Re: [PATCH 2/4] pwm: rockchip: Allow polarity invert on rk3288

Thierry

On Tue, Aug 19, 2014 at 12:18 AM, Thierry Reding
[off-list ref] wrote:

On Mon, Aug 18, 2014 at 10:09:07AM -0700, Doug Anderson wrote:
[...]

quoted

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
 #define PWM_LP_DISABLE               (0 << 8)

@@ -32,6 +34,7 @@ struct rockchip_pwm_chip {
      struct pwm_chip chip;
      struct clk *clk;
      const struct rockchip_pwm_data *data;
+     enum pwm_polarity polarity;

Why do you need this field? struct pwm_device already has a copy of it.

OK, good point.

quoted

@@ -74,10 +78,14 @@ static void rockchip_pwm_set_enable_v2(struct pwm_chip *chip, bool enable)
 {
      struct rockchip_pwm_chip *pc = to_rockchip_pwm_chip(chip);
      u32 enable_conf = PWM_OUTPUT_LEFT | PWM_LP_DISABLE | PWM_ENABLE |
-                       PWM_CONTINUOUS | PWM_DUTY_POSITIVE |
-                       PWM_INACTIVE_NEGATIVE;
+                       PWM_CONTINUOUS;
      u32 val;

+     if (pc->polarity == PWM_POLARITY_INVERSED)
+             enable_conf |= PWM_DUTY_NEGATIVE | PWM_INACTIVE_POSITIVE;
+     else
+             enable_conf |= PWM_DUTY_POSITIVE | PWM_INACTIVE_NEGATIVE;

I have a feeling you're going to answer the above question with: "Because
it's needed here". If so, my reply would be: "Then this function should
take a struct pwm_device instead of struct pwm_chip."

OK.  I've chosen to have it take a pwm_device AND a pwm_chip.  It is a
little redundant because a pwm_device has a pointer to its pwm_chip,
but it follows the lead of all of the callbacks in "struct pwm_ops".
If you'd like me to spin it to take only a pwm_device I'm happy to.

quoted

@@ -173,6 +195,7 @@ static const struct rockchip_pwm_data pwm_data_v2 = {
              .ctrl = 0x0c,
      },
      .prescaler = 1,
+     .has_invert = 1,

Since has_invert is a boolean, the proper value here would be "true".

Done.

quoted

@@ -228,6 +252,10 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
      pc->data = id->data;
      pc->chip.dev = &pdev->dev;
      pc->chip.ops = &rockchip_pwm_ops;
+     if (pc->data->has_invert) {
+             pc->chip.of_xlate = of_pwm_xlate_with_flags;
+             pc->chip.of_pwm_n_cells = 3;
+     }
      pc->chip.base = -1;
      pc->chip.npwm = 1;

I suggest to rewrite the above as follows for readability:

        pc->data = id->data;
        pc->chip.dev = &pdev->dev;
        pc->chip.ops = &rockchip_pwm_ops;
        pc->chip.base = -1;
        pc->chip.npwm = 1;

Done.

+       if (pc->data->has_invert) {
+               pc->chip.of_xlate = of_pwm_xlate_with_flags;
+               pc->chip.of_pwm_n_cells = 3;
+       }

Thierry