diff options
Diffstat (limited to '0001-pwm-lpss-Fix-get_state-runtime-pm-reference-handling.patch')
| -rw-r--r-- | 0001-pwm-lpss-Fix-get_state-runtime-pm-reference-handling.patch | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/0001-pwm-lpss-Fix-get_state-runtime-pm-reference-handling.patch b/0001-pwm-lpss-Fix-get_state-runtime-pm-reference-handling.patch new file mode 100644 index 000000000..1e07d8e45 --- /dev/null +++ b/0001-pwm-lpss-Fix-get_state-runtime-pm-reference-handling.patch @@ -0,0 +1,100 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Hans de Goede <hdegoede@redhat.com> +Date: Tue, 12 May 2020 00:39:24 +0200 +Subject: [PATCH] pwm: lpss: Fix get_state runtime-pm reference handling + +Before commit cfc4c189bc70 ("pwm: Read initial hardware state at request +time"), a driver's get_state callback would get called once per PWM from +pwmchip_add(). + +pwm-lpss' runtime-pm code was relying on this, getting a runtime-pm ref for +PWMs which are enabled at probe time from within its get_state callback, +before enabling runtime-pm. + +The change to calling get_state at request time causes a number of +problems: + +1. PWMs enabled at probe time may get runtime suspended before they are +requested, causing e.g. a LCD backlight controlled by the PWM to turn off. + +2. When the request happens when the PWM has been runtime suspended, the +ctrl register will read all 1 / 0xffffffff, causing get_state to store +bogus values in the pwm_state. + +3. get_state was using an async pm_runtime_get() call, because it assumed +that runtime-pm has not been enabled yet. If shortly after the request an +apply call is made, then the pwm_lpss_is_updating() check may trigger +because the resume triggered by the pm_runtime_get() call is not complete +yet, so the ctrl register still reads all 1 / 0xffffffff. + +This commit fixes these issues by moving the initial pm_runtime_get() call +for PWMs which are enabled at probe time to the pwm_lpss_probe() function; +and by making get_state take a runtime-pm ref before reading the ctrl reg. + +BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1828927 +Fixes: cfc4c189bc70 ("pwm: Read initial hardware state at request time") +Cc: stable@vger.kernel.org +Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> +Signed-off-by: Hans de Goede <hdegoede@redhat.com> +Upstream Status: https://lore.kernel.org/linux-acpi/5f15f6bc-8650-d86e-893f-0d41557c57c7@redhat.com/ +--- + drivers/pwm/pwm-lpss.c | 15 +++++++++++---- + 1 file changed, 11 insertions(+), 4 deletions(-) + +diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c +index 75bbfe5f3bc2..9d965ffe66d1 100644 +--- a/drivers/pwm/pwm-lpss.c ++++ b/drivers/pwm/pwm-lpss.c +@@ -158,7 +158,6 @@ static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm, + return 0; + } + +-/* This function gets called once from pwmchip_add to get the initial state */ + static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_state *state) + { +@@ -167,6 +166,8 @@ static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + unsigned long long base_unit, freq, on_time_div; + u32 ctrl; + ++ pm_runtime_get_sync(chip->dev); ++ + base_unit_range = BIT(lpwm->info->base_unit_bits); + + ctrl = pwm_lpss_read(pwm); +@@ -187,8 +188,7 @@ static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + state->polarity = PWM_POLARITY_NORMAL; + state->enabled = !!(ctrl & PWM_ENABLE); + +- if (state->enabled) +- pm_runtime_get(chip->dev); ++ pm_runtime_put(chip->dev); + } + + static const struct pwm_ops pwm_lpss_ops = { +@@ -202,7 +202,8 @@ struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r, + { + struct pwm_lpss_chip *lpwm; + unsigned long c; +- int ret; ++ int i, ret; ++ u32 ctrl; + + if (WARN_ON(info->npwm > MAX_PWMS)) + return ERR_PTR(-ENODEV); +@@ -232,6 +233,12 @@ struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r, + return ERR_PTR(ret); + } + ++ for (i = 0; i < lpwm->info->npwm; i++) { ++ ctrl = pwm_lpss_read(&lpwm->chip.pwms[i]); ++ if (ctrl & PWM_ENABLE) ++ pm_runtime_get(dev); ++ } ++ + return lpwm; + } + EXPORT_SYMBOL_GPL(pwm_lpss_probe); +-- +2.26.2 + |