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

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Message-ID: <b9f5459f-007e-3139-a3cf-c7dfd3fc335a@nvidia.com>
Date:   Thu, 9 Jan 2020 12:54:31 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <broonie@...nel.org>
CC:     <jonathanh@...dia.com>, <linux-kernel@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v3] regmap: add iopoll-like atomic polling macro

On 1/9/2020 11:30 AM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 09.01.2020 08:09, Sameer Pujar пишет:
>> 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@...dia.com>
>> ---
> 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.