pwm: sti: Fix PWM prescaler handling

This patch fixes the pwm driver to write the complete 8 bits of
the prescaler value to the PWM Control register.

Signed-off-by: Ajit Pal Singh <ajitpal.singh@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

1 files changed, 27 insertions, 11 deletions

diff --git a/drivers/pwm/pwm-sti.c b/drivers/pwm/pwm-sti.c
index 0b714e45e5c0..76346e32f403 100644
--- a/drivers/pwm/pwm-sti.c
+++ b/drivers/pwm/pwm-sti.c
@@ -25,10 +25,13 @@
 #define STI_DS_REG(ch)  (4 * (ch))      /* Channel's Duty Cycle register */
 #define STI_PWMCR       0x50            /* Control/Config register */
 #define STI_INTEN       0x54            /* Interrupt Enable/Disable register */
+#define PWM_PRESCALE_LOW_MASK           0x0f
+#define PWM_PRESCALE_HIGH_MASK          0xf0
 
 /* Regfield IDs */
 enum {
-        PWMCLK_PRESCALE,
+        PWMCLK_PRESCALE_LOW,
+        PWMCLK_PRESCALE_HIGH,
         PWM_EN,
         PWM_INT_EN,
 
@@ -49,7 +52,8 @@ struct sti_pwm_chip {
         unsigned long clk_rate;
         struct regmap *regmap;
         struct sti_pwm_compat_data *cdata;
-        struct regmap_field *prescale;
+        struct regmap_field *prescale_low;
+        struct regmap_field *prescale_high;
         struct regmap_field *pwm_en;
         struct regmap_field *pwm_int_en;
         unsigned long *pwm_periods;
@@ -58,7 +62,8 @@ struct sti_pwm_chip {
 };
 
 static const struct reg_field sti_pwm_regfields[MAX_REGFIELDS] = {
-        [PWMCLK_PRESCALE]       = REG_FIELD(STI_PWMCR, 0, 3),
+        [PWMCLK_PRESCALE_LOW]   = REG_FIELD(STI_PWMCR, 0, 3),
+        [PWMCLK_PRESCALE_HIGH]  = REG_FIELD(STI_PWMCR, 11, 14),
         [PWM_EN]                = REG_FIELD(STI_PWMCR, 9, 9),
         [PWM_INT_EN]            = REG_FIELD(STI_INTEN, 0, 0),
 };
@@ -109,10 +114,10 @@ static int sti_pwm_cmp_periods(const void *key, const void *elt)
  * For STiH4xx PWM IP, the PWM period is fixed to 256 local clock cycles.
  * The only way to change the period (apart from changing the PWM input clock)
  * is to change the PWM clock prescaler.
- * The prescaler is of 4 bits, so only 16 prescaler values and hence only
- * 16 possible period values are supported (for a particular clock rate).
+ * The prescaler is of 8 bits, so 256 prescaler values and hence
+ * 256 possible period values are supported (for a particular clock rate).
  * The requested period will be applied only if it matches one of these
- * 16 values.
+ * 256 values.
  */
 static int sti_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
                          int duty_ns, int period_ns)
@@ -154,7 +159,13 @@ static int sti_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
         if (ret)
                 return ret;
 
-        ret = regmap_field_write(pc->prescale, prescale);
+        ret = regmap_field_write(pc->prescale_low,
+                                 prescale & PWM_PRESCALE_LOW_MASK);
+        if (ret)
+                goto clk_dis;
+
+        ret = regmap_field_write(pc->prescale_high,
+                                 (prescale & PWM_PRESCALE_HIGH_MASK) >> 4);
         if (ret)
                 goto clk_dis;
 
@@ -222,10 +233,15 @@ static int sti_pwm_probe_dt(struct sti_pwm_chip *pc)
 
         reg_fields = cdata->reg_fields;
 
-        pc->prescale = devm_regmap_field_alloc(dev, pc->regmap,
-                                               reg_fields[PWMCLK_PRESCALE]);
-        if (IS_ERR(pc->prescale))
-                return PTR_ERR(pc->prescale);
+        pc->prescale_low = devm_regmap_field_alloc(dev, pc->regmap,
+                                        reg_fields[PWMCLK_PRESCALE_LOW]);
+        if (IS_ERR(pc->prescale_low))
+                return PTR_ERR(pc->prescale_low);
+
+        pc->prescale_high = devm_regmap_field_alloc(dev, pc->regmap,
+                                        reg_fields[PWMCLK_PRESCALE_HIGH]);
+        if (IS_ERR(pc->prescale_high))
+                return PTR_ERR(pc->prescale_high);
 
         pc->pwm_en = devm_regmap_field_alloc(dev, pc->regmap,
                                              reg_fields[PWM_EN]);