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pwm: imx: Remove ipg clock and enable per clock when required 

The use of the ipg clock was introduced with commit 7b27c160c6 ("pwm:
i.MX: fix clock lookup"). In the commit message it was claimed that the
ipg clock is enabled for register accesses. This is true for the
->config() callback, but not for the ->set_enable() callback. Given that
the ipg clock is not consistently enabled for all register accesses we
can assume that either it is not required at all or that the current
code does not work. Remove the ipg clock code for now so that it's no
longer in the way of refactoring the driver.

On the other hand, the i.MX 7 IP requires the peripheral clock to be
enabled before accessing its registers. Since ->config() can be called
when the PWM is disabled (in which case, the peripheral clock is also
disabled), we need to surround the imx->config() with
clk_prepare_enable(per_clk)/clk_disable_unprepare(per_clk) calls.

Note that the driver was working fine for the i.MX 7 IP so far because
the ipg and peripheral clock use the same hardware clock gate, which
guaranteed peripheral clock activation even when ->config() was called
when the PWM was disabled.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Tested-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
hifive-unleashed-5.1
Sascha Hauer 2017-01-29 22:54:06 +01:00 committed by Thierry Reding
parent ae2520540c
commit 9fb27fac39
1 changed files with 2 additions and 10 deletions
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12
drivers/pwm/pwm-imx.c
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@ -49,7 +49,6 @@
struct imx_chip {
struct clk *clk_per;
struct clk *clk_ipg;
void __iomem *mmio_base;
@ -206,13 +205,13 @@ static int imx_pwm_config(struct pwm_chip *chip,
struct imx_chip *imx = to_imx_chip(chip);
int ret;
ret = clk_prepare_enable(imx->clk_ipg);
ret = clk_prepare_enable(imx->clk_per);
if (ret)
return ret;
ret = imx->config(chip, pwm, duty_ns, period_ns);
clk_disable_unprepare(imx->clk_ipg);
clk_disable_unprepare(imx->clk_per);
return ret;
}
@ -293,13 +292,6 @@ static int imx_pwm_probe(struct platform_device *pdev)
return PTR_ERR(imx->clk_per);
}
imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
if (IS_ERR(imx->clk_ipg)) {
dev_err(&pdev->dev, "getting ipg clock failed with %ld\n",
PTR_ERR(imx->clk_ipg));
return PTR_ERR(imx->clk_ipg);
}
imx->chip.ops = &imx_pwm_ops;
imx->chip.dev = &pdev->dev;
imx->chip.base = -1;