Commit 2cb5cd90 authored Feb 10, 2020 by Uwe Kleine-König Committed by Thierry Reding Mar 30, 2020

pwm: imx27: Ensure clocks being on iff the PWM is on



Up to now the .probe() function didn't enable clocks and relied on the
core to call the .get_state() callback to have the clock running. The
latter enabled the needed clocks and kept them running if the PWM wass
enabled.

This only works correctly if the .get_state() callback is called exactly
once and this single call happens before unused clocks are disabled by
the clk core.

The former wasn't true for a short period while commit 01ccf903
("pwm: Let pwm_get_state() return the last implemented state") applied
and not reverted yet and might become wrong in the future.

The latter isn't true any more since commit cfc4c189 ("pwm: Read
initial hardware state at request time") which results in a running PWM
being stopped at boot time if for example the consumer lives in a kernel
module that is only loaded after the clk core disabled unused clocks.

So ensure .probe() is left with the clocks on if the PWM is running and
.get_state() disables everything it enabled.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

parent 4563654f

drivers/pwm/pwm-imx27.c

+12 −2

Original line number	Diff line number	Diff line
		@@ -171,7 +171,6 @@ static void pwm_imx27_get_state(struct pwm_chip *chip,
		tmp = NSEC_PER_SEC * (u64)(val);
		state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);

		if (!state->enabled)
		pwm_imx27_clk_disable_unprepare(imx);
		}

		@@ -307,6 +306,8 @@ MODULE_DEVICE_TABLE(of, pwm_imx27_dt_ids);
		static int pwm_imx27_probe(struct platform_device *pdev)
		{
		struct pwm_imx27_chip *imx;
		int ret;
		u32 pwmcr;

		imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL);
		if (imx == NULL)
		@@ -349,6 +350,15 @@ static int pwm_imx27_probe(struct platform_device *pdev)
		if (IS_ERR(imx->mmio_base))
		return PTR_ERR(imx->mmio_base);

		ret = pwm_imx27_clk_prepare_enable(imx);
		if (ret)
		return ret;

		/* keep clks on if pwm is running */
		pwmcr = readl(imx->mmio_base + MX3_PWMCR);
		if (!(pwmcr & MX3_PWMCR_EN))
		pwm_imx27_clk_disable_unprepare(imx);

		return pwmchip_add(&imx->chip);
		}

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