Re: [PATCH 6/6] drm/i915: set the backlight panel delays registers to 1

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jan 17, 2014 at 02:57:42PM +0100, Daniel Vetter wrote:
> On Thu, Dec 19, 2013 at 09:39:12AM -0800, Jesse Barnes wrote:
> > On Thu, 19 Dec 2013 14:29:44 -0200
> > Paulo Zanoni <przanoni@gmail.com> wrote:
> > 
> > > From: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > > 
> > > Because we already do the wait in software: see
> > > ironlake_wait_backlight_on and ironlake_edp_wait_backlight_off.
> > > 
> > > For the "backlight on" delay, even BSpec says we need to program 0x1
> > > to PP_ON_DELAYS 12:0.
> > > 
> > > For the "backlight off" delay, if we don't do the same thing, when we
> > > call ironlake_wait_panel_off we'll end up waiting for the it again.
> > > 
> > > On my machine the off delay is 200ms, so we save this amount of time
> > > whenever we disable the panel (e.g, suspend).
> > > 
> > > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_dp.c | 13 ++++++++++---
> > >  1 file changed, 10 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > > index 69d8f1c..90ff059 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > @@ -3535,10 +3535,17 @@ intel_dp_init_panel_power_sequencer_registers(struct drm_device *dev,
> > >  		pp_div_reg = VLV_PIPE_PP_DIVISOR(pipe);
> > >  	}
> > >  
> > > -	/* And finally store the new values in the power sequencer. */
> > > +	/*
> > > +	 * And finally store the new values in the power sequencer. The
> > > +	 * backlight delays are set to 1 because we do manual waits on them. For
> > > +	 * T8, even BSpec recommends doing it. For T9, if we don't do this,
> > > +	 * we'll end up waiting for the backlight off delay twice: once when we
> > > +	 * do the manual sleep, and once when we disable the panel and wait for
> > > +	 * the PP_STATUS bit to become zero.
> > > +	 */
> > >  	pp_on = (seq->t1_t3 << PANEL_POWER_UP_DELAY_SHIFT) |
> > > -		(seq->t8 << PANEL_LIGHT_ON_DELAY_SHIFT);
> > > -	pp_off = (seq->t9 << PANEL_LIGHT_OFF_DELAY_SHIFT) |
> > > +		(1 << PANEL_LIGHT_ON_DELAY_SHIFT);
> > > +	pp_off = (1 << PANEL_LIGHT_OFF_DELAY_SHIFT) |
> > >  		 (seq->t10 << PANEL_POWER_DOWN_DELAY_SHIFT);
> > >  	/* Compute the divisor for the pp clock, simply match the Bspec
> > >  	 * formula. */
> > 
> > Yay!
> > 
> > Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> 
> I'll wait with this one until the updated version of patch 3 is finalized,
> but I've meanwhile pulled in patches 4&5.

Paulo convinced me that this is save already, so merged to dinq.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch