From: Matthias Kaehlcke <mka@chromium.org>
To: Brian Norris <briannorris@chromium.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>,
Mark Brown <broonie@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] regulator: core: Sleep (not delay) in set_voltage()
Date: Mon, 18 Apr 2022 15:50:29 -0700 [thread overview]
Message-ID: <Yl3rNeaYTz0CPjmL@google.com> (raw)
In-Reply-To: <20220418141158.1.If0fc61a894f537b052ca41572aff098cf8e7e673@changeid>
On Mon, Apr 18, 2022 at 02:12:39PM -0700, Brian Norris wrote:
> These delays can be relatively large (e.g., hundreds of microseconds on
> RK3399 Gru systems). Per Documentation/timers/timers-howto.rst, that
> should usually use a sleeping delay. Let's use fsleep() to handle both
> large and small delays appropriately. This avoids burning a bunch of CPU
> time and hurting scheduling latencies when hitting regulators a lot
> (e.g., during cpufreq).
>
> The sleep vs. delay issue choice has been made differently over time --
> early versions of RK3399 Gru PWM-regulator support used usleep_range()
> in pwm-regulator.c. More of this got moved into the regulator core,
> in commits like:
>
> 73e705bf81ce regulator: core: Add set_voltage_time op
>
> At the same time, the sleep turned into a delay.
>
> It's OK to sleep here, as we aren't in an atomic contexts. (All our
> callers grab various mutexes already.)
>
> Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
prev parent reply other threads:[~2022-04-18 22:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-18 21:12 [PATCH 1/2] regulator: core: Sleep (not delay) in set_voltage() Brian Norris
2022-04-18 21:12 ` [PATCH 2/2] regulator: core: Replace _regulator_enable_delay() with fsleep() Brian Norris
2022-04-18 22:53 ` Matthias Kaehlcke
2022-04-20 16:28 ` Mark Brown
2022-04-20 18:24 ` Brian Norris
2022-04-20 21:11 ` Mark Brown
2022-04-18 22:50 ` Matthias Kaehlcke [this message]
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