Sebastian,

On Wed, Aug 12, 2015 at 04:21:16PM +0200, Sebastian Hesselbarth wrote:

On 08/12/2015 03:51 PM, Antoine Tenart wrote:

quoted

Add a PWM controller driver for the Marvell Berlin SoCs. This PWM
controller has 4 channels.

Signed-off-by: Antoine Tenart <redacted>

nice rework, but...

[...]

quoted

diff --git a/drivers/pwm/pwm-berlin.c b/drivers/pwm/pwm-berlin.c
new file mode 100644
index 000000000000..f89e25ea5c6d
--- /dev/null
+++ b/drivers/pwm/pwm-berlin.c

@@ -0,0 +1,227 @@

[...]

quoted

+#define BERLIN_PWM_ENABLE		BIT(0)
+#define BERLIN_PWM_DISABLE		0x0

I'd drop BERLIN_PWM_DISABLE and use reg & ~BERLIN_PWM_ENABLE below.
Even if there are no more writable bits in that register, IMHO it
is good practice to affect as little bits as possible.

Sure.

[...]

quoted

+/* prescaler table: {1, 4, 8, 16, 64, 256, 1024, 4096} */
+static const u32 prescaler_diff_table[] = {
+	1, 4, 2, 2, 4, 4, 4, 4,
+};
+
+static int berlin_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			     int duty_ns, int period_ns)
+{
+	struct berlin_pwm_chip *berlin_chip = to_berlin_pwm_chip(chip);
+	int ret, prescale = 0;
+	u32 val, duty, period;
+	u64 cycles;
+
+	cycles = clk_get_rate(berlin_chip->clk);
+	cycles *= period_ns;
+	do_div(cycles, NSEC_PER_SEC);
+
+	while (cycles > BERLIN_PWM_MAX_TCNT)
+		do_div(cycles, prescaler_diff_table[++prescale]);
+
+	if (cycles > BERLIN_PWM_MAX_TCNT)
+		return -EINVAL;

Does my idea actually work? Did you test it with some different
pwm frequencies?

I tested, and it worked well with different pwm frequencies!

quoted

+	period = cycles;
+	cycles *= duty_ns;
+	do_div(cycles, period_ns);
+	duty = cycles;
+
+	ret = clk_prepare_enable(berlin_chip->clk);
+	if (ret)
+		return ret;

Hmm. I understand that this may be required as the pwm framework
calls .pwm_config before .pwm_enable, but...

quoted

+
+	spin_lock(&berlin_chip->lock);
+
+	val = berlin_pwm_readl(berlin_chip, pwm->hwpwm, BERLIN_PWM_CONTROL);
+	val &= ~BERLIN_PWM_PRESCALE_MASK;
+	val |= prescale;
+	berlin_pwm_writel(val, berlin_chip, pwm->hwpwm, BERLIN_PWM_CONTROL);
+
+	berlin_pwm_writel(duty, berlin_chip, pwm->hwpwm, BERLIN_PWM_DUTY);
+	berlin_pwm_writel(period, berlin_chip, pwm->hwpwm, BERLIN_PWM_TCNT);
+
+	spin_unlock(&berlin_chip->lock);
+
+	clk_disable_unprepare(berlin_chip->clk);

Are you sure that register contents are retained after disabling the
clock? I understand that cfg_clk is the _ip_ input clock and pwm gets
derived from it.

Actually, since cfg_clk seems to be an important, internal SoC clock
I'd say to clk_prepare_enable() in _probe() before reading any
registers and clk_disable_unprepare() on _remove() (see below).

I'll update.

