pwm: stm32: Enforce settings for PWM capture

The PWM capture assumes that the input selector is set to default
input and that the slave mode is disabled. Force reset state for
TISEL and SMCR registers to match this requirement.

Note that slave mode disabling is not a pre-requisite by itself
for capture mode, as hardware supports it for PWM capture.
However, the current implementation of the driver does not
allow slave mode for PWM capture. Setting slave mode for PWM
capture results in wrong capture values.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Acked-by: Lee Jones <lee@kernel.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
index a482f7e..62e397a 100644 (file)
--- a/drivers/pwm/pwm-stm32.c
+++ b/drivers/pwm/pwm-stm32.c
@@ -207,6 +207,10 @@ static int stm32_pwm_capture(struct pwm_chip *chip, struct pwm_device *pwm,
        regmap_write(priv->regmap, TIM_ARR, priv->max_arr);
        regmap_write(priv->regmap, TIM_PSC, psc);
 
+       /* Reset input selector to its default input and disable slave mode */
+       regmap_write(priv->regmap, TIM_TISEL, 0x0);
+       regmap_write(priv->regmap, TIM_SMCR, 0x0);
+
        /* Map TI1 or TI2 PWM input to IC1 & IC2 (or TI3/4 to IC3 & IC4) */
        regmap_update_bits(priv->regmap,
                           pwm->hwpwm < 2 ? TIM_CCMR1 : TIM_CCMR2,

diff --git a/include/linux/mfd/stm32-timers.h b/include/linux/mfd/stm32-timers.h
index 5f5c43f..1b94325 100644 (file)
--- a/include/linux/mfd/stm32-timers.h
+++ b/include/linux/mfd/stm32-timers.h
@@ -31,6 +31,7 @@
 #define TIM_BDTR       0x44    /* Break and Dead-Time Reg */
 #define TIM_DCR                0x48    /* DMA control register    */
 #define TIM_DMAR       0x4C    /* DMA register for transfer */
+#define TIM_TISEL      0x68    /* Input Selection         */
 
 #define TIM_CR1_CEN    BIT(0)  /* Counter Enable          */
 #define TIM_CR1_DIR    BIT(4)  /* Counter Direction       */