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: __mutex_lock clk_prepare_lock clk_core_get_rate meson_pwm_apply .. dev_pm_opp_set_rate ..
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 [0] http://lists.infradead.org/pipermail/linux-amlogic/2019-January/009690.html [1] https://github.com/xdarklight/linux/commits/meson-pwm-for-5.2-v1 [2] https://patchwork.kernel.org/cover/10867757/ 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(-) -- 2.21.0