pwm: fsl-ftm: Use write protection for prescaler & polarity

Modifying the prescaler or polarity value must be done with the
write protection disabled. Currently this is working by chance as
the write protection is in a disabled state by default.
This patch makes sure that we enable/disable the write protection
when needed.

Signed-off-by: Patrick Havelange <patrick.havelange@essensium.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/drivers/pwm/pwm-fsl-ftm.c b/drivers/pwm/pwm-fsl-ftm.c
index e14b8e191cd419c6f4cd74b5c9ef1fe2b75bf305..6a4106c65cb4b42964a33c213bc351e628872249 100644 (file)
--- a/drivers/pwm/pwm-fsl-ftm.c
+++ b/drivers/pwm/pwm-fsl-ftm.c
@@ -63,6 +63,21 @@ static inline struct fsl_pwm_chip *to_fsl_chip(struct pwm_chip *chip)
        return container_of(chip, struct fsl_pwm_chip, chip);
 }
 
+static void ftm_clear_write_protection(struct fsl_pwm_chip *fpc)
+{
+       u32 val;
+
+       regmap_read(fpc->regmap, FTM_FMS, &val);
+       if (val & FTM_FMS_WPEN)
+               regmap_update_bits(fpc->regmap, FTM_MODE, FTM_MODE_WPDIS,
+                                  FTM_MODE_WPDIS);
+}
+
+static void ftm_set_write_protection(struct fsl_pwm_chip *fpc)
+{
+       regmap_update_bits(fpc->regmap, FTM_FMS, FTM_FMS_WPEN, FTM_FMS_WPEN);
+}
+
 static bool fsl_pwm_periodcfg_are_equal(const struct fsl_pwm_periodcfg *a,
                                        const struct fsl_pwm_periodcfg *b)
 {
@@ -257,6 +272,8 @@ static int fsl_pwm_apply_config(struct fsl_pwm_chip *fpc,
                do_write_period = true;
        }
 
+       ftm_clear_write_protection(fpc);
+
        if (do_write_period) {
                regmap_update_bits(fpc->regmap, FTM_SC, FTM_SC_CLK_MASK,
                                   FTM_SC_CLK(periodcfg.clk_select));
@@ -283,6 +300,8 @@ static int fsl_pwm_apply_config(struct fsl_pwm_chip *fpc,
                                               fpc->period.mod_period + 1);
        newstate->duty_cycle = fsl_pwm_ticks_to_ns(fpc, duty);
 
+       ftm_set_write_protection(fpc);
+
        return 0;
 }
 
@@ -367,6 +386,8 @@ static int fsl_pwm_init(struct fsl_pwm_chip *fpc)
 static bool fsl_pwm_volatile_reg(struct device *dev, unsigned int reg)
 {
        switch (reg) {
+       case FTM_FMS:
+       case FTM_MODE:
        case FTM_CNT:
                return true;
        }