[PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[clinton.a.taylor]

From: Clint Taylor <clinton.a.taylor@intel.com>

Backlight on delay uses PWM enable time to seperate PWM to
backlight enable assert. Previous time difference used timing
from VDD enable which occur several seconds before resulting
in PWM starting 5ms after backlight enable. Changes to backlight
 duty cycle take affect at the end of the current PWM cycle.
Measured time for the PWM cycle is 5ms. 5 additional ms must be
added to the backlight_on_delay to get correct VBT timing of
PWM to backlight enable assert.

V2: Rebase to Jani Nikula backlight power patch 1/4

Change-Id: I2982f9785d92e8d64c04ca25c8bd4c5d1dc8067c
Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 6 ++++--
 drivers/gpu/drm/i915/intel_drv.h | 1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index d8baf60..aed923b 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1141,7 +1141,7 @@ static void wait_panel_power_cycle(struct intel_dp *intel_dp)
 
 static void wait_backlight_on(struct intel_dp *intel_dp)
 {
-	wait_remaining_ms_from_jiffies(intel_dp->last_power_on,
+	wait_remaining_ms_from_jiffies(intel_dp->last_backlight_on,
 				       intel_dp->backlight_on_delay);
 }
 
@@ -1418,6 +1418,7 @@ void intel_edp_backlight_on(struct intel_dp *intel_dp)
 	DRM_DEBUG_KMS("\n");
 
 	intel_panel_enable_backlight(intel_dp->attached_connector);
+	intel_dp->last_backlight_on = jiffies;
 	_intel_edp_backlight_on(intel_dp);
 }
 
@@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
 	assign_final(t11_t12);
 #undef assign_final
 
+#define PWM_CYCLE_DELAY 5
 #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
 	intel_dp->panel_power_up_delay = get_delay(t1_t3);
-	intel_dp->backlight_on_delay = get_delay(t8);
+	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
 	intel_dp->backlight_off_delay = get_delay(t9);
 	intel_dp->panel_power_down_delay = get_delay(t10);
 	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3abc915..ad6fcc1 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -556,6 +556,7 @@ struct intel_dp {
 	bool want_panel_vdd;
 	unsigned long last_power_cycle;
 	unsigned long last_power_on;
+	unsigned long last_backlight_on;
 	unsigned long last_backlight_off;
 
 	struct notifier_block edp_notifier;
-- 
1.8.3.2

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Ville Syrjälä]

On Mon, Aug 18, 2014 at 01:48:35PM -0700, clinton.a.taylor@intel.com wrote:
> From: Clint Taylor <clinton.a.taylor@intel.com>
> 
> Backlight on delay uses PWM enable time to seperate PWM to
> backlight enable assert. Previous time difference used timing
> from VDD enable which occur several seconds before resulting
> in PWM starting 5ms after backlight enable. Changes to backlight
>  duty cycle take affect at the end of the current PWM cycle.
> Measured time for the PWM cycle is 5ms. 5 additional ms must be
> added to the backlight_on_delay to get correct VBT timing of
> PWM to backlight enable assert.
> 
> V2: Rebase to Jani Nikula backlight power patch 1/4
> 
> Change-Id: I2982f9785d92e8d64c04ca25c8bd4c5d1dc8067c
> Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 6 ++++--
>  drivers/gpu/drm/i915/intel_drv.h | 1 +
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index d8baf60..aed923b 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1141,7 +1141,7 @@ static void wait_panel_power_cycle(struct intel_dp *intel_dp)
>  
>  static void wait_backlight_on(struct intel_dp *intel_dp)
>  {
> -	wait_remaining_ms_from_jiffies(intel_dp->last_power_on,
> +	wait_remaining_ms_from_jiffies(intel_dp->last_backlight_on,
>  				       intel_dp->backlight_on_delay);
>  }
>  
> @@ -1418,6 +1418,7 @@ void intel_edp_backlight_on(struct intel_dp *intel_dp)
>  	DRM_DEBUG_KMS("\n");
>  
>  	intel_panel_enable_backlight(intel_dp->attached_connector);
> +	intel_dp->last_backlight_on = jiffies;

Seems to me we should just have a msleep(PWM_CYCLE_DELAY) here since
(assuming I understood correctly) only the PWM cycle time is important
between these two steps, and the "t8" (vbt spec says t7 actually) is
relevant only from end of link training to backlight on.

Hmm, no actually your idea might be better since on VLV/CHV we turn the
pipe on after link training, and I assume t7/t8 should really start
counting from the pipe on on those platforms. So I guess the most
appropriate solution might be somehting like

 {
   intel_dp->last_backlight_on = jiffies;
   intel_panel_enable_backlight(intel_dp->attached_connector);
   msleep(POWER_CYCLE_DELAY);
   _intel_edp_backlight_on(intel_dp);
 }

But I'm not sure the distinction makes any difference since
intel_panel_enable_backlight() shouldn't take a significant amount of
time, and msleep() is itself rather inaccurate.

So I guess your approach is the simplest option here.

>  	_intel_edp_backlight_on(intel_dp);
>  }
>  
> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
>  	assign_final(t11_t12);
>  #undef assign_final
>  
> +#define PWM_CYCLE_DELAY 5

Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
cycle here is exactly. Just one full period of the signal?

Also would be nice to have a comment in the code explaining what this is
and why we need to add it to the delay.

