Hi Sam,
On 20-06-2021 15:01, Sam Ravnborg wrote:
Hi Rajeev
On Sat, Jun 19, 2021 at 04:10:26PM +0530, Rajeev Nandan wrote:
Some panels support backlight control over DP AUX channel using
VESA's standard backlight control interface.
Using new DRM eDP backlight helpers, add support to create and
register a backlight for those panels in drm_panel to simplify
the panel drivers.
The panel driver with access to "struct drm_dp_aux" can create and
register a backlight device using following code snippet in its
probe() function:
err = drm_panel_dp_aux_backlight(panel, aux);
if (err)
return err;
IT very good to have this supported by drm_panel, so we avoid
bolierplate in various drivers.
Then drm_panel will handle backlight_(enable|disable) calls
similar to the case when drm_panel_of_backlight() is used.
Currently, we are not supporting one feature where the source
device can combine the backlight brightness levels set through
DP AUX and the BL_PWM_DIM eDP connector pin. Since it's not
required for the basic backlight controls, it can be added later.
Signed-off-by: Rajeev Nandan <rajeevny@xxxxxxxxxxxxxx>
Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
---
(no changes since v6)
Changes in v5:
- New
Changes in v6:
- Fixed ordering of memory allocation (Douglas)
- Updated word wrapping in a comment (Douglas)
drivers/gpu/drm/drm_panel.c | 108
++++++++++++++++++++++++++++++++++++++++++++
include/drm/drm_panel.h | 15 ++++--
2 files changed, 119 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index f634371..9e65342 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -26,12 +26,20 @@
#include <linux/module.h>
#include <drm/drm_crtc.h>
+#include <drm/drm_dp_helper.h>
#include <drm/drm_panel.h>
#include <drm/drm_print.h>
static DEFINE_MUTEX(panel_lock);
static LIST_HEAD(panel_list);
+struct dp_aux_backlight {
+ struct backlight_device *base;
+ struct drm_dp_aux *aux;
+ struct drm_edp_backlight_info info;
+ bool enabled;
+};
+
/**
* DOC: drm panel
*
@@ -342,6 +350,106 @@ int drm_panel_of_backlight(struct drm_panel
*panel)
return 0;
}
EXPORT_SYMBOL(drm_panel_of_backlight);
+
+static int dp_aux_backlight_update_status(struct backlight_device
*bd)
+{
+ struct dp_aux_backlight *bl = bl_get_data(bd);
+ u16 brightness = backlight_get_brightness(bd);
backlight_get_brightness() returns an int, so using u16 seems wrong.
But then drm_edp_backlight_enable() uses u16 for level - so I guess it
is OK.
We use unsigned long, int, u16 for brightness. Looks like something one
could look at one day, but today is not that day.
+ int ret = 0;
+
+ if (brightness > 0) {
Use backlight_is_blank(bd) here, as this is really what you test for.
The backlight_get_brightness() used above has the backlight_is_blank()
check and returns brightness 0 when the backlight_is_blank(bd) is true.
So, instead of calling backlight_is_blank(bd), we are checking
brightness value here.
I took the reference from pwm_backlight_update_status() of the PWM
backlight driver (drivers/video/backlight/pwm_bl.c)
Yes, we can change this _if_ condition to use backlight_is_blank(bd), as
this is an inline function, and is more meaningful.
With this, there would be one change in the behavior of
_backlight_update_status function in the following case:
- Setting brightness=0 when the backlight is not blank:
In the current case setting brightness=0 is disabling the backlight.
In the new case, setting brightness=0 will set the brightness to 0 and
will do nothing to backlight disable.
I think that should not be a problem?
I cannot see why you need the extra check on ->enabled?
Would it be sufficient to check backlight_is_blank() only?
This extra check on bl->enabled flag is added to avoid
enabling/disabling backlight again if it is already enabled/disabled.
Using this flag way can know the transition between backlight blank and
un-blank, and decide when to enable/disable the backlight.
+ if (!bl->enabled) {
+ drm_edp_backlight_enable(bl->aux, &bl->info, brightness);
+ bl->enabled = true;
+ return 0;
+ }
+ ret = drm_edp_backlight_set_level(bl->aux, &bl->info, brightness);
+ } else {
+ if (bl->enabled) {
+ drm_edp_backlight_disable(bl->aux, &bl->info);
+ bl->enabled = false;
+ }
+ }
+
+ return ret;
+}
Sam
Thanks,
Rajeev
