* Does the i915 VBT tell us if a panel is an OLED panel? @ 2019-10-10 12:46 Hans de Goede 2019-10-10 13:35 ` Jani Nikula 0 siblings, 1 reply; 4+ messages in thread From: Hans de Goede @ 2019-10-10 12:46 UTC (permalink / raw) To: Jani Nikula; +Cc: Christian Kellner, Intel-gfx Hi Jani, During plumbers I had some discussions with Daniel about supporting OLED screens. Userspace may need to know that a panel is OLED for 2 reasons: 1) To avoid screen burn-in 2) OLED screens do not have a classic backlight, so in some cases some sort of brightness/contrast emulation through gamma tables may be necessary to still allow the user to control the brightness. The idea we've discussed is to add a property on the drm_connector (details to be filled in) which indicates that the panel is an OLED panel. This has lead to the question: "how do we know the panel is OLED"? Do you know if this info is coded into the VBT somewhere? Regards, Hans _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Does the i915 VBT tell us if a panel is an OLED panel? 2019-10-10 12:46 Does the i915 VBT tell us if a panel is an OLED panel? Hans de Goede @ 2019-10-10 13:35 ` Jani Nikula 2019-10-11 19:30 ` Sean Paul 0 siblings, 1 reply; 4+ messages in thread From: Jani Nikula @ 2019-10-10 13:35 UTC (permalink / raw) To: Hans de Goede; +Cc: Christian Kellner, Intel-gfx On Thu, 10 Oct 2019, Hans de Goede <hdegoede@redhat.com> wrote: > Hi Jani, > > During plumbers I had some discussions with Daniel about supporting > OLED screens. Userspace may need to know that a panel is OLED for 2 > reasons: > > 1) To avoid screen burn-in > 2) OLED screens do not have a classic backlight, so in some cases > some sort of brightness/contrast emulation through gamma tables may > be necessary to still allow the user to control the brightness. I'd think most OLED displays have a native way to control brightness. Some eDP panels can use the eDP PWM pin to control brightness, although it does not directly drive an actual backlight, and some others use the eDP standard DPCD brightness control methods. Similarly, OLED DSI displays have DCS commands for this. Often I've seen various content adaptive brightness settings combined with the OLED brightness control, so it can be more power efficient than using gamma. > The idea we've discussed is to add a property on the drm_connector > (details to be filled in) which indicates that the panel is an OLED > panel. > > This has lead to the question: "how do we know the panel is OLED"? > > Do you know if this info is coded into the VBT somewhere? Not AFAICT. But there is the indication of the brightness control method, and one option is the eDP AUX interface. I fathom it's entirely possible for panels to use the eDP AUX interface for controlling an LCD backlight, so this does not directly translate to OLED. However, the DisplayID spec has Display Device Data block (0x0c) that contains Display Device Technology byte, including a value for Organic LED/OEL. I haven't actually checked any OLED displays if they have this or not, and we don't currently parse it in drm, but this seems like a better option than VBT. Moreover, this is usable also for regular DP, which should be as important as eDP for the burn-in avoidance. BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Does the i915 VBT tell us if a panel is an OLED panel? 2019-10-10 13:35 ` Jani Nikula @ 2019-10-11 19:30 ` Sean Paul 2019-10-14 8:12 ` Jani Nikula 0 siblings, 1 reply; 4+ messages in thread From: Sean Paul @ 2019-10-11 19:30 UTC (permalink / raw) To: Jani Nikula; +Cc: Christian Kellner, Intel-gfx On Thu, Oct 10, 2019 at 04:35:56PM +0300, Jani Nikula wrote: > On Thu, 10 Oct 2019, Hans de Goede <hdegoede@redhat.com> wrote: > > Hi Jani, > > > > During plumbers I had some discussions with Daniel about supporting > > OLED screens. Userspace may need to know that a panel is OLED for 2 > > reasons: > > > > 1) To avoid screen burn-in > > 2) OLED screens do not have a classic backlight, so in some cases > > some sort of brightness/contrast emulation through gamma tables may > > be necessary to still allow the user to control the brightness. > > I'd think most OLED displays have a native way to control > brightness. Some eDP panels can use the eDP PWM pin to control > brightness, although it does not directly drive an actual backlight, and > some others use the eDP standard DPCD brightness control > methods. Similarly, OLED DSI displays have DCS commands for