>  #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
>  	intel_dp->panel_power_up_delay = get_delay(t1_t3);
> -	intel_dp->backlight_on_delay = get_delay(t8);
> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
>  	intel_dp->backlight_off_delay = get_delay(t9);
>  	intel_dp->panel_power_down_delay = get_delay(t10);
>  	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 3abc915..ad6fcc1 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -556,6 +556,7 @@ struct intel_dp {
>  	bool want_panel_vdd;
>  	unsigned long last_power_cycle;
>  	unsigned long last_power_on;
> +	unsigned long last_backlight_on;
>  	unsigned long last_backlight_off;
>  
>  	struct notifier_block edp_notifier;
> -- 
> 1.8.3.2
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Clint Taylor]

On 08/20/2014 04:23 AM, Ville Syrjälä wrote:
> On Mon, Aug 18, 2014 at 01:48:35PM -0700, clinton.a.taylor@intel.com wrote:
>> From: Clint Taylor <clinton.a.taylor@intel.com>
>>
>> Backlight on delay uses PWM enable time to seperate PWM to
>> backlight enable assert. Previous time difference used timing
>> from VDD enable which occur several seconds before resulting
>> in PWM starting 5ms after backlight enable. Changes to backlight
>>   duty cycle take affect at the end of the current PWM cycle.
>> Measured time for the PWM cycle is 5ms. 5 additional ms must be
>> added to the backlight_on_delay to get correct VBT timing of
>> PWM to backlight enable assert.
>>
>> V2: Rebase to Jani Nikula backlight power patch 1/4
>>
>> Change-Id: I2982f9785d92e8d64c04ca25c8bd4c5d1dc8067c
>> Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_dp.c  | 6 ++++--
>>   drivers/gpu/drm/i915/intel_drv.h | 1 +
>>   2 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index d8baf60..aed923b 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -1141,7 +1141,7 @@ static void wait_panel_power_cycle(struct intel_dp *intel_dp)
>>
>>   static void wait_backlight_on(struct intel_dp *intel_dp)
>>   {
>> -	wait_remaining_ms_from_jiffies(intel_dp->last_power_on,
>> +	wait_remaining_ms_from_jiffies(intel_dp->last_backlight_on,
>>   				       intel_dp->backlight_on_delay);
>>   }
>>
>> @@ -1418,6 +1418,7 @@ void intel_edp_backlight_on(struct intel_dp *intel_dp)
>>   	DRM_DEBUG_KMS("\n");
>>
>>   	intel_panel_enable_backlight(intel_dp->attached_connector);
>> +	intel_dp->last_backlight_on = jiffies;
>
> Seems to me we should just have a msleep(PWM_CYCLE_DELAY) here since
> (assuming I understood correctly) only the PWM cycle time is important
> between these two steps, and the "t8" (vbt spec says t7 actually) is
> relevant only from end of link training to backlight on.
>

The driver has overloaded both T8 and T9 VBT timing entries. The eDP 
specification really doesn't have timing data defined for this 
requirement, but the panel manufacturers have it in their panel 
specification and they use various names like (Te, t17, etc...) for this 
delay.

> Hmm, no actually your idea might be better since on VLV/CHV we turn the
> pipe on after link training, and I assume t7/t8 should really start
> counting from the pipe on on those platforms. So I guess the most
> appropriate solution might be somehting like
>
>   {
>     intel_dp->last_backlight_on = jiffies;
>     intel_panel_enable_backlight(intel_dp->attached_connector);
>     msleep(POWER_CYCLE_DELAY);
>     _intel_edp_backlight_on(intel_dp);
>   }
>
> But I'm not sure the distinction makes any difference since
> intel_panel_enable_backlight() shouldn't take a significant amount of
> time, and msleep() is itself rather inaccurate.
>

There is also a need to add this delay when turning off the PWM enable 
bit through intel_panel_disable_backlight(). If the PWM enable bit is 
turned off while the PWM signal is high then the signal remains high. If 
the bit is turned off when the signal is low the PWM will remain low. 
Since we don't know the current state of the PWM signal we must set the 
duty_cycle to 0, wait PWM_CYCLE_DELAY, and then turn off the enable bit.

Actually it might be better if we never turn off the PWM enable bit in 
intel_panel_disable_backlight() and we just use the duty cycle register 
to control the PWM.

> So I guess your approach is the simplest option here.
>
>>   	_intel_edp_backlight_on(intel_dp);
>>   }
>>
>> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
>>   	assign_final(t11_t12);
>>   #undef assign_final
>>
>> +#define PWM_CYCLE_DELAY 5
>
> Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
> cycle here is exactly. Just one full period of the signal?
>

The PWM cycle in this case turns out to be 1 full cycle of the PWM 
waveform though it depends on which display core clock (128 or 
25Mhz(S0ix) is being used. Since we only care about the minimum elapsed 
time to meet the panel specification a value of 5ms will work even 
though more or less PWM cycles would take place before the BL_ENABLE is 
asserted. I would prefer not to add complexity to switch between panel 
timings for normal and S0ix display clock modes. How often does the 
backlight get enabled while in S0ix?

> Also would be nice to have a comment in the code explaining what this is
> and why we need to add it to the delay.

Sure, As you may have noticed in other patches I really like comments.

>
>>   #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
>>   	intel_dp->panel_power_up_delay = get_delay(t1_t3);
>> -	intel_dp->backlight_on_delay = get_delay(t8);
>> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
>>   	intel_dp->backlight_off_delay = get_delay(t9);
>>   	intel_dp->panel_power_down_delay = get_delay(t10);
>>   	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>> index 3abc915..ad6fcc1 100644
>> --- a/drivers/gpu/drm/i915/intel_drv.h
>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>> @@ -556,6 +556,7 @@ struct intel_dp {
>>   	bool want_panel_vdd;
>>   	unsigned long last_power_cycle;
>>   	unsigned long last_power_on;
>> +	unsigned long last_backlight_on;
>>   	unsigned long last_backlight_off;
>>
>>   	struct notifier_block edp_notifier;
>> --
>> 1.8.3.2
>>
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Ville Syrjälä]

