Den 11.12.2017 18.45, skrev Noralf Trønnes:
Den 11.12.2017 15.58, skrev Meghana Madhyastha:
On Mon, Dec 11, 2017 at 03:12:06PM +0100, Noralf Trønnes wrote:
Den 11.12.2017 14.17, skrev Meghana Madhyastha:
On Sat, Dec 09, 2017 at 03:09:28PM +0100, Noralf Trønnes wrote:
Den 21.10.2017 13.55, skrev Meghana Madhyastha:
Changes in v14:
- s/backlight_get/of_find_backlight/ in patch 2/3
- Change commit message in patch 3/3 from requiring to acquiring
Meghana Madhyastha (3):
drm/tinydrm: Move helper functions from tinydrm-helpers to
backlight.h
drm/tinydrm: Move tinydrm_of_find_backlight to backlight.c
drm/tinydrm: Add devres versions of of_find_backlight
I tried the patchset and this is what I got:
[ 8.057792] Unable to handle kernel paging request at virtual
address
fffffe6b
<snip>
[ 9.144181] ---[ end trace 149c05934b6a6dcc ]---
Is the reason possibly because we have omitted error checking on the
return value of backlight_enable function ?
tinydrm_enable_backlight and
tinydrm_disable_baclight do this.
Eg.
ret = backlight_update_status(backlight);
if (ret)
DRM_ERROR("Failed to enable backlight %d\n", ret);
I'm not sure, just asking whether this could be a possible reason
for the above trace.
The crash happens during probe.
I guess you'll figure this out when you get some hw to test on.
I have set up the raspberry pi and have built and boot into the
custom kernel
but I am waiting for the panel to arrive. Meanwhile, any thoughts on
error message ? Sorry for the trivial question, but I did not quite
understand the crash message and how to replicate it.
of_find_backlight() can return an error pointer (-EPROBE_DEFER):
diff --git a/drivers/video/backlight/backlight.c
b/drivers/video/backlight/backlight.c
index 4bb7bf3ee443..57370c5d51f0 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -635,8 +635,8 @@ struct backlight_device
*devm_of_find_backlight(struct device *dev)
int ret;
bd = of_find_backlight(dev);
- if (!bd)
- return NULL;
+ if (IS_ERR_OR_NULL(bd))
+ return bd;
ret = devm_add_action(dev, devm_backlight_put, bd);
if (ret) {
That solved the crash, but the backlight didn't turn on.
I had to do this as well:
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 5c441d4c049c..6f9925f10a7c 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -139,6 +139,8 @@ static inline int backlight_enable(struct
backlight_device *bd)
if (!bd)
return 0;
+ if (!bd->props.brightness)
+ bd->props.brightness = bd->props.max_brightness;
No, this is wrong, it should happen on probe, not every time it's enabled.
So maybe it should be done in of_find_backlight() or something.
I see that I'm currently doing it in tinydrm_of_find_backlight().
bd->props.power = FB_BLANK_UNBLANK;
bd->props.state &= ~BL_CORE_FBBLANK;
This is my backlight node[1]:
backlight: backlight {
compatible = "gpio-backlight";
gpios = <&gpio 18 0>; // GPIO_ACTIVE_HIGH
};
Not certain that this is the "correct" solution, but I can't use the
gpio-backlight property default-on, because that would turn on backlight
before the pipeline is enabled.
You can dry-run the driver without a panel connected, it can work
without being able to read from the controller.
Noralf.
[1]
https://github.com/notro/tinydrm/blob/master/rpi-overlays/rpi-display-overlay.dts
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