pwm: sifive: Call pwm_sifive_update_clock() while mutex is held

[ Upstream commit 45558b3abb87eeb2cedb8a59cb2699c120b5102a ]

As was documented in commit 0f02f491b786 ("pwm: sifive: Reduce time the
controller lock is held") a caller of pwm_sifive_update_clock() must
hold the mutex. So fix pwm_sifive_clock_notifier() to grab the lock.

While this necessity was only documented later, the race exists since
the driver was introduced.

Fixes: 9e37a53eb051 ("pwm: sifive: Add a driver for SiFive SoC PWM")
Reported-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Reviewed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Link: https://lore.kernel.org/r/20221018061656.1428111-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index 2d4fa5e..bb72393 100644 (file)
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -204,8 +204,11 @@ static int pwm_sifive_clock_notifier(struct notifier_block *nb,
        struct pwm_sifive_ddata *ddata =
                container_of(nb, struct pwm_sifive_ddata, notifier);
 
-       if (event == POST_RATE_CHANGE)
+       if (event == POST_RATE_CHANGE) {
+               mutex_lock(&ddata->lock);
                pwm_sifive_update_clock(ddata, ndata->new_rate);
+               mutex_unlock(&ddata->lock);
+       }
 
        return NOTIFY_OK;
 }