On Thu, Aug 21, 2014 at 10:23:43AM -0700, Clint Taylor wrote:
> On 08/20/2014 04:23 AM, Ville Syrjälä wrote:
> > On Mon, Aug 18, 2014 at 01:48:35PM -0700, clinton.a.taylor@intel.com wrote:
> >> From: Clint Taylor <clinton.a.taylor@intel.com>
> >>
> >> Backlight on delay uses PWM enable time to seperate PWM to
> >> backlight enable assert. Previous time difference used timing
> >> from VDD enable which occur several seconds before resulting
> >> in PWM starting 5ms after backlight enable. Changes to backlight
> >>   duty cycle take affect at the end of the current PWM cycle.
> >> Measured time for the PWM cycle is 5ms. 5 additional ms must be
> >> added to the backlight_on_delay to get correct VBT timing of
> >> PWM to backlight enable assert.
> >>
> >> V2: Rebase to Jani Nikula backlight power patch 1/4
> >>
> >> Change-Id: I2982f9785d92e8d64c04ca25c8bd4c5d1dc8067c
> >> Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
> >> ---
> >>   drivers/gpu/drm/i915/intel_dp.c  | 6 ++++--
> >>   drivers/gpu/drm/i915/intel_drv.h | 1 +
> >>   2 files changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> >> index d8baf60..aed923b 100644
> >> --- a/drivers/gpu/drm/i915/intel_dp.c
> >> +++ b/drivers/gpu/drm/i915/intel_dp.c
> >> @@ -1141,7 +1141,7 @@ static void wait_panel_power_cycle(struct intel_dp *intel_dp)
> >>
> >>   static void wait_backlight_on(struct intel_dp *intel_dp)
> >>   {
> >> -	wait_remaining_ms_from_jiffies(intel_dp->last_power_on,
> >> +	wait_remaining_ms_from_jiffies(intel_dp->last_backlight_on,
> >>   				       intel_dp->backlight_on_delay);
> >>   }
> >>
> >> @@ -1418,6 +1418,7 @@ void intel_edp_backlight_on(struct intel_dp *intel_dp)
> >>   	DRM_DEBUG_KMS("\n");
> >>
> >>   	intel_panel_enable_backlight(intel_dp->attached_connector);
> >> +	intel_dp->last_backlight_on = jiffies;
> >
> > Seems to me we should just have a msleep(PWM_CYCLE_DELAY) here since
> > (assuming I understood correctly) only the PWM cycle time is important
> > between these two steps, and the "t8" (vbt spec says t7 actually) is
> > relevant only from end of link training to backlight on.
> >
> 
> The driver has overloaded both T8 and T9 VBT timing entries. The eDP 
> specification really doesn't have timing data defined for this 
> requirement, but the panel manufacturers have it in their panel 
> specification and they use various names like (Te, t17, etc...) for this 
> delay.
> 
> > Hmm, no actually your idea might be better since on VLV/CHV we turn the
> > pipe on after link training, and I assume t7/t8 should really start
> > counting from the pipe on on those platforms. So I guess the most
> > appropriate solution might be somehting like
> >
> >   {
> >     intel_dp->last_backlight_on = jiffies;
> >     intel_panel_enable_backlight(intel_dp->attached_connector);
> >     msleep(POWER_CYCLE_DELAY);
> >     _intel_edp_backlight_on(intel_dp);
> >   }
> >
> > But I'm not sure the distinction makes any difference since
> > intel_panel_enable_backlight() shouldn't take a significant amount of
> > time, and msleep() is itself rather inaccurate.
> >
> 
> There is also a need to add this delay when turning off the PWM enable 
> bit through intel_panel_disable_backlight(). If the PWM enable bit is 
> turned off while the PWM signal is high then the signal remains high. If 
> the bit is turned off when the signal is low the PWM will remain low. 
> Since we don't know the current state of the PWM signal we must set the 
> duty_cycle to 0, wait PWM_CYCLE_DELAY, and then turn off the enable bit.
> 
> Actually it might be better if we never turn off the PWM enable bit in 
> intel_panel_disable_backlight() and we just use the duty cycle register 
> to control the PWM.
> 
> > So I guess your approach is the simplest option here.
> >
> >>   	_intel_edp_backlight_on(intel_dp);
> >>   }
> >>
> >> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
> >>   	assign_final(t11_t12);
> >>   #undef assign_final
> >>
> >> +#define PWM_CYCLE_DELAY 5
> >
> > Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
> > cycle here is exactly. Just one full period of the signal?
> >
> 
> The PWM cycle in this case turns out to be 1 full cycle of the PWM 
> waveform though it depends on which display core clock (128 or 
> 25Mhz(S0ix) is being used. Since we only care about the minimum elapsed 
> time to meet the panel specification a value of 5ms will work even 
> though more or less PWM cycles would take place before the BL_ENABLE is 
> asserted. I would prefer not to add complexity to switch between panel 
> timings for normal and S0ix display clock modes. How often does the 
> backlight get enabled while in S0ix?

I'm not sure how this could even be a problem for s0ix. The driver would
be suspended by the time we enter s0ix.

I'm more worried about other platforms that may have different pwm
cycle. So it seems to me that we should calculate the pwm cycle as
DIV_ROUND_UP(1000, intel_hrawclk()), assuming it's hrawclk instead of
cdclk that's used (which is the impression I get from the docs).

> 
> > Also would be nice to have a comment in the code explaining what this is
> > and why we need to add it to the delay.
> 
> Sure, As you may have noticed in other patches I really like comments.
> 
> >
> >>   #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
> >>   	intel_dp->panel_power_up_delay = get_delay(t1_t3);
> >> -	intel_dp->backlight_on_delay = get_delay(t8);
> >> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
> >>   	intel_dp->backlight_off_delay = get_delay(t9);
> >>   	intel_dp->panel_power_down_delay = get_delay(t10);
> >>   	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
> >> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> >> index 3abc915..ad6fcc1 100644
> >> --- a/drivers/gpu/drm/i915/intel_drv.h
> >> +++ b/drivers/gpu/drm/i915/intel_drv.h
> >> @@ -556,6 +556,7 @@ struct intel_dp {
> >>   	bool want_panel_vdd;
> >>   	unsigned long last_power_cycle;
> >>   	unsigned long last_power_on;
> >> +	unsigned long last_backlight_on;
> >>   	unsigned long last_backlight_off;
> >>
> >>   	struct notifier_block edp_notifier;
> >> --
> >> 1.8.3.2
> >>
> >> _______________________________________________
> >> Intel-gfx mailing list
> >> Intel-gfx@lists.freedesktop.org
> >> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >

-- 
Ville Syrjälä
Intel OTC

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Jani Nikula]

+Art

On Thu, 21 Aug 2014, Clint Taylor <clinton.a.taylor@intel.com> wrote:
> There is also a need to add this delay when turning off the PWM enable 
> bit through intel_panel_disable_backlight(). If the PWM enable bit is 
> turned off while the PWM signal is high then the signal remains high. If 
> the bit is turned off when the signal is low the PWM will remain low. 
> Since we don't know the current state of the PWM signal we must set the 
> duty_cycle to 0, wait PWM_CYCLE_DELAY, and then turn off the enable bit.

