Hello Russell,

On Sun, Mar 29, 2020 at 07:22:36PM +0100, Russell King - ARM Linux admin wrote:

On Sun, Mar 29, 2020 at 08:00:56PM +0200, Uwe Kleine-König wrote:

quoted

On Sun, Mar 29, 2020 at 02:34:00PM +0100, Russell King - ARM Linux admin wrote:

quoted

On Sun, Mar 29, 2020 at 03:16:59PM +0200, Uwe Kleine-König wrote:

quoted

On Sun, Mar 29, 2020 at 11:48:09AM +0100, Russell King wrote:

quoted

diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
index fa5641615db6..ee13b11c5298 100644
--- a/drivers/gpio/gpio-mvebu.c
+++ b/drivers/gpio/gpio-mvebu.c

@@ -1132,6 +1132,9 @@ static int mvebu_gpio_probe(struct platform_device *pdev)
 	}
 
 	mvchip->clk = devm_clk_get(&pdev->dev, NULL);
+	if (mvchip->clk == ERR_PTR(-EPROBE_DEFER))
+		return -EPROBE_DEFER;
+
 	/* Not all SoCs require a clock.*/
 	if (!IS_ERR(mvchip->clk))
 		clk_prepare_enable(mvchip->clk);

I'd say the following is the right thing to do here:

	mvchip->clk = devm_clk_get_optional(...);
	if (IS_ERR(mvchip->clk))
		return ...

It's not that simple.  The clock is required for Armada 370, and is
optional for Armada 8040.

I'd say it is still the right approach here. On Armada 370 the dtb then
has a clk and on Armada 8040 it doesn't. So if with
devm_clk_get_optional() something goes wrong that's because the dtb is
wrong. And in fact the handling is even better than with your suggested
patch as every error (but EPROBE_DEFER) is ignored instead of passed to
the caller with your (and the existing) approach.

Sort of.  Every error is currently treated as "no clock", and only
later does such an error become fatal in the driver _if_ PWM is
configured into the kernel and we're running on Armada 370.  If PWM
is disabled in the kernel, or on some other SoC, then the driver
doesn't care whether getting the clock reported any kind of error.

Your proposal is to always treat any error getting the clock,
irrespective of whether there is PWM or not, as a fatal error for
the driver.

Is this clock (assuming it's available) needed for GPIO operation? If
not, I'd say the call to devm_clk_get should go into mvebu_pwm_probe().
And if yes, then use devm_clk_get_optional in mvebu_gpio_probe() and
either request it once more in mvebu_pwm_probe() (without _optional) or
test for mvchip->clk == NULL. (Or maybe just don't check and let the
driver fail when clk_get_rate(mvchip->clk) returns zero.)

That is an entirely seperate functional change.

This is still different to what you do, but it is (IMHO) cleaner and
fixes the problem you want to solve en passant.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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