pwm: meson: Read the full hardware state in meson_pwm_get_state()

Update the meson_pwm_get_state() implementation to take care of all
information in the registers instead of only reading the "enabled"
state.

The PWM output is only enabled if two conditions are met:
1. the per-channel clock is enabled
2. the PWM output is enabled

Calculate the PWM period and duty cycle using the reverse formula which
we already have in meson_pwm_calc() and update struct pwm_state with the
results.

As result of this /sys/kernel/debug/pwm now shows the PWM state set by
the bootloader (or firmware) after booting Linux.
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-meson.c

@@ -287,19 +287,65 @@ static int meson_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	return 0;
 }
 
+static unsigned int meson_pwm_cnt_to_ns(struct pwm_chip *chip,
+					struct pwm_device *pwm, u32 cnt)
+{
+	struct meson_pwm *meson = to_meson_pwm(chip);
+	struct meson_pwm_channel *channel;
+	unsigned long fin_freq;
+	u32 fin_ns;
+
+	/* to_meson_pwm() can only be used after .get_state() is called */
+	channel = &meson->channels[pwm->hwpwm];
+
+	fin_freq = clk_get_rate(channel->clk);
+	if (fin_freq == 0)
+		return 0;
+
+	fin_ns = div_u64(NSEC_PER_SEC, fin_freq);
+
+	return cnt * fin_ns * (channel->pre_div + 1);
+}
+
 static void meson_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 				struct pwm_state *state)
 {
 	struct meson_pwm *meson = to_meson_pwm(chip);
-	u32 value, mask;
+	struct meson_pwm_channel_data *channel_data;
+	struct meson_pwm_channel *channel;
+	u32 value, tmp;
 
 	if (!state)
 		return;
 
-	mask = meson_pwm_per_channel_data[pwm->hwpwm].pwm_en_mask;
+	channel = &meson->channels[pwm->hwpwm];
+	channel_data = &meson_pwm_per_channel_data[pwm->hwpwm];
 
 	value = readl(meson->base + REG_MISC_AB);
-	state->enabled = (value & mask) != 0;
+
+	tmp = channel_data->pwm_en_mask | channel_data->clk_en_mask;
+	state->enabled = (value & tmp) == tmp;
+
+	tmp = value >> channel_data->clk_div_shift;
+	channel->pre_div = FIELD_GET(MISC_CLK_DIV_MASK, tmp);
+
+	value = readl(meson->base + channel_data->reg_offset);
+
+	channel->lo = FIELD_GET(PWM_LOW_MASK, value);
+	channel->hi = FIELD_GET(PWM_HIGH_MASK, value);
+
+	if (channel->lo == 0) {
+		state->period = meson_pwm_cnt_to_ns(chip, pwm, channel->hi);
+		state->duty_cycle = state->period;
+	} else if (channel->lo >= channel->hi) {
+		state->period = meson_pwm_cnt_to_ns(chip, pwm,
+						    channel->lo + channel->hi);
+		state->duty_cycle = meson_pwm_cnt_to_ns(chip, pwm,
+							channel->hi);
+	} else {
+		state->period = 0;
+		state->duty_cycle = 0;
+	}
 }
 
 static const struct pwm_ops meson_pwm_ops = {