linux-kernel - Re: [PATCH 5/7] soundwire: intel: Don't disable interrupt until children are removed

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Date:   Mon, 12 Sep 2022 19:12:01 +0200
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>, vkoul@...nel.org,
        yung-chuan.liao@...ux.intel.com, lgirdwood@...il.com,
        peter.ujfalusi@...ux.intel.com, ranjani.sridharan@...ux.intel.com,
        kai.vehmanen@...ux.intel.com, daniel.baluta@....com,
        sanyog.r.kale@...el.com, broonie@...nel.org
Cc:     patches@...nsource.cirrus.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, sound-open-firmware@...a-project.org
Subject: Re: [PATCH 5/7] soundwire: intel: Don't disable interrupt until
 children are removed



On 9/12/22 17:36, Richard Fitzgerald wrote:
> On 12/09/2022 11:53, Pierre-Louis Bossart wrote:
>>
>>
>> On 9/7/22 12:14, Richard Fitzgerald wrote:
>>> The cadence_master code needs the interrupt to complete message
>>> transfers.
>>> When the bus driver is being removed child drivers are removed, and
>>> their
>>> remove actions might need bus transactions.
>>>
>>> Use the sdw_master_ops.remove callback to disable the interrupt handling
>>> only after the child drivers have been removed.
>>>
>>> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
>>> ---
>>>   drivers/soundwire/intel.c | 9 ++++++++-
>>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
>>> index 01be62fa6c83..d5e723a9c80b 100644
>>> --- a/drivers/soundwire/intel.c
>>> +++ b/drivers/soundwire/intel.c
>>> @@ -1255,6 +1255,13 @@ static int intel_prop_read(struct sdw_bus *bus)
>>>       return 0;
>>>   }
>>>   +static void intel_bus_remove(struct sdw_bus *bus)
>>> +{
>>> +    struct sdw_cdns *cdns = bus_to_cdns(bus);
>>> +
>>> +    sdw_cdns_enable_interrupt(cdns, false);
>>
>> don't you need to check for any on-going transactions on the bus?
>>
> 
> As all the child drivers have removed, I think the only other place that
> can generate bus transactions is the PING handler but
> sdw_cdns_enable_interrupt(false) calls cancel_work_sync() to
> cancel the cdns->work and it sets a flag so that it will not be
> re-queued.
> 
>> I wonder if there could be a corner case where there are no child
>> devices but still a device physically attached to the bus. I am not sure
>> if the 'no devices left' is a good-enough indication of no activity on
>> the bus.
>>
> 
> As above - yes there could, but sdw_cdns_enable_interrupt(false) will
> cancel the work and stop it being re-queued.

Ah yes, I forgot that part, thanks!

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>