[citation needed]

Really, I want this in the specs if this is true.

> Actually it might be better if we never turn off the PWM enable bit in 
> intel_panel_disable_backlight() and we just use the duty cycle register 
> to control the PWM.

Art, any feedback on these two?

BR,
Jani.


>
>> So I guess your approach is the simplest option here.
>>
>>>   	_intel_edp_backlight_on(intel_dp);
>>>   }
>>>
>>> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
>>>   	assign_final(t11_t12);
>>>   #undef assign_final
>>>
>>> +#define PWM_CYCLE_DELAY 5
>>
>> Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
>> cycle here is exactly. Just one full period of the signal?
>>
>
> The PWM cycle in this case turns out to be 1 full cycle of the PWM 
> waveform though it depends on which display core clock (128 or 
> 25Mhz(S0ix) is being used. Since we only care about the minimum elapsed 
> time to meet the panel specification a value of 5ms will work even 
> though more or less PWM cycles would take place before the BL_ENABLE is 
> asserted. I would prefer not to add complexity to switch between panel 
> timings for normal and S0ix display clock modes. How often does the 
> backlight get enabled while in S0ix?
>
>> Also would be nice to have a comment in the code explaining what this is
>> and why we need to add it to the delay.
>
> Sure, As you may have noticed in other patches I really like comments.
>
>>
>>>   #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
>>>   	intel_dp->panel_power_up_delay = get_delay(t1_t3);
>>> -	intel_dp->backlight_on_delay = get_delay(t8);
>>> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
>>>   	intel_dp->backlight_off_delay = get_delay(t9);
>>>   	intel_dp->panel_power_down_delay = get_delay(t10);
>>>   	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
>>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>>> index 3abc915..ad6fcc1 100644
>>> --- a/drivers/gpu/drm/i915/intel_drv.h
>>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>>> @@ -556,6 +556,7 @@ struct intel_dp {
>>>   	bool want_panel_vdd;
>>>   	unsigned long last_power_cycle;
>>>   	unsigned long last_power_on;
>>> +	unsigned long last_backlight_on;
>>>   	unsigned long last_backlight_off;
>>>
>>>   	struct notifier_block edp_notifier;
>>> --
>>> 1.8.3.2
>>>
>>> _______________________________________________
>>> Intel-gfx mailing list
>>> Intel-gfx@lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Runyan, Arthur J]

I'll check it out.  I haven't heard any complaint about this before, but it may be one of those things that started back on i745 and never got documented. 

-----Original Message-----
From: Jani Nikula [mailto:jani.nikula@linux.intel.com] 
Sent: Friday, August 22, 2014 6:07 AM
To: Taylor, Clinton A; Ville Syrjälä; Runyan, Arthur J
Cc: Intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert


+Art

On Thu, 21 Aug 2014, Clint Taylor <clinton.a.taylor@intel.com> wrote:
> There is also a need to add this delay when turning off the PWM enable 
> bit through intel_panel_disable_backlight(). If the PWM enable bit is 
> turned off while the PWM signal is high then the signal remains high. If 
> the bit is turned off when the signal is low the PWM will remain low. 
> Since we don't know the current state of the PWM signal we must set the 
> duty_cycle to 0, wait PWM_CYCLE_DELAY, and then turn off the enable bit.

[citation needed]

Really, I want this in the specs if this is true.

> Actually it might be better if we never turn off the PWM enable bit in 
> intel_panel_disable_backlight() and we just use the duty cycle register 
> to control the PWM.

Art, any feedback on these two?

BR,
Jani.


>
>> So I guess your approach is the simplest option here.
>>
>>>   	_intel_edp_backlight_on(intel_dp);
>>>   }
>>>
>>> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
>>>   	assign_final(t11_t12);
>>>   #undef assign_final
>>>
>>> +#define PWM_CYCLE_DELAY 5
>>
>> Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
>> cycle here is exactly. Just one full period of the signal?
>>
>
> The PWM cycle in this case turns out to be 1 full cycle of the PWM 
> waveform though it depends on which display core clock (128 or 
> 25Mhz(S0ix) is being used. Since we only care about the minimum elapsed 
> time to meet the panel specification a value of 5ms will work even 
> though more or less PWM cycles would take place before the BL_ENABLE is 
> asserted. I would prefer not to add complexity to switch between panel 
> timings for normal and S0ix display clock modes. How often does the 
> backlight get enabled while in S0ix?
>
>> Also would be nice to have a comment in the code explaining what this is
>> and why we need to add it to the delay.
>
> Sure, As you may have noticed in other patches I really like comments.
>
>>
>>>   #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
>>>   	intel_dp->panel_power_up_delay = get_delay(t1_t3);
>>> -	intel_dp->backlight_on_delay = get_delay(t8);
>>> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
>>>   	intel_dp->backlight_off_delay = get_delay(t9);
>>>   	intel_dp->panel_power_down_delay = get_delay(t10);
>>>   	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
>>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>>> index 3abc915..ad6fcc1 100644
>>> --- a/drivers/gpu/drm/i915/intel_drv.h
>>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>>> @@ -556,6 +556,7 @@ struct intel_dp {
>>>   	bool want_panel_vdd;
>>>   	unsigned long last_power_cycle;
>>>   	unsigned long last_power_on;
>>> +	unsigned long last_backlight_on;
>>>   	unsigned long last_backlight_off;
>>>
>>>   	struct notifier_block edp_notifier;
>>> --
>>> 1.8.3.2
>>>
>>> _______________________________________________
>>> Intel-gfx mailing list
>>> Intel-gfx@lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Daniel Vetter]

On Fri, Aug 22, 2014 at 05:12:25PM +0000, Runyan, Arthur J wrote:
> I'll check it out.  I haven't heard any complaint about this before, but
> it may be one of those things that started back on i745 and never got
> documented. 

Only i855 and later started to have native lvds with all the surrounding
stuff, before there's only bridge chips that did all the magic. So won't
be quite _that_ old ;-)

Cheers, Daniel

> 
> -----Original Message-----
> From: Jani Nikula [mailto:jani.nikula@linux.intel.com] 
> Sent: Friday, August 22, 2014 6:07 AM
> To: Taylor, Clinton A; Ville Syrjälä; Runyan, Arthur J
> Cc: Intel-gfx@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert
> 
> 
> +Art
> 
> On Thu, 21 Aug 2014, Clint Taylor <clinton.a.taylor@intel.com> wrote:
> > There is also a need to add this delay when turning off the PWM enable 
> > bit through intel_panel_disable_backlight(). If the PWM enable bit is 
> > turned off while the PWM signal is high then the signal remains high. If 
> > the bit is turned off when the signal is low the PWM will remain low. 
> > Since we don't know the current state of the PWM signal we must set the 
> > duty_cycle to 0, wait PWM_CYCLE_DELAY, and then turn off the enable bit.
> 
> [citation needed]
> 
> Really, I want this in the specs if this is true.
> 
> > Actually it might be better if we never turn off the PWM enable bit in 
> > intel_panel_disable_backlight() and we just use the duty cycle register 
> > to control the PWM.
> 
> Art, any feedback on these two?
> 
> BR,
> Jani.
> 
> 
> >
> >> So I guess your approach is the simplest option here.
> >>
> >>>   	_intel_edp_backlight_on(intel_dp);
> >>>   }
> >>>
> >>> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
> >>>   	assign_final(t11_t12);
> >>>   #undef assign_final
> >>>
> >>> +#define PWM_CYCLE_DELAY 5
> >>
> >> Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
> >> cycle here is exactly. Just one full period of the signal?
> >>
> >
> > The PWM cycle in this case turns out to be 1 full cycle of the PWM 
> > waveform though it depends on which display core clock (128 or 
> > 25Mhz(S0ix) is being used. Since we only care about the minimum elapsed 
> > time to meet the panel specification a value of 5ms will work even 
> > though more or less PWM cycles would take place before the BL_ENABLE is 
> > asserted. I would prefer not to add complexity to switch between panel 
> > timings for normal and S0ix display clock modes. How often does the 
> > backlight get enabled while in S0ix?
> >
> >> Also would be nice to have a comment in the code explaining what this is
> >> and why we need to add it to the delay.
> >
> > Sure, As you may have noticed in other patches I really like comments.
> >
> >>
> >>>   #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
> >>>   	intel_dp->panel_power_up_delay = get_delay(t1_t3);
> >>> -	intel_dp->backlight_on_delay = get_delay(t8);
> >>> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
> >>>   	intel_dp->backlight_off_delay = get_delay(t9);
> >>>   	intel_dp->panel_power_down_delay = get_delay(t10);
> >>>   	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
> >>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> >>> index 3abc915..ad6fcc1 100644
> >>> --- a/drivers/gpu/drm/i915/intel_drv.h
> >>> +++ b/drivers/gpu/drm/i915/intel_drv.h
> >>> @@ -556,6 +556,7 @@ struct intel_dp {
> >>>   	bool want_panel_vdd;
> >>>   	unsigned long last_power_cycle;
> >>>   	unsigned long last_power_on;
> >>> +	unsigned long last_backlight_on;
> >>>   	unsigned long last_backlight_off;
> >>>
> >>>   	struct notifier_block edp_notifier;
> >>> --
> >>> 1.8.3.2
> >>>
> >>> _______________________________________________
> >>> Intel-gfx mailing list
> >>> Intel-gfx@lists.freedesktop.org
> >>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >>
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Runyan, Arthur J]

:-)   We pulled most of the mobile functions from the bridge chip into the main chip, so that same backlight code might well have been there.
>From sandybridge onwards I see that hardware will override the PWM signal to inactive (0 if backlight polarity is active high, 1 if active low) when PWM is disabled (PWM control bit 31 = 0).  I don't have anything older than sandybridge to look at, and of course there could always be some hidden bug that prevents the override from kicking in. 

-----Original Message-----
From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch] On Behalf Of Daniel Vetter
Sent: Tuesday, August 26, 2014 2:52 AM
To: Runyan, Arthur J
Cc: Jani Nikula; Taylor, Clinton A; Ville Syrjälä; Intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

On Fri, Aug 22, 2014 at 05:12:25PM +0000, Runyan, Arthur J wrote:
> I'll check it out.  I haven't heard any complaint about this before, but
> it may be one of those things that started back on i745 and never got
> documented. 

Only i855 and later started to have native lvds with all the surrounding
stuff, before there's only bridge chips that did all the magic. So won't
be quite _that_ old ;-)

Cheers, Daniel

> 
> -----Original Message-----
> From: Jani Nikula [mailto:jani.nikula@linux.intel.com] 
> Sent: Friday, August 22, 2014 6:07 AM
> To: Taylor, Clinton A; Ville Syrjälä; Runyan, Arthur J
> Cc: Intel-gfx@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert
> 
> 
> +Art
> 
> On Thu, 21 Aug 2014, Clint Taylor <clinton.a.taylor@intel.com> wrote:
> > There is also a need to add this delay when turning off the PWM enable 
> > bit through intel_panel_disable_backlight(). If the PWM enable bit is 
> > turned off while the PWM signal is high then the signal remains high. If 
> > the bit is turned off when the signal is low the PWM will remain low. 
> > Since we don't know the current state of the PWM signal we must set the 
> > duty_cycle to 0, wait PWM_CYCLE_DELAY, and then turn off the enable bit.
> 
> [citation needed]
> 
> Really, I want this in the specs if this is true.
> 
> > Actually it might be better if we never turn off the PWM enable bit in 
> > intel_panel_disable_backlight() and we just use the duty cycle register 
> > to control the PWM.
> 
> Art, any feedback on these two?
> 
> BR,
> Jani.
> 
> 
> >
> >> So I guess your approach is the simplest option here.
> >>
> >>>   	_intel_edp_backlight_on(intel_dp);
> >>>   }
> >>>
> >>> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
> >>>   	assign_final(t11_t12);
> >>>   #undef assign_final
> >>>
> >>> +#define PWM_CYCLE_DELAY 5
> >>
> >> Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
> >> cycle here is exactly. Just one full period of the signal?
> >>
> >
> > The PWM cycle in this case turns out to be 1 full cycle of the PWM 
> > waveform though it depends on which display core clock (128 or 
> > 25Mhz(S0ix) is being used. Since we only care about the minimum elapsed 
> > time to meet the panel specification a value of 5ms will work even 
> > though more or less PWM cycles would take place before the BL_ENABLE is 
> > asserted. I would prefer not to add complexity to switch between panel 
> > timings for normal and S0ix display clock modes. How often does the 
> > backlight get enabled while in S0ix?
> >
> >> Also would be nice to have a comment in the code explaining what this is
> >> and why we need to add it to the delay.
> >
> > Sure, As you may have noticed in other patches I really like comments.
> >
> >>
> >>>   #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
> >>>   	intel_dp->panel_power_up_delay = get_delay(t1_t3);
> >>> -	intel_dp->backlight_on_delay = get_delay(t8);
> >>> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
> >>>   	intel_dp->backlight_off_delay = get_delay(t9);
> >>>   	intel_dp->panel_power_down_delay = get_delay(t10);
> >>>   	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
> >>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> >>> index 3abc915..ad6fcc1 100644
> >>> --- a/drivers/gpu/drm/i915/intel_drv.h
> >>> +++ b/drivers/gpu/drm/i915/intel_drv.h
> >>> @@ -556,6 +556,7 @@ struct intel_dp {
> >>>   	bool want_panel_vdd;
> >>>   	unsigned long last_power_cycle;
> >>>   	unsigned long last_power_on;
> >>> +	unsigned long last_backlight_on;
> >>>   	unsigned long last_backlight_off;
> >>>
> >>>   	struct notifier_block edp_notifier;
> >>> --
> >>> 1.8.3.2
> >>>
> >>> _______________________________________________
> >>> Intel-gfx mailing list
> >>> Intel-gfx@lists.freedesktop.org
> >>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >>
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Clint Taylor]

On 08/27/2014 01:54 PM, Runyan, Arthur J wrote:
> :-)   We pulled most of the mobile functions from the bridge chip into the main chip, so that same backlight code might well have been there.
>  From sandybridge onwards I see that hardware will override the PWM signal to inactive (0 if backlight polarity is active high, 1 if active low) when PWM is disabled (PWM control bit 31 = 0).  I don't have anything older than sandybridge to look at, and of course there could always be some hidden bug that prevents the override from kicking in.
>

Just enabling/disabling the PWM control bit will reproduce the issue on 
VLV. I have not tested on other platforms.

Clint

> -----Original Message-----
> From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch] On Behalf Of Daniel Vetter
> Sent: Tuesday, August 26, 2014 2:52 AM
> To: Runyan, Arthur J
> Cc: Jani Nikula; Taylor, Clinton A; Ville Syrjälä; Intel-gfx@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert
>
> On Fri, Aug 22, 2014 at 05:12:25PM +0000, Runyan, Arthur J wrote:
>> I'll check it out.  I haven't heard any complaint about this before, but
>> it may be one of those things that started back on i745 and never got
>> documented.
>
> Only i855 and later started to have native lvds with all the surrounding
> stuff, before there's only bridge chips that did all the magic. So won't
> be quite _that_ old ;-)
>
> Cheers, Daniel
>
>>
>> -----Original Message-----
>> From: Jani Nikula [mailto:jani.nikula@linux.intel.com]
>> Sent: Friday, August 22, 2014 6:07 AM
>> To: Taylor, Clinton A; Ville Syrjälä; Runyan, Arthur J
>> Cc: Intel-gfx@lists.freedesktop.org
>> Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert
>>
>>
>> +Art
>>
>> On Thu, 21 Aug 2014, Clint Taylor <clinton.a.taylor@intel.com> wrote:
>>> There is also a need to add this delay when turning off the PWM enable
>>> bit through intel_panel_disable_backlight(). If the PWM enable bit is
>>> turned off while the PWM signal is high then the signal remains high. If
>>> the bit is turned off when the signal is low the PWM will remain low.
>>> Since we don't know the current state of the PWM signal we must set the
>>> duty_cycle to 0, wait PWM_CYCLE_DELAY, and then turn off the enable bit.
>>
>> [citation needed]
>>
>> Really, I want this in the specs if this is true.
>>
>>> Actually it might be better if we never turn off the PWM enable bit in
>>> intel_panel_disable_backlight() and we just use the duty cycle register
>>> to control the PWM.
>>
>> Art, any feedback on these two?
>>
>> BR,
>> Jani.
>>
>>
>>>
>>>> So I guess your approach is the simplest option here.
>>>>
>>>>>    	_intel_edp_backlight_on(intel_dp);
>>>>>    }
>>>>>
>>>>> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
>>>>>    	assign_final(t11_t12);
>>>>>    #undef assign_final
>>>>>
>>>>> +#define PWM_CYCLE_DELAY 5
>>>>
>>>> Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
>>>> cycle here is exactly. Just one full period of the signal?
>>>>
>>>
>>> The PWM cycle in this case turns out to be 1 full cycle of the PWM
>>> waveform though it depends on which display core clock (128 or
>>> 25Mhz(S0ix) is being used. Since we only care about the minimum elapsed
>>> time to meet the panel specification a value of 5ms will work even
>>> though more or less PWM cycles would take place before the BL_ENABLE is
>>> asserted. I would prefer not to add complexity to switch between panel
>>> timings for normal and S0ix display clock modes. How often does the
>>> backlight get enabled while in S0ix?
>>>
>>>> Also would be nice to have a comment in the code explaining what this is
>>>> and why we need to add it to the delay.
>>>
>>> Sure, As you may have noticed in other patches I really like comments.
>>>
>>>>
>>>>>    #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
>>>>>    	intel_dp->panel_power_up_delay = get_delay(t1_t3);
>>>>> -	intel_dp->backlight_on_delay = get_delay(t8);
>>>>> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
>>>>>    	intel_dp->backlight_off_delay = get_delay(t9);
>>>>>    	intel_dp->panel_power_down_delay = get_delay(t10);
>>>>>    	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
>>>>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>>>>> index 3abc915..ad6fcc1 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_drv.h
>>>>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>>>>> @@ -556,6 +556,7 @@ struct intel_dp {
>>>>>    	bool want_panel_vdd;
>>>>>    	unsigned long last_power_cycle;
>>>>>    	unsigned long last_power_on;
>>>>> +	unsigned long last_backlight_on;
>>>>>    	unsigned long last_backlight_off;
>>>>>
>>>>>    	struct notifier_block edp_notifier;
>>>>> --
>>>>> 1.8.3.2
>>>>>
>>>>> _______________________________________________
>>>>> Intel-gfx mailing list
>>>>> Intel-gfx@lists.freedesktop.org
>>>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>>>
>>>
>>> _______________________________________________
>>> Intel-gfx mailing list
>>> Intel-gfx@lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>
>> --
>> Jani Nikula, Intel Open Source Technology Center
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Runyan, Arthur J]

