[lkml]   [2019]   [Jun]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [alsa-devel] [RFC PATCH 6/6] soundwire: qcom: add support for SoundWire controller

On 11/06/2019 13:21, Pierre-Louis Bossart wrote:
> On 6/11/19 5:29 AM, Srinivas Kandagatla wrote:
>> On 10/06/2019 15:12, Pierre-Louis Bossart wrote:
>>>>>> +
>>>>>> +    if (dev_addr == SDW_BROADCAST_DEV_NUM) {
>>>>>> +        ctrl->fifo_status = 0;
>>>>>> +        ret = wait_for_completion_timeout(&ctrl->sp_cmd_comp,
>>>>>> +                          msecs_to_jiffies(TIMEOUT_MS));
>>>>> This is odd. The SoundWire spec does not handle writes to a single
>>>>> device or broadcast writes differently. I don't see a clear reason
>>>>> why you would only timeout for a broadcast write.
>>>> There is danger of blocking here without timeout.
>>> Right, and it's fine to add a timeout. The question is why add a
>>> timeout *only* for a broadcast operation? It should be added for
>>> every transaction IMO, unless you have a reason not to do so.
>> I did try this before, the issue is when we read/write registers from
>> interrupt handler, these can be deadlocked as we will be interrupt
>> handler waiting for another completion interrupt, which will never
>> happen unless we return from the first interrupt.
> I don't quite get the issue. With the Intel hardware we only deal with
> Master registers (some of which mirror the bus state) in the handler and
> will only modify Slave registers in the thread. All changes to Slave
> registers will be subject to a timeout as well as a check for no
> response or NAK. Not sure what is specific about your solution that
> requires a different handling of commands depending on which device
> number is used. It could very well be that you've uncovered a flaw in
> the bus design but I still don't see how it would be Qualcomm-specific?

Sorry It took bit more time for digging up the issue which I faced
previously to answer this query. This is now fixed and v2 patchset has
same handling for all the slave registers read/writes with no special


 \ /
  Last update: 2019-06-15 15:25    [W:0.072 / U:0.656 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site