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SubjectRe: [alsa-devel] [PATCH v4 09/15] soundwire: Add slave status handling
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On 12/3/17 11:11 AM, Vinod Koul wrote:
> On Fri, Dec 01, 2017 at 05:52:03PM -0600, Pierre-Louis Bossart wrote:
>
>>> + status = sdw_read(slave, SDW_DP0_INT);
>>> + if (status < 0) {
>>> + dev_err(slave->bus->dev,
>>> + "SDW_DP0_INT read failed:%d", status);
>>> + return status;
>>> + }
>>> +
>>> + count++;
>>> +
>>> + /* we can get alerts while processing so keep retrying */
>>
>> This is not incorrect, but this goes beyond what the spec requires.
>>
>> The additional read is to make sure some interrupts are not lost due to a
>> known race condition. It would be enough to mask the status read the second
>> time to only check if the interrupts sources which were cleared are still
>> signaling something.
>>
>> With the code as it is, you may catch *new* interrupt sources, which could
>> impact the arbitration/priority/policy in handling interrupts. It's not
>> necessarily bad, but you'd need to document whether you want to deal with
>> the race condition described in the MIPI spec or try to be smarter.
>
> This was based on your last comment, lets discuss more offline on this to
> see what else is required here.
>

I am fine if you leave the code as is for now, it's not bad but can be
optimized.

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