Re: [PATCH] drm/i915: reboot notifier delay for eDP panels

[Clint Taylor <clinton.a.taylor@intel.com>]

On 01/12/2016 05:21 AM, Ville Syrjälä wrote:
> On Mon, Jan 11, 2016 at 01:52:17PM -0800, clinton.a.taylor@intel.com wrote:
>> From: Clint Taylor <clinton.a.taylor@intel.com>
>>
>> Add reboot notifier for all platforms. This guarantees T12 delay
>> compliance during reboot cycles when pre-os enables the panel within
>> 500ms.
>>
>> Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_dp.c |   11 ++++++++---
>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 796e3d3..dbbd27a 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -126,6 +126,7 @@ static struct intel_dp *intel_attached_dp(struct drm_connector *connector)
>>   static void intel_dp_link_down(struct intel_dp *intel_dp);
>>   static bool edp_panel_vdd_on(struct intel_dp *intel_dp);
>>   static void edp_panel_vdd_off(struct intel_dp *intel_dp, bool sync);
>> +static void edp_panel_off(struct intel_dp *intel_dp);
>>   static void vlv_init_panel_power_sequencer(struct intel_dp *intel_dp);
>>   static void vlv_steal_power_sequencer(struct drm_device *dev,
>>   				      enum pipe pipe);
>> @@ -596,6 +597,10 @@ static int edp_notify_handler(struct notifier_block *this, unsigned long code,
>>   		I915_WRITE(pp_ctrl_reg, PANEL_UNLOCK_REGS | PANEL_POWER_OFF);
>>   		msleep(intel_dp->panel_power_cycle_delay);
>>   	}
>> +	else
>> +	{
>> +		edp_panel_off(intel_dp);
>> +	}
>
> I don't think that actually waits for the power cycle delay. Also
> you can't call it without having vdd already enabled unless you
> specifically want to see a WARN.
>
edp_panel_off() does wait for panel off time. This has also been 
confirmed with a scope watching vdd.

> I suppose you could just do something along these lines:
>
> if (have_panel_power || have_panel_vdd) {
Good catch. I will add the check to make sure panel power is on before 
calling edp_panel_off(). If the panel power was off I will still need to 
check to make sure it has been off for the required time.

> 	edp_panel_vdd_on
> 	edp_panel_off
> }
> wait_panel_power_cycle
>
> Also should change VLV/CHV to do it the same way.

VLV/CHV PPS handles things a little different and the existing code was 
required to prevent VDD from asserting during the reboot cycle. We 
increased the delay to MAX the VLV handler to prevent the VDD from 
asserting once the PPS cycle completed. I will test on my CHV to confirm 
the old handler is still required.

>
>>
>>   	pps_unlock(intel_dp);
>>
>> @@ -5796,10 +5801,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>>   	}
>>   	mutex_unlock(&dev->mode_config.mutex);
>>
>> -	if (IS_VALLEYVIEW(dev) || IS_CHERRYVIEW(dev)) {
>> -		intel_dp->edp_notifier.notifier_call = edp_notify_handler;
>> -		register_reboot_notifier(&intel_dp->edp_notifier);
>> +	intel_dp->edp_notifier.notifier_call = edp_notify_handler;
>> +	register_reboot_notifier(&intel_dp->edp_notifier);
>>
>> +	if (IS_VALLEYVIEW(dev) || IS_CHERRYVIEW(dev)) {
>>   		/*
>>   		 * Figure out the current pipe for the initial backlight setup.
>>   		 * If the current pipe isn't valid, try the PPS pipe, and if that
>> --
>> 1.7.9.5
>>
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>

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