[PATCH] pwm: meson: add support for S4 chip family

[Heiner Kallweit <hkallweit1@gmail.com>]

This adds pwm support for (at least) the s4 chip family. The extension
is based on the vendor driver that can be found at [0]. There the
version with the new clock handling is called meson-v2-pwm.
Central change is that the clock is now fully provided by the SoC clock
core. The multiplexer isn't any longer part of the pwm block.

This was tested on a sc2-based system that uses the same pwm block.

[0] https://github.com/khadas/linux/blob/khadas-vims-5.4.y/drivers/pwm/pwm-meson.c

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
Adding the amlogic,meson-s4-pwm compatible to the documentation was part
of the yaml conversion already.
---
 drivers/pwm/pwm-meson.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
index 16d79ca5d..7a93fdada 100644
--- a/drivers/pwm/pwm-meson.c
+++ b/drivers/pwm/pwm-meson.c
@@ -98,6 +98,7 @@ struct meson_pwm_channel {
 struct meson_pwm_data {
 	const char * const *parent_names;
 	unsigned int num_parents;
+	unsigned int ext_clk:1;
 };
 
 struct meson_pwm {
@@ -158,6 +159,7 @@ static int meson_pwm_calc(struct meson_pwm *meson, struct pwm_device *pwm,
 	struct meson_pwm_channel *channel = &meson->channels[pwm->hwpwm];
 	unsigned int duty, period, pre_div, cnt, duty_cnt;
 	unsigned long fin_freq;
+	int err;
 
 	duty = state->duty_cycle;
 	period = state->period;
@@ -165,6 +167,14 @@ static int meson_pwm_calc(struct meson_pwm *meson, struct pwm_device *pwm,
 	if (state->polarity == PWM_POLARITY_INVERSED)
 		duty = period - duty;
 
+	if (meson->data->ext_clk) {
+		err = clk_set_rate(channel->clk, 0xffffUL * NSEC_PER_SEC / period);
+		if (err) {
+			dev_err(meson->chip.dev, "failed to set pwm clock rate\n");
+			return err;
+		}
+	}
+
 	fin_freq = clk_get_rate(channel->clk);
 	if (fin_freq == 0) {
 		dev_err(meson->chip.dev, "invalid source clock frequency\n");
@@ -173,10 +183,14 @@ static int meson_pwm_calc(struct meson_pwm *meson, struct pwm_device *pwm,
 
 	dev_dbg(meson->chip.dev, "fin_freq: %lu Hz\n", fin_freq);
 
-	pre_div = div64_u64(fin_freq * (u64)period, NSEC_PER_SEC * 0xffffLL);
-	if (pre_div > MISC_CLK_DIV_MASK) {
-		dev_err(meson->chip.dev, "unable to get period pre_div\n");
-		return -EINVAL;
+	if (meson->data->ext_clk) {
+		pre_div = 0;
+	} else {
+		pre_div = div64_u64(fin_freq * (u64)period, NSEC_PER_SEC * 0xffffLL);
+		if (pre_div > MISC_CLK_DIV_MASK) {
+			dev_err(meson->chip.dev, "unable to get period pre_div\n");
+			return -EINVAL;
+		}
 	}
 
 	cnt = div64_u64(fin_freq * (u64)period, NSEC_PER_SEC * (pre_div + 1));
@@ -445,6 +459,10 @@ static const struct meson_pwm_data pwm_g12a_ee_data = {
 	.num_parents = ARRAY_SIZE(pwm_g12a_ee_parent_names),
 };
 
+static const struct meson_pwm_data pwm_s4_data = {
+	.ext_clk = 1,
+};
+
 static const struct of_device_id meson_pwm_matches[] = {
 	{
 		.compatible = "amlogic,meson8b-pwm",
@@ -478,6 +496,10 @@ static const struct of_device_id meson_pwm_matches[] = {
 		.compatible = "amlogic,meson-g12a-ao-pwm-cd",
 		.data = &pwm_g12a_ao_cd_data
 	},
+	{
+		.compatible = "amlogic,meson-s4-pwm",
+		.data = &pwm_s4_data
+	},
 	{},
 };
 MODULE_DEVICE_TABLE(of, meson_pwm_matches);
@@ -493,6 +515,14 @@ static int meson_pwm_init_channels(struct meson_pwm *meson)
 	for (i = 0; i < meson->chip.npwm; i++) {
 		struct meson_pwm_channel *channel = &meson->channels[i];
 
+		if (meson->data->ext_clk) {
+			snprintf(name, sizeof(name), "clkin%u", i);
+			channel->clk = devm_clk_get(dev, name);
+			if (IS_ERR(channel->clk))
+				return PTR_ERR(channel->clk);
+			continue;
+		}
+
 		snprintf(name, sizeof(name), "%s#mux%u", dev_name(dev), i);
 
 		init.name = name;
-- 
2.40.0