Re: [Intel-gfx] [PATCH v8 6/8] drm/i915: WA for platforms with double buffered adress update enable bit

[Karthik B S <karthik.b.s@intel.com>]

On 9/15/2020 7:49 PM, Ville Syrjälä wrote:
> On Mon, Sep 14, 2020 at 11:26:31AM +0530, Karthik B S wrote:
>> In Gen 9 and Gen 10 platforms, async address update enable bit is
>> double buffered. Due to this, during the transition from async flip
>> to sync flip we have to wait until this bit is updated before continuing
>> with the normal commit for sync flip.
>>
>> Signed-off-by: Karthik B S <karthik.b.s@intel.com>
>> Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_display.c | 44 ++++++++++++++++++++
>>   1 file changed, 44 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
>> index a0c17d94daf3..b7e24dff0772 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>> @@ -15360,6 +15360,42 @@ static void intel_enable_crtc(struct intel_atomic_state *state,
>>   	intel_crtc_enable_pipe_crc(crtc);
>>   }
>>   
>> +static void skl_toggle_async_sync(struct intel_atomic_state *state,
> 
> skl_disable_async_flip_wa() maybe?
> 

Thanks for the review.
I'll change the name.
>> +				  struct intel_crtc *crtc,
>> +				  struct intel_crtc_state *new_crtc_state)
>> +{
>> +	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
>> +	struct intel_plane *plane;
>> +	struct intel_plane_state *new_plane_state;
>> +	u32 update_mask = new_crtc_state->update_planes;
>> +	u32 plane_ctl, surf_addr;
>> +	enum plane_id plane_id;
>> +	unsigned long irqflags;
>> +	enum pipe pipe;
> 
> Most of these things are only needed within the loop, so that's where
> the declarations should be.
> 

Sure, I'll move it inside the loop.
>> +	int i;
>> +
>> +	for_each_new_intel_plane_in_state(state, plane, new_plane_state, i) {
>> +		if (crtc->pipe != plane->pipe ||
>> +		    !(update_mask & BIT(plane->id)))
>> +			continue;
>> +
>> +		plane_id = plane->id;
>> +		pipe = plane->pipe;
>> +
> 
> I'd take the lock here so the rmw is fully protected.
> 

Sure, I'll move it here.
>> +		plane_ctl = intel_de_read_fw(dev_priv, PLANE_CTL(pipe, plane_id));
>> +		surf_addr = intel_de_read_fw(dev_priv, PLANE_SURF(pipe, plane_id));
>> +
>> +		plane_ctl &= ~PLANE_CTL_ASYNC_FLIP;
>> +
>> +		spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
>> +		intel_de_write_fw(dev_priv, PLANE_CTL(pipe, plane_id), plane_ctl);
>> +		intel_de_write_fw(dev_priv, PLANE_SURF(pipe, plane_id), surf_addr);
>> +		spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
>> +	}
>> +
>> +	intel_wait_for_vblank(dev_priv, crtc->pipe);
>> +}
>> +
>>   static void intel_update_crtc(struct intel_atomic_state *state,
>>   			      struct intel_crtc *crtc)
>>   {
>> @@ -15387,6 +15423,14 @@ static void intel_update_crtc(struct intel_atomic_state *state,
>>   	else
>>   		intel_fbc_enable(state, crtc);
>>   
>> +	/* WA for older platforms where async address update enable bit
> 
> s/older//
> 

Noted.
>> +	 * is double buffered.
> 
> "is double buffered and only latched at start of vblank" or
> something. Otherwise one is left wondering what the fuss is about.
> 

Sure, I'll update this.
>> +	 */
> 
> Multiline comment format should be
> /*
>   * blah
>   * blah
>   */
> 

I'll fix this.
>> +	if (old_crtc_state->uapi.async_flip &&
>> +	    !new_crtc_state->uapi.async_flip &&
>> +	    INTEL_GEN(dev_priv) <= 10 && INTEL_GEN(dev_priv) >= 9)
> 
> IS_GEN_RANGE(9, 10) or whatever it's called.
> 

Sure, I'll update this.
> I guess we might want to put this call into intel_pre_plane_update()
> since that's where all kinds of similar wait_for_vblank w/as live.
> 

Sure, I'll move this to intel_pre_plane_update()

Thanks,
Karthik.B.S
>> +		skl_toggle_async_sync(state, crtc, new_crtc_state);
>> +
>>   	/* Perform vblank evasion around commit operation */
>>   	intel_pipe_update_start(new_crtc_state);
>>   
>> -- 
>> 2.22.0
> 
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