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| author | Thierry Reding <thierry.reding@gmail.com> | 2019-10-21 12:41:40 +0200 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2019-10-21 16:48:52 +0200 |
| commit | 40a6b9a00930fd6b59aa2eb6135abc2efe5440c3 (patch) | |
| tree | baaaa4663cce1e5f33560d4d53e296f8e97dee95 | |
| parent | 54ecb8f7028c5eb3d740bb82b0f1d90f2df63c5c (diff) | |
| download | lwn-40a6b9a00930fd6b59aa2eb6135abc2efe5440c3.tar.gz lwn-40a6b9a00930fd6b59aa2eb6135abc2efe5440c3.zip | |
Revert "pwm: Let pwm_get_state() return the last implemented state"
It turns out that commit 01ccf903edd6 ("pwm: Let pwm_get_state() return
the last implemented state") causes backlight failures on a number of
boards. The reason is that some of the drivers do not write the full
state through to the hardware registers, which means that ->get_state()
subsequently does not return the correct state. Consumers which rely on
pwm_get_state() returning the current state will therefore get confused
and subsequently try to program a bad state.
Before this change can be made, existing drivers need to be more
carefully audited and fixed to behave as the framework expects. Until
then, keep the original behaviour of returning the software state that
was applied rather than reading the state back from hardware.
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Michal Vokáč <michal.vokac@ysoft.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
| -rw-r--r-- | drivers/pwm/core.c | 9 |
1 files changed, 1 insertions, 8 deletions
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index 6ad51aa60c03..f877e77d9184 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -472,14 +472,7 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state) if (err) return err; - /* - * .apply might have to round some values in *state, if possible - * read the actually implemented value back. - */ - if (chip->ops->get_state) - chip->ops->get_state(chip, pwm, &pwm->state); - else - pwm->state = *state; + pwm->state = *state; } else { /* * FIXME: restore the initial state in case of error. |