From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Date: Mon, 10 Feb 2020 22:22:40 +0100
Subject: pwm: imx27: Ensure clocks being on iff the PWM is on
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Git-commit: 2cb5cd90f4cd3f819178bb47f3d1ef86ce612db7
Patch-mainline: v5.7-rc1
References: jsc#SLE-16106
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 01ccf903edd6
("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 cfc4c189bc70 ("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>
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
drivers/pwm/pwm-imx27.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c
index fb142813d455..e83c077bb7cc 100644
--- a/drivers/pwm/pwm-imx27.c
+++ b/drivers/pwm/pwm-imx27.c
@@ -171,8 +171,7 @@ 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);
+ pwm_imx27_clk_disable_unprepare(imx);
}
static void pwm_imx27_sw_reset(struct pwm_chip *chip)
@@ -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);
}