Hello, On Sun, Mar 24, 2019 at 11:02:17PM +0100, Martin Blumenstingl wrote: > Holding the spin-lock for all of the code in meson_pwm_apply() can > result in a "BUG: scheduling while atomic". This can happen because > clk_get_rate() (which is called from meson_pwm_calc()) may sleep. > Only hold the spin-lock when modifying registers to solve this. > > The reason why we need a spin-lock in the driver is because the > REG_MISC_AB register is shared between the two channels provided by one > PWM controller. The only functions where REG_MISC_AB is modified are > meson_pwm_enable() and meson_pwm_disable() so the register reads/writes > in there need to be protected by the spin-lock. > > The original code also used the spin-lock to protect the values in > struct meson_pwm_channel. This could be necessary if two consumers can > use the same PWM channel. However, PWM core doesn't allow this so we > don't need to protect the values in struct meson_pwm_channel with a > lock. > > Fixes: 211ed630753d2f ("pwm: Add support for Meson PWM Controller") > Signed-off-by: Martin Blumenstingl <martin.blumensti...@googlemail.com>
Looks right. Reviewed-by: Uwe Kleine-König <u.kleine-koe...@pengutronix.de> Bonus points for adding a comment to struct meson_pwm::lock. Something like: /* * Protects register access to the MISC_AB register that is * shared between the two PWMs. */ Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |