[Intel-gfx] [PATCH 0/6] eDP DRRS based on frontbuffer tracking

[Ramalingam C]

On Tuesday 24 February 2015 06:21 AM, Daniel Vetter wrote:
> On Fri, Feb 13, 2015 at 03:32:58PM +0530, Ramalingam C wrote:
>> This series includes a preparation patch for drrs support across differnt
>> platforms in intel_dp_set_m_n along with last 5 pending patches of V3 eDP
>> DRRS patch series.
>>
>> New series is submitted to make the review more comfortable and
>> to display the dependancy of the patches explicitly.
>>
>> Durgadoss R (1):
>>    drm/i915: Enable eDP DRRS for CHV
>>
>> Ramalingam C (1):
>>    drm/i915: Add support for DRRS in intel_dp_set_m_n
>>
>> Vandana Kannan (4):
>>    drm/i915/bdw: Add support for DRRS to switch RR
>>    drm/i915: Support for RR switching on VLV
>>    Documentation/drm: DocBook integration for DRRS
>>    drm/i915: Add debugfs entry for DRRS
> Ok I've reviewed the locking for DRRS quickly now that it's all merged and
> it's deadlock-y:
>
> intel_edp_drrs_downclock_work grabs the drrs mutex. But in the disable
> function we cancel that work and wait for that to complete (cancel_sync)
> while holding the lock.
>
> Which means if the async work is running this will deadlock. The work
> cancel must be moved out of the critical section, and the work must
> double-check (after taking the lock) that drrs hasn't been disabled
> meanwhile (by checking drrs.dp, which we already do). intel_psr.c contains
> all that logic as an example.
>
> While you do that follow-up patch could we extract the drrs code into a
> new intel_drrs.c file? That would also simplify the kerneldoc includes a
> bit.
>
> Cheers, Daniel
Missed the possible deadlock window. I will upload a patch moving the 
cancellation of the deferred work out of the mutex protection asap.

As a heads up, in VPG we have implemented MIPI DRRS and also content 
based DRRS.

MIPI DRRS:
We have extended the DRRS to DSI encoder also on android codelines for 
BYT and CHV.


Content based DRRS:
We have implemented the interfaces
         to expose the DRRS capability and and the vrefresh supported
         to receive the request for the new vrefresh.

So based on required FPS for the display content to be rendered 
userspace, will place a request for the new vrefresh.

We have verified the functionality of this implementation on android 
devices for almost an year now.
I will rework on the implementation to adapt to the DRM-intel and submit 
a RFC to explain the complete design.

This RFC will have the generalized DRRS state machine for all encoders 
like eDP and DSI along with encoder support for DSI and eDP.
So as a result we will have the generic code for drrs state machine in 
intel_drrs.c totally separated from the encoder related code. Can we 
wait till then?


--Ram
>>   Documentation/DocBook/drm.tmpl       |   11 ++++
>>   drivers/gpu/drm/i915/i915_debugfs.c  |   99 ++++++++++++++++++++++++++++
>>   drivers/gpu/drm/i915/i915_reg.h      |    1 +
>>   drivers/gpu/drm/i915/intel_display.c |   32 ++++++---
>>   drivers/gpu/drm/i915/intel_dp.c      |  121 ++++++++++++++++++++++++++++++++--
>>   drivers/gpu/drm/i915/intel_drv.h     |   22 ++++++-
>>   6 files changed, 273 insertions(+), 13 deletions(-)
>>
>> -- 
>> 1.7.9.5
>>