this. > > Often I've seen various content adaptive brightness settings combined > with the OLED brightness control, so it can be more power efficient than > using gamma. > > > The idea we've discussed is to add a property on the drm_connector > > (details to be filled in) which indicates that the panel is an OLED > > panel. > > > > This has lead to the question: "how do we know the panel is OLED"? > > > > Do you know if this info is coded into the VBT somewhere? > > Not AFAICT. But there is the indication of the brightness control > method, and one option is the eDP AUX interface. I fathom it's entirely > possible for panels to use the eDP AUX interface for controlling an LCD > backlight, so this does not directly translate to OLED. > > However, the DisplayID spec has Display Device Data block (0x0c) that > contains Display Device Technology byte, including a value for Organic > LED/OEL. I haven't actually checked any OLED displays if they have this > or not, and we don't currently parse it in drm, but this seems like a > better option than VBT. Moreover, this is usable also for regular DP, > which should be as important as eDP for the burn-in avoidance. One datapoint: I have an eDP OLED panel and it does not seem to have DisplayID extensions. Sean > > BR, > Jani. > > > -- > Jani Nikula, Intel Open Source Graphics Center -- Sean Paul, Software Engineer, Google / Chromium OS _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Does the i915 VBT tell us if a panel is an OLED panel? 2019-10-11 19:30 ` Sean Paul @ 2019-10-14 8:12 ` Jani Nikula 0 siblings, 0 replies; 4+ messages in thread From: Jani Nikula @ 2019-10-14 8:12 UTC (permalink / raw) To: Sean Paul; +Cc: Christian Kellner, Intel-gfx On Fri, 11 Oct 2019, Sean Paul <sean@poorly.run> wrote: > On Thu, Oct 10, 2019 at 04:35:56PM +0300, Jani Nikula wrote: >> On Thu, 10 Oct 2019, Hans de Goede <hdegoede@redhat.com> wrote: >> > Hi Jani, >> > >> > During plumbers I had some discussions with Daniel about supporting >> > OLED screens. Userspace may need to know that a panel is OLED for 2 >> > reasons: >> > >> > 1) To avoid screen burn-in >> > 2) OLED screens do not have a classic backlight, so in some cases >> > some sort of brightness/contrast emulation through gamma tables may >> > be necessary to still allow the user to control the brightness. >> >> I'd think most OLED displays have a native way to control >> brightness. Some eDP panels can use the eDP PWM pin to control >> brightness, although it does not directly drive an actual backlight, and >> some others use the eDP standard DPCD brightness control >> methods. Similarly, OLED DSI displays have DCS commands for this. >> >> Often I've seen various content adaptive brightness settings combined >> with the OLED brightness control, so it can be more power efficient than >> using gamma. >> >> > The idea we've discussed is to add a property on the drm_connector >> > (details to be filled in) which indicates that the panel is an OLED >> > panel. >> > >> > This has lead to the question: "how do we know the panel is OLED"? >> > >> > Do you know if this info is coded into the VBT somewhere? >> >> Not AFAICT. But there is the indication of the brightness control >> method, and one option is the eDP AUX interface. I fathom it's entirely >> possible for panels to use the eDP AUX interface for controlling an LCD >> backlight, so this does not directly translate to OLED. >> >> However, the DisplayID spec has Display Device Data block (0x0c) that >> contains Display Device Technology byte, including a value for Organic >> LED/OEL. I haven't actually checked any OLED displays if they have this >> or not, and we don't currently parse it in drm, but this seems like a >> better option than VBT. Moreover, this is usable also for regular DP, >> which should be as important as eDP for the burn-in avoidance. > > One datapoint: I have an eDP OLED panel and it does not seem to have > DisplayID extensions. Does the DPCD say it supports backlight control through DP AUX? BR, Jani. > > Sean > >> >> BR, >> Jani. >> >> >> -- >> Jani Nikula, Intel Open Source Graphics Center -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-10-14 8:11 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2019-10-10 12:46 Does the i915 VBT tell us if a panel is an OLED panel? Hans de Goede 2019-10-10 13:35 ` Jani Nikula 2019-10-11 19:30 ` Sean Paul 2019-10-14 8:12 ` Jani Nikula
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