Re: [PATCH v3] regmap: add iopoll-like atomic polling macro

[Sameer Pujar]

On 1/9/2020 11:30 AM, Dmitry Osipenko wrote:
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>
> 09.01.2020 08:09, Sameer Pujar ÐÐÑÐÑ:
> > This patch adds a macro 'regmap_read_poll_timeout_atomic' that works
> > similar to 'readx_poll_timeout_atomic' defined in linux/iopoll.h; This
> > is atomic version of already available 'regmap_read_poll_timeout' macro.
> >
> > It should be noted that above atomic macro cannot be used by all regmaps.
> > If the regmap is set up for atomic use (flat or no cache and MMIO) then
> > only it can use.
> >
> > Signed-off-by: Sameer Pujar <spujar@xxxxxxxxxx>
> > ---
> Could you please explain what is the targeted use-case here?

I was trying to use regmap_read_poll_timeout() to poll for status change 
of a register. This resulted in "BUG: scheduling while atomic". The 
callback function, in which I was trying to use the macro, runs in 
atomic context. Hence new atomic macro is added. I was checking ALSA 
playback/capture and trigger() callback had to monitor some register status.

In general, the new macro can be used in atomic callbacks where regmap 
interface is used and polling is required.