On Tue, Nov. 1, 2022, 1:43 p.m, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote: >On Tue, 01 Nov 2022, "Lee, Shawn C" <shawn.c.lee@xxxxxxxxx> wrote: >> On Tuesday, November 1, 2022 5:53 PM, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote: >>>On Mon, 24 Oct 2022, Lee Shawn C <shawn.c.lee@xxxxxxxxx> wrote: >>>> A panel power off cycle delay always append before turn eDP on. >>>> Driver should check last_power_on and last_backlight_off before >>>> insert this delay. If these values are the same, it means eDP was >>>> off until now and driver can bypass power off cycle delay to save >>>> some times to speed up eDP power on sequence. >>>> >>>> v2: fix commit messages >>> >>>There are more changes here than what the changelog says, but the previous review comments were not answered [1]. >>> >> >> I'm sorry that lose the question in [1]. >> >> "But someone else may have turned it off just before we were handed control, we have no idea." >> This is the situation from Ville's comment. Agree that we don't know when panel will be powered off. >> In my opinion, eDP panel should not be turned off before i915 take it over. If it was turned on or off by standard contorl (ex: modeset). >> last_power_on and last_backlight_off would not be the same. So this change should be safe. > >I think it's pretty much a hard requirement we respect the panel delays >at i915 probe. If we don't know, we don't know, and we can't make >assumptions. > >If the goal is to speed up boot, you should ensure 1) the pre-os >enables the display, and 2) i915 can take over the display without a >modeset and a panel power cycle. > After boot into kernel. It seems there are two cases we will see. 1) If eDP display did not enable at pre-os stage, this patch can save power cycle time. 2) If eDP display was enabled at pre-os, because of cdclk was setting to max freq always. i915 driver will trigger modeset to reduce cdclk freq and run power off/on cycle. At this case power cycle delay will not be ignored. So this patch can only benefit at case #1 (eDP did not enable at pre-os stage). And it is what we need. :) Best regards, Shawn > >BR, >Jani. > > >> >> Best regards, >> Shawn >> >>> >>>BR, >>>Jani. >>> >>> >>>[1] https://lore.kernel.org/r/Y1afUdAwfVTACJoK@xxxxxxxxx >>> >>>> >>>> Cc: Shankar Uma <uma.shankar@xxxxxxxxx> >>>> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> >>>> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >>>> Signed-off-by: Lee Shawn C <shawn.c.lee@xxxxxxxxx> >>>> --- >>>> drivers/gpu/drm/i915/display/intel_pps.c | 9 ++++++++- >>>> 1 file changed, 8 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/gpu/drm/i915/display/intel_pps.c >>>> b/drivers/gpu/drm/i915/display/intel_pps.c >>>> index 21944f5bf3a8..290473ec70d5 100644 >>>> --- a/drivers/gpu/drm/i915/display/intel_pps.c >>>> +++ b/drivers/gpu/drm/i915/display/intel_pps.c >>>> @@ -509,6 +509,13 @@ static void wait_panel_power_cycle(struct intel_dp *intel_dp) >>>> ktime_t panel_power_on_time; >>>> s64 panel_power_off_duration; >>>> >>>> + /* When last_power_on equal to last_backlight_off, it means driver did not >>>> + * turn on or off eDP panel so far. So we can bypass power cycle delay to >>>> + * save some times here. >>>> + */ >>>> + if (intel_dp->pps.last_power_on == intel_dp->pps.last_backlight_off) >>>> + return; >>>> + >>>> drm_dbg_kms(&i915->drm, "Wait for panel power cycle\n"); >>>> >>>> /* take the difference of current time and panel power off time >>>> @@ >>>> -1100,7 +1107,7 @@ static void pps_init_timestamps(struct intel_dp >>>> *intel_dp) { >>>> intel_dp->pps.panel_power_off_time = ktime_get_boottime(); >>>> intel_dp->pps.last_power_on = jiffies; >>>> - intel_dp->pps.last_backlight_off = jiffies; >>>> + intel_dp->pps.last_backlight_off = intel_dp->pps.last_power_on; >>>> } >>>> >>>> static void >>> >>>-- >>>Jani Nikula, Intel Open Source Graphics Center
