[Intel-gfx] [PATCH v3 05/11] drm/i915/gen9+: Do not initialise active_crtcs for !modeset

[Maarten Lankhorst]

Op 08-11-16 om 15:11 schreef Ville Syrjälä:
> On Tue, Nov 08, 2016 at 01:55:36PM +0100, Maarten Lankhorst wrote:
>> This is a hack and not needed. Use the right mask by checking
>> intel_state->modeset. This works for watermark sanitization too.
>>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_pm.c | 38 +++++++++++++++-----------------------
>>  1 file changed, 15 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index 02f52b52a03d..d38a46efcfed 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>> @@ -3089,26 +3089,22 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
>>  	struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
>>  	struct drm_i915_private *dev_priv = to_i915(dev);
>>  	struct drm_crtc *for_crtc = cstate->base.crtc;
>> -	unsigned int pipe_size, ddb_size;
>> +	unsigned int pipe_size, ddb_size, active_crtcs;
>>  	int nth_active_pipe;
>>  
>> +	if (intel_state->modeset)
>> +		active_crtcs = intel_state->active_crtcs;
>> +	else
>> +		active_crtcs = dev_priv->active_crtcs;
> What's the story with the locking here?
if !modeset, 3 things can happen:
1. fastset, connection_mutex held, dev_priv->active_crtcs cannot change.
2. crtc disabled, active_crtcs is potentially garbage, but harmless since we don't write disabled wm's when the crtc is already disabled.
(same as what happens currently)
3. crtc enabled, dev_priv->active_crtcs is valid because ddb reallocation requires locking all active crtc's for reallocation,
which requires taking this lock for this crtc.

This wouldn't be valid for gen8-, but is valid because of skl reallocation requirements.

~Maarten