linux-kernel - Re: [PATCH 4/4] soundwire: stream: Move remaining register accesses over to no

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Date:   Tue, 15 Nov 2022 11:05:20 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
CC:     <vkoul@...nel.org>, <alsa-devel@...a-project.org>,
        <patches@...nsource.cirrus.com>, <linux-kernel@...r.kernel.org>,
        <sanyog.r.kale@...el.com>, <yung-chuan.liao@...ux.intel.com>
Subject: Re: [PATCH 4/4] soundwire: stream: Move remaining register accesses
 over to no_pm

On Mon, Nov 14, 2022 at 10:04:55AM -0600, Pierre-Louis Bossart wrote:
> 
> 
> On 11/14/22 04:29, Charles Keepax wrote:
> > There is no need to play with the runtime reference everytime a register
> > is accessed. All the remaining "pm" style register accesses trace back
> > to 4 functions:
> > 
> > sdw_prepare_stream
> > sdw_deprepare_stream
> > sdw_enable_stream
> > sdw_disable_stream
> > 
> > Any sensible implementation will need to hold a runtime reference
> > across all those functions, it makes no sense to be allowing the
> > device/bus to suspend whilst streams are being prepared/enabled. And
> > certainly in the case of the all existing users, they all call these
> > functions from hw_params/prepare/trigger/hw_free callbacks in ALSA,
> > which will have already runtime resumed all the audio devices
> > associated during the open callback.
> > 
> > Signed-off-by: Charles Keepax <ckeepax@...nsource.cirrus.com>
> 
> I tend to agree with this one, and if this ever fails that would point
> to a miss at a higher-level we'd need to address.

Exactly my concern here is the core is trying to be helpful, but
really it is just going to be hiding bugs in the callers.

Thanks,
Charles