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author | Hans de Goede <hdegoede@redhat.com> | 2020-09-03 13:23:26 +0200 |
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committer | Hans de Goede <hdegoede@redhat.com> | 2020-09-06 15:38:00 +0200 |
commit | d6d54bacb1dd02a31ed9d8e3db028639da292615 (patch) | |
tree | 5df2513453779547c2c137cbef1b4aa28a47025e /drivers/pwm/pwm-lpss.c | |
parent | pwm: lpss: Add pwm_lpss_prepare_enable() helper (diff) | |
download | linux-d6d54bacb1dd02a31ed9d8e3db028639da292615.tar.xz linux-d6d54bacb1dd02a31ed9d8e3db028639da292615.zip |
pwm: lpss: Make pwm_lpss_apply() not rely on existing hardware state
Before this commit pwm_lpss_apply() was assuming 2 pre-conditions
were met by the existing hardware state:
1. That the base-unit and on-time-div read back from the
control register are those actually in use, so that it
can skip setting the update bit if the read-back value
matches the desired values.
2. That the controller is enabled when the cached
pwm_state.enabled says that the controller is enabled.
As the long history of fixes for subtle (often suspend/resume)
lpss-pwm issues shows, these assumptions are not necessary
always true.
1. Specifically is not true on some (*) Cherry Trail devices
with a nasty GFX0._PS3 method which: a. saves the ctrl reg value.
b. sets the base-unit to 0 and writes the update bit to apply/commit
c. restores the original ctrl value without setting the update bit,
so that the 0 base-unit value is still in use.
2. Assumption 2. currently is true, but only because of the code which
saves/restores the state on suspend/resume. By convention restoring the
PWM state should be done by the PWM consumer and the presence of this
code in the pmw-lpss driver is a bug. Therefor the save/restore code will
be dropped in the next patch in this series, after which this assumption
also is no longer true.
This commit changes the pwm_lpss_apply() to not make any assumptions about
the state the hardware is in. Instead it makes pwm_lpss_apply() always
fully program the PWM controller, making it much less fragile.
*) Seen on the Acer One 10 S1003, Lenovo Ideapad Miix 310 and 320 models
and various Medion models.
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200903112337.4113-7-hdegoede@redhat.com
Diffstat (limited to 'drivers/pwm/pwm-lpss.c')
-rw-r--r-- | drivers/pwm/pwm-lpss.c | 21 |
1 files changed, 9 insertions, 12 deletions
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 8a136ba2a583..9c5c7217c9b6 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -85,7 +85,7 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, unsigned long long on_time_div; unsigned long c = lpwm->info->clk_rate, base_unit_range; unsigned long long base_unit, freq = NSEC_PER_SEC; - u32 orig_ctrl, ctrl; + u32 ctrl; do_div(freq, period_ns); @@ -104,16 +104,14 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, do_div(on_time_div, period_ns); on_time_div = 255ULL - on_time_div; - orig_ctrl = ctrl = pwm_lpss_read(pwm); + ctrl = pwm_lpss_read(pwm); ctrl &= ~PWM_ON_TIME_DIV_MASK; ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT); ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT; ctrl |= on_time_div; - if (orig_ctrl != ctrl) { - pwm_lpss_write(pwm, ctrl); - pwm_lpss_write(pwm, ctrl | PWM_SW_UPDATE); - } + pwm_lpss_write(pwm, ctrl); + pwm_lpss_write(pwm, ctrl | PWM_SW_UPDATE); } static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond) @@ -124,8 +122,7 @@ static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond) static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, - const struct pwm_state *state, - bool enable) + const struct pwm_state *state) { int ret; @@ -134,12 +131,12 @@ static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm, return ret; pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period); - pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == false); + pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false); ret = pwm_lpss_wait_for_update(pwm); if (ret) return ret; - pwm_lpss_cond_enable(pwm, enable && lpwm->info->bypass == true); + pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true); return 0; } @@ -152,11 +149,11 @@ static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm, if (state->enabled) { if (!pwm_is_enabled(pwm)) { pm_runtime_get_sync(chip->dev); - ret = pwm_lpss_prepare_enable(lpwm, pwm, state, true); + ret = pwm_lpss_prepare_enable(lpwm, pwm, state); if (ret) pm_runtime_put(chip->dev); } else { - ret = pwm_lpss_prepare_enable(lpwm, pwm, state, false); + ret = pwm_lpss_prepare_enable(lpwm, pwm, state); } } else if (pwm_is_enabled(pwm)) { pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE); |