Hi Peter,
On Tue, Nov 22, 2016 at 2:41 PM, Peter Ujfalusi <peter.ujfalusi@xxxxxx> wrote:
> Move the checks to select the initial state for the backlight to a new
> function and document the checks we are doing.
This is far from a simple "move"...
> With the separate function it is going to be easier to fix or improve the
> initial power state configuration later and it is easier to read the code.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
> Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> Reviewed-by: Thierry Reding <treding@xxxxxxxxxx>
This patch (commit 7613c922315e308a in v4.11-rc1) broke the display on
r8a7740/armadillo.
> @@ -267,20 +292,16 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> pb->enable_gpio = gpio_to_desc(data->enable_gpio);
> }
>
> - if (pb->enable_gpio) {
> - /*
> - * If the driver is probed from the device tree and there is a
> - * phandle link pointing to the backlight node, it is safe to
> - * assume that another driver will enable the backlight at the
> - * appropriate time. Therefore, if it is disabled, keep it so.
> - */
> - if (node && node->phandle &&
> - gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&
> - gpiod_get_value(pb->enable_gpio) == 0)
> - initial_blank = FB_BLANK_POWERDOWN;
> - else
> - gpiod_direction_output(pb->enable_gpio, 1);
In my case, "node" points to the "/backlight" node, but phandle is NULL.
Hence before, gpiod_direction_output() was called to enable the GPIO...
> - }
> + /*
> + * If the GPIO is configured as input, change the direction to output
> + * and set the GPIO as active.
> + * Do not force the GPIO to active when it was already output as it
> + * could cause backlight flickering or we would enable the backlight too
> + * early. Leave the decision of the initial backlight state for later.
> + */
> + if (pb->enable_gpio &&
> + gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> + gpiod_direction_output(pb->enable_gpio, 1);
... while now it's no longer called, as gpiod_get_direction() returns
-EINVAL.
Indeed, r8a7740_pfc does not implement the .get_direction() callback,
so gpiod_get_direction() always returns -EINVAL, which is never equal
to GPIOF_DIR_IN.
Restoring the old behavior by changing the above test to
if (pb->enable_gpio &&
(!node || !node->phandle ||
gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN))
fixes the display for me, but leads to a more complex expression.
However, changing the test to
if (pb->enable_gpio &&
gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
also fixes the display, as an error is always different from GPIOF_DIR_OUT.
Anyone with comments or suggestions to fix this for real?
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
