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From: Martin Blumenstingl <>
	Martin Blumenstingl <>,,,,
Subject: [PATCH v2 0/1] pwm: meson: fix scheduling while atomic issue
Date: Mon,  1 Apr 2019 19:57:47 +0200
Message-ID: <> (raw)

Back in January a "BUG: scheduling while atomic" error showed up during
boot on my Meson8b Odroid-C1 (which uses a PWM regulator as CPU supply).
The call trace comes down to:

Jerome has also seen the same problem but from pwm-leds (instead of a
pwm-regulator). He posted a patch which replaces the spinlock with a
mutex. That works. I believe we can optimize this by reducing the time
where the lock is held - that also allows to keep the spin-lock.

Analyzing this issue helped me understand the pwm-meson driver better.
My plan is to send some cleanups after this single fix is merged. The
goal of these cleanups is to re-use more of the goodies from the PWM
core in the pwm-meson driver as well as to address issues spotted by
Uwe Kleine-König (these issues violate the PWM API, but none of these
result in breakage of the boards/.dts that we currently have). These
follow-up patches can be found here: [1].

Dependencies: none

Target version: please queue this for -fixes so it makes it's way into
v5.1-rc (so we can get it backported from there, because this issue has
existed since the pwm-meson driver was introduced).

changes since v1 at [2]:
- added comment about usage of the spinlock as suggested by
  Uwe Kleine-König (thank you)
- collected Uwe Kleine-König's Reviewed-by


Martin Blumenstingl (1):
  pwm: meson: use the spin-lock only to protect register modifications

 drivers/pwm/pwm-meson.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)


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Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-01 17:57 Martin Blumenstingl [this message]
2019-04-01 17:57 ` [PATCH v2 1/1] pwm: meson: use the spin-lock only to protect register modifications Martin Blumenstingl
2019-04-03 11:21   ` Neil Armstrong
2019-05-09 14:52   ` Thierry Reding

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