e.com>, <rohitkr@...eaurora.org>,
        <linux-arm-msm@...r.kernel.org>, <alsa-devel@...a-project.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <swboyd@...omium.org>, <judyhsiao@...omium.org>,
        <yung-chuan.liao@...ux.intel.com>, <sanyog.r.kale@...el.com>
CC:     Venkata Prasad Potturu <quic_potturu@...cinc.com>
Subject: Re: [PATCH v2] soundwire: qcom: remove redundant wait for completion


On 2/25/2022 11:33 PM, Srinivas Kandagatla wrote:
Thanks for Your time Srini!!!
>
> On 25/02/2022 15:43, Pierre-Louis Bossart wrote:
>>
>>
>> On 2/25/22 08:45, Srinivas Kandagatla wrote:
>>>
>>>
>>> On 25/02/2022 14:44, Srinivasa Rao Mandadapu wrote:
>>>> Remove wait_for_completion_timeout from soundwire probe as it seems
>>>> unnecessary and device enumeration is anyway not happening here,
>>>> hence this api is blocking till it completes max wait time.
>>>> Also, as device enumeration event is dependent on wcd938x probe to be
>>>> completed, its of no use waiting here.
>>>> Waiting here increasing the boot time almost 4 seconds and impacting
>>>> other modules like touch screen.
>>>>
>>>> Fixes: 06dd96738d618 ("soundwire: qcom: wait for enumeration to be
>>>> complete in probe")
>>>>
>>>> Signed-off-by: Srinivasa Rao Mandadapu <quic_srivasam@...cinc.com>
>>>> Co-developed-by: Venkata Prasad Potturu <quic_potturu@...cinc.com>
>>>> Signed-off-by: Venkata Prasad Potturu <quic_potturu@...cinc.com>
>>>
>>> LGTM,
>>>
>>> Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>>
>> I don't get the idea, sorry.
>>
>> If you look at the code, these are the cases where this 'struct
>> completion' is used
>>
>>     struct completion enumeration;
>>     complete(&ctrl->enumeration);
>>     /* Enable Auto enumeration */
>>     init_completion(&ctrl->enumeration);
>>     wait_for_completion_timeout(&ctrl->enumeration,
>>
>>
>> so if you remove the wait_for_completeion, then you might just as well
>> remove the whole thing and revert 06dd96738d618
>>
>> what am I missing?
> Yes, that makes more sense to revert it, as it is the only user of 
> this completion.
> We could add it back when we really need this again in pm runtime 
> setup if required.
>
> --srini
Thanks for confirmation. Sent revert patch.
>>
>>
>>>> ---
>>>>    drivers/soundwire/qcom.c | 2 --
>>>>    1 file changed, 2 deletions(-)
>>>>
>>>> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
>>>> index 5481341..9a32a24 100644
>>>> --- a/drivers/soundwire/qcom.c
>>>> +++ b/drivers/soundwire/qcom.c
>>>> @@ -1309,8 +1309,6 @@ static int qcom_swrm_probe(struct
>>>> platform_device *pdev)
>>>>        }
>>>>          qcom_swrm_init(ctrl);
>>>> -    wait_for_completion_timeout(&ctrl->enumeration,
>>>> -                    msecs_to_jiffies(TIMEOUT_MS));
>>>>        ret = qcom_swrm_register_dais(ctrl);
>>>>        if (ret)
>>>>            goto err_master_add;