[PATCH 06/14] ASoC: SOF: add a power status IPC
Mark Brown
broonie at kernel.org
Fri Mar 20 13:19:52 CET 2020
On Fri, Mar 20, 2020 at 12:52:03PM +0100, Guennadi Liakhovetski wrote:
> On Fri, Mar 13, 2020 at 02:39:56PM +0000, Mark Brown wrote:
> > On Thu, Mar 12, 2020 at 03:44:21PM +0100, Guennadi Liakhovetski wrote:
> > > #endif
> > > + atomic_set(&sdev->reset_count, 0);
> > > dev_set_drvdata(dev, sdev);
> > Do we really need to use atomics for this? They are hard to use
> > correctly.
> This variable is accessed from 2 contexts: it's incremented by the SOF
> driver, when the firmware has booted and it's read by the SOF
> VirtIO backend vhost-be.c when receiving a resume request from the guest.
> Timewise the variable will only be incremented during the DSP resume /
> power up, while the VirtIO back end is waiting for the resume to complete in
> pm_runtime_get_sync(). And only after that it reads the variable. But that
> can happen on different CPUs. Whereas I think that runtime PM will sync
> caches somewhere during the process, I think it is better to access the
> variable in an SMP-safe way, e.g. using atomic operations.
That doesn't address my concern - to repeat, my concern is that atomics
are hard to use correctly. Is there no other concurrency primitive (for
example this sounds like a completion) which can be used?
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