lkml.org 
[lkml]   [2017]   [Dec]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [alsa-devel] [PATCH v4 09/15] soundwire: Add slave status handling
From
Date
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.

\
 
 \ /
  Last update: 2017-12-04 04:11    [W:0.262 / U:0.644 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site