Messages in this thread | | | Date | Mon, 21 Jun 2021 14:08:17 +0530 | From | rajeevny@codeauro ... | Subject | Re: [v7 1/5] drm/panel: add basic DP AUX backlight support |
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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@codeaurora.org> >> Reviewed-by: Douglas Anderson <dianders@chromium.org> >> Reviewed-by: Lyude Paul <lyude@redhat.com> >> --- >> >> (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
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