[PATCH v2] gpio: zynq: initialize clock even without CONFIG_PM

[PATCH v2] gpio: zynq: initialize clock even without CONFIG_PM

[Helmut Grohne]

When the PM initialization was moved in the commit referenced below, the
code enabling the clock was removed from the probe function. On
CONFIG_PM=y kernels, this is not a problem as the pm resume hook enables
the clock, but when power management is disabled, all those pm_*
functions are noops and the clock is never enabled resulting in a
dysfunctional gpio controller.

Put the clock initialization back to support CONFIG_PM=n.

Signed-off-by: Helmut Grohne <h.grohne@intenta.de>
Fixes: 3773c195d387 ("gpio: zynq: Do PM initialization earlier to support gpio hogs")
---
 drivers/gpio/gpio-zynq.c | 7 +++++++
 1 file changed, 7 insertions(+)

Changes in v2: Rebased on 4.7-rc1.

On 06/02/2016 02:30 PM, Linus Walleij wrote:
> Sould it be tagged for stable and sent to fixes?

I already asked this question in my initial patch posting, because I am
unsure. If you deem CONFIG_PM=n and gpio-zynq a common configuration,
then the answer probably is "yes".

The patch that makes the rebase non-trivial, is 615d23f80efc ("gpio:
zynq: Fix the error path"). If you deem CONFIG_PM=y and gpio-zynq a
common configuration, then this patch likely should also go to stable.

Both of them fix regressions in 3773c195d387 ("gpio: zynq: Do PM
initialization earlier to support gpio hogs"), which was introduced in
4.4, so stable trees earlier than that don't need these patches.

Please note that this rebased patch is only compile tested, because some
required drivers broke with 4.7-rc1. If you are reluctant to apply the
patch under this condition, I can report back after fixing drivers.
Posting the updated patch anyway in case the other Helmut wants to test
it.

Helmut

diff --git a/drivers/gpio/gpio-zynq.c b/drivers/gpio/gpio-zynq.c
index 75c6355..e72794e 100644
--- a/drivers/gpio/gpio-zynq.c
+++ b/drivers/gpio/gpio-zynq.c
@@ -709,7 +709,13 @@ static int zynq_gpio_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "input clock not found.\n");
 		return PTR_ERR(gpio->clk);
 	}
+	ret = clk_prepare_enable(gpio->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "Unable to enable clock.\n");
+		return ret;
+	}
 
+	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
 	ret = pm_runtime_get_sync(&pdev->dev);
 	if (ret < 0)
@@ -747,6 +753,7 @@ err_pm_put:
 	pm_runtime_put(&pdev->dev);
 err_pm_dis:
 	pm_runtime_disable(&pdev->dev);
+	clk_disable_unprepare(gpio->clk);
 
 	return ret;
 }
-- 
2.1.4

Re: [PATCH v2] gpio: zynq: initialize clock even without CONFIG_PM

[Helmut Grohne]

On Fri, Jun 03, 2016 at 02:15:32PM +0200, Helmut Grohne wrote:
> Please note that this rebased patch is only compile tested, because some
> required drivers broke with 4.7-rc1. If you are reluctant to apply the
> patch under this condition, I can report back after fixing drivers.
> Posting the updated patch anyway in case the other Helmut wants to test
> it.

Excuse the quick followup. I gave up fixing the driver before the
weekend but then it turned out to be much easier than expected.

I now tested the patch with 4.7-rc1 (plus some out of tree drivers) on
our board both with CONFIG_PM=y and CONFIG_PM=n and confirm that it
works as expected. With CONFIG_PM=n and plain 4.7-rc1, the gpio
controller doesn't work at all.

Helmut

Re: [PATCH v2] gpio: zynq: initialize clock even without CONFIG_PM

[Linus Walleij]

On Fri, Jun 3, 2016 at 2:15 PM, Helmut Grohne <h.grohne@intenta.de> wrote:

> When the PM initialization was moved in the commit referenced below, the
> code enabling the clock was removed from the probe function. On
> CONFIG_PM=y kernels, this is not a problem as the pm resume hook enables
> the clock, but when power management is disabled, all those pm_*
> functions are noops and the clock is never enabled resulting in a
> dysfunctional gpio controller.
>
> Put the clock initialization back to support CONFIG_PM=n.
>
> Signed-off-by: Helmut Grohne <h.grohne@intenta.de>
> Fixes: 3773c195d387 ("gpio: zynq: Do PM initialization earlier to support gpio hogs")

This v2 patch applied for fixes and tagged for stable.

Yours,
Linus Walleij