VLV is a whole different can of worms.  Some parts of display are from before sanybridge, and it may have some special muxing on the backlight pins.  I won't be able to give any feedback on how hardware behaves there.

-----Original Message-----
From: Taylor, Clinton A 
Sent: Tuesday, September 02, 2014 5:27 PM
To: Runyan, Arthur J; Daniel Vetter
Cc: Jani Nikula; Ville Syrjälä; Intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

On 08/27/2014 01:54 PM, Runyan, Arthur J wrote:
> :-)   We pulled most of the mobile functions from the bridge chip into the main chip, so that same backlight code might well have been there.
>  From sandybridge onwards I see that hardware will override the PWM signal to inactive (0 if backlight polarity is active high, 1 if active low) when PWM is disabled (PWM control bit 31 = 0).  I don't have anything older than sandybridge to look at, and of course there could always be some hidden bug that prevents the override from kicking in.
>

Just enabling/disabling the PWM control bit will reproduce the issue on 
VLV. I have not tested on other platforms.

Clint

> -----Original Message-----
> From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch] On Behalf Of Daniel Vetter
> Sent: Tuesday, August 26, 2014 2:52 AM
> To: Runyan, Arthur J
> Cc: Jani Nikula; Taylor, Clinton A; Ville Syrjälä; Intel-gfx@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert
>
> On Fri, Aug 22, 2014 at 05:12:25PM +0000, Runyan, Arthur J wrote:
>> I'll check it out.  I haven't heard any complaint about this before, but
>> it may be one of those things that started back on i745 and never got
>> documented.
>
> Only i855 and later started to have native lvds with all the surrounding
> stuff, before there's only bridge chips that did all the magic. So won't
> be quite _that_ old ;-)
>
> Cheers, Daniel
>
>>
>> -----Original Message-----
>> From: Jani Nikula [mailto:jani.nikula@linux.intel.com]
>> Sent: Friday, August 22, 2014 6:07 AM
>> To: Taylor, Clinton A; Ville Syrjälä; Runyan, Arthur J
>> Cc: Intel-gfx@lists.freedesktop.org
>> Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert
>>
>>
>> +Art
>>
>> On Thu, 21 Aug 2014, Clint Taylor <clinton.a.taylor@intel.com> wrote:
>>> There is also a need to add this delay when turning off the PWM enable
>>> bit through intel_panel_disable_backlight(). If the PWM enable bit is
>>> turned off while the PWM signal is high then the signal remains high. If
>>> the bit is turned off when the signal is low the PWM will remain low.
>>> Since we don't know the current state of the PWM signal we must set the
>>> duty_cycle to 0, wait PWM_CYCLE_DELAY, and then turn off the enable bit.
>>
>> [citation needed]
>>
>> Really, I want this in the specs if this is true.
>>
>>> Actually it might be better if we never turn off the PWM enable bit in
>>> intel_panel_disable_backlight() and we just use the duty cycle register
>>> to control the PWM.
>>
>> Art, any feedback on these two?
>>
>> BR,
>> Jani.
>>
>>
>>>
>>>> So I guess your approach is the simplest option here.
>>>>
>>>>>    	_intel_edp_backlight_on(intel_dp);
>>>>>    }
>>>>>
>>>>> @@ -4256,9 +4257,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
>>>>>    	assign_final(t11_t12);
>>>>>    #undef assign_final
>>>>>
>>>>> +#define PWM_CYCLE_DELAY 5
>>>>
>>>> Shoduln't this be calculated from the PWM frequqncy? Not sure what a PWM
>>>> cycle here is exactly. Just one full period of the signal?
>>>>
>>>
>>> The PWM cycle in this case turns out to be 1 full cycle of the PWM
>>> waveform though it depends on which display core clock (128 or
>>> 25Mhz(S0ix) is being used. Since we only care about the minimum elapsed
>>> time to meet the panel specification a value of 5ms will work even
>>> though more or less PWM cycles would take place before the BL_ENABLE is
>>> asserted. I would prefer not to add complexity to switch between panel
>>> timings for normal and S0ix display clock modes. How often does the
>>> backlight get enabled while in S0ix?
>>>
>>>> Also would be nice to have a comment in the code explaining what this is
>>>> and why we need to add it to the delay.
>>>
>>> Sure, As you may have noticed in other patches I really like comments.
>>>
>>>>
>>>>>    #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
>>>>>    	intel_dp->panel_power_up_delay = get_delay(t1_t3);
>>>>> -	intel_dp->backlight_on_delay = get_delay(t8);
>>>>> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
>>>>>    	intel_dp->backlight_off_delay = get_delay(t9);
>>>>>    	intel_dp->panel_power_down_delay = get_delay(t10);
>>>>>    	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
>>>>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>>>>> index 3abc915..ad6fcc1 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_drv.h
>>>>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>>>>> @@ -556,6 +556,7 @@ struct intel_dp {
>>>>>    	bool want_panel_vdd;
>>>>>    	unsigned long last_power_cycle;
>>>>>    	unsigned long last_power_on;
>>>>> +	unsigned long last_backlight_on;
>>>>>    	unsigned long last_backlight_off;
>>>>>
>>>>>    	struct notifier_block edp_notifier;
>>>>> --
>>>>> 1.8.3.2
>>>>>
>>>>> _______________________________________________
>>>>> Intel-gfx mailing list
>>>>> Intel-gfx@lists.freedesktop.org
>>>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>>>
>>>
>>> _______________________________________________
>>> Intel-gfx mailing list
>>> Intel-gfx@lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>
>> --
>> Jani Nikula, Intel Open Source Technology Center
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>

[PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[clinton.a.taylor]

From: Clint Taylor <clinton.a.taylor@intel.com>

Backlight on delay uses PWM enable time to seperate PWM to
backlight enable assert. Previous time difference used timing
from VDD enable which occur several seconds before resulting
in PWM starting 5ms after backlight enable. Changes to backlight
 duty cycle take affect at the end of the current PWM cycle.
Measured time for the PWM cycle is 5ms. 5 additional ms must be
added to the backlight_on_delay to get correct VBT timing of
PWM to backlight enable assert.

Change-Id: I484999a597fd84dacf4cf99a168ec9ba4bb6ff11
Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 6 ++++--
 drivers/gpu/drm/i915/intel_drv.h | 1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index e5ada4f..c59ccdb 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1141,7 +1141,7 @@ static void wait_panel_power_cycle(struct intel_dp *intel_dp)
 
 static void wait_backlight_on(struct intel_dp *intel_dp)
 {
-	wait_remaining_ms_from_jiffies(intel_dp->last_power_on,
+	wait_remaining_ms_from_jiffies(intel_dp->last_backlight_on,
 				       intel_dp->backlight_on_delay);
 }
 
@@ -1398,6 +1398,7 @@ void intel_edp_backlight_on(struct intel_dp *intel_dp)
 	DRM_DEBUG_KMS("\n");
 
 	intel_panel_enable_backlight(intel_dp->attached_connector);
+	intel_dp->last_backlight_on = jiffies;
 
 	/*
 	 * If we enable the backlight right away following a panel power
@@ -4243,9 +4244,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
 	assign_final(t11_t12);
 #undef assign_final
 
+#define PWM_CYCLE_DELAY 5
 #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
 	intel_dp->panel_power_up_delay = get_delay(t1_t3);
-	intel_dp->backlight_on_delay = get_delay(t8);
+	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
 	intel_dp->backlight_off_delay = get_delay(t9);
 	intel_dp->panel_power_down_delay = get_delay(t10);
 	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3abc915..ad6fcc1 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -556,6 +556,7 @@ struct intel_dp {
 	bool want_panel_vdd;
 	unsigned long last_power_cycle;
 	unsigned long last_power_on;
+	unsigned long last_backlight_on;
 	unsigned long last_backlight_off;
 
 	struct notifier_block edp_notifier;
-- 
1.8.3.2

Re: [PATCH] drm/i915/dp: Backlight PWM enable before BL Enable assert

[Jani Nikula]

On Fri, 15 Aug 2014, clinton.a.taylor@intel.com wrote:
> From: Clint Taylor <clinton.a.taylor@intel.com>
>
> Backlight on delay uses PWM enable time to seperate PWM to
> backlight enable assert. Previous time difference used timing
> from VDD enable which occur several seconds before resulting
> in PWM starting 5ms after backlight enable. Changes to backlight
>  duty cycle take affect at the end of the current PWM cycle.
> Measured time for the PWM cycle is 5ms. 5 additional ms must be
> added to the backlight_on_delay to get correct VBT timing of
> PWM to backlight enable assert.

The patch seems sane, but I'd like you to rebase this on top of patch
1/4 of my backlight series [1] so I can queue them both to
drm-intel-fixes. Then we'll have fewer conflicts with the rest of the
backlight series going forward.

Hint hint, I'd also appreciate review of my backlight series. ;)

BR,
Jani.


[1] http://mid.gmane.org/e7a47b50ed0f25cafdc26711fc09561ea8af3b81.1407849872.git.jani.nikula@intel.com


>
> Change-Id: I484999a597fd84dacf4cf99a168ec9ba4bb6ff11
> Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 6 ++++--
>  drivers/gpu/drm/i915/intel_drv.h | 1 +
>  2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index e5ada4f..c59ccdb 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1141,7 +1141,7 @@ static void wait_panel_power_cycle(struct intel_dp *intel_dp)
>  
>  static void wait_backlight_on(struct intel_dp *intel_dp)
>  {
> -	wait_remaining_ms_from_jiffies(intel_dp->last_power_on,
> +	wait_remaining_ms_from_jiffies(intel_dp->last_backlight_on,
>  				       intel_dp->backlight_on_delay);
>  }
>  
> @@ -1398,6 +1398,7 @@ void intel_edp_backlight_on(struct intel_dp *intel_dp)
>  	DRM_DEBUG_KMS("\n");
>  
>  	intel_panel_enable_backlight(intel_dp->attached_connector);
> +	intel_dp->last_backlight_on = jiffies;
>  
>  	/*
>  	 * If we enable the backlight right away following a panel power
> @@ -4243,9 +4244,10 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
>  	assign_final(t11_t12);
>  #undef assign_final
>  
> +#define PWM_CYCLE_DELAY 5
>  #define get_delay(field)	(DIV_ROUND_UP(final.field, 10))
>  	intel_dp->panel_power_up_delay = get_delay(t1_t3);
> -	intel_dp->backlight_on_delay = get_delay(t8);
> +	intel_dp->backlight_on_delay = get_delay(t8) + PWM_CYCLE_DELAY;
>  	intel_dp->backlight_off_delay = get_delay(t9);
>  	intel_dp->panel_power_down_delay = get_delay(t10);
>  	intel_dp->panel_power_cycle_delay = get_delay(t11_t12);
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 3abc915..ad6fcc1 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -556,6 +556,7 @@ struct intel_dp {
>  	bool want_panel_vdd;
>  	unsigned long last_power_cycle;
>  	unsigned long last_power_on;
> +	unsigned long last_backlight_on;
>  	unsigned long last_backlight_off;
>  
>  	struct notifier_block edp_notifier;
> -- 
> 1.8.3.2
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center