Internal low-frequency clocks don't consume that much power that it
is worth the pain ;)

quoted

+	return 0;
+}
+
+static int berlin_pwm_set_polarity(struct pwm_chip *chip,
+				   struct pwm_device *pwm,
+				   enum pwm_polarity polarity)
+{
+	struct berlin_pwm_chip *berlin_chip = to_berlin_pwm_chip(chip);
+	int ret;
+	u32 val;
+
+	ret = clk_prepare_enable(berlin_chip->clk);
+	if (ret)
+		return ret;

These would become unnecessary then.

quoted

+	spin_lock(&berlin_chip->lock);
+
+	val = berlin_pwm_readl(berlin_chip, pwm->hwpwm, BERLIN_PWM_CONTROL);
+
+	if (polarity == PWM_POLARITY_NORMAL)
+		val &= ~BERLIN_PWM_INVERT_POLARITY;
+	else
+		val |= BERLIN_PWM_INVERT_POLARITY;
+
+	berlin_pwm_writel(val, berlin_chip, pwm->hwpwm, BERLIN_PWM_CONTROL);
+
+	spin_unlock(&berlin_chip->lock);
+
+	clk_disable_unprepare(berlin_chip->clk);

ditto.

quoted

+	return 0;
+}
+
+static int berlin_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct berlin_pwm_chip *berlin_chip = to_berlin_pwm_chip(chip);
+	int ret;
+
+	ret = clk_prepare_enable(berlin_chip->clk);
+	if (ret)
+		return ret;

ditto.

quoted

+	spin_lock(&berlin_chip->lock);
+	berlin_pwm_writel(BERLIN_PWM_ENABLE, berlin_chip, pwm->hwpwm, BERLIN_PWM_EN);
+	spin_unlock(&berlin_chip->lock);
+
+	return 0;
+}
+
+static void berlin_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct berlin_pwm_chip *berlin_chip = to_berlin_pwm_chip(chip);
+
+	spin_lock(&berlin_chip->lock);
+	berlin_pwm_writel(BERLIN_PWM_DISABLE, berlin_chip, pwm->hwpwm, BERLIN_PWM_EN);
+	spin_unlock(&berlin_chip->lock);
+
+	clk_disable_unprepare(berlin_chip->clk);

ditto.

quoted

+}
+
+static const struct pwm_ops berlin_pwm_ops = {
+	.config = berlin_pwm_config,
+	.set_polarity = berlin_pwm_set_polarity,
+	.enable = berlin_pwm_enable,
+	.disable = berlin_pwm_disable,
+	.owner = THIS_MODULE,
+};
+
+static const struct of_device_id berlin_pwm_match[] = {
+	{ .compatible = "marvell,berlin-pwm" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, berlin_pwm_match);
+
+static int berlin_pwm_probe(struct platform_device *pdev)
+{
+	struct berlin_pwm_chip *pwm;
+	struct resource *res;
+	int ret;
+
+	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
+	if (!pwm)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	pwm->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(pwm->base))
+		return PTR_ERR(pwm->base);
+
+	pwm->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(pwm->clk))
+		return PTR_ERR(pwm->clk);
+
+	pwm->chip.dev = &pdev->dev;
+	pwm->chip.ops = &berlin_pwm_ops;
+	pwm->chip.base = -1;
+	pwm->chip.npwm = 4;
+	pwm->chip.can_sleep = true;
+	pwm->chip.of_xlate = of_pwm_xlate_with_flags;
+	pwm->chip.of_pwm_n_cells = 3;
+
+	spin_lock_init(&pwm->lock);

add clk_prepare_enable() before adding the pwmchip...

quoted

+	ret = pwmchip_add(&pwm->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Failed to add PWM chip: %d\n", ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, pwm);
+
+	return 0;
+}
+
+static int berlin_pwm_remove(struct platform_device *pdev)
+{
+	struct berlin_pwm_chip *pwm = platform_get_drvdata(pdev);
+
+	return pwmchip_remove(&pwm->chip);

... and clk_disable_unprepare after removing it.

Besides the comments, for Berlin you get my

Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>

Thanks!

Antoine

quoted

+}
+
+static struct platform_driver berlin_pwm_driver = {
+	.probe	= berlin_pwm_probe,
+	.remove	= berlin_pwm_remove,
+	.driver	= {
+		.name	= "berlin-pwm",
+		.of_match_table = berlin_pwm_match,
+	},
+};
+module_platform_driver(berlin_pwm_driver);
+
+MODULE_AUTHOR("Antoine Tenart [off-list ref]");
+MODULE_DESCRIPTION("Marvell Berlin PWM driver");
+MODULE_LICENSE("GPL v2");

-- 
Antoine T?nart, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com