Re: [Intel-gfx] [PATCH] drm/i915/mst: use intel_de_rmw() to simplify VC payload alloc set/clear

[Jani Nikula <jani.nikula@intel.com>]

On Fri, 13 Aug 2021, Jani Nikula <jani.nikula@intel.com> wrote:
> On Fri, 13 Aug 2021, Rodrigo Vivi <rodrigo.vivi@intel.com> wrote:
>> On Fri, Aug 13, 2021 at 02:56:10PM +0300, Jani Nikula wrote:
>>> Less is more, fewer lines to wonder about.
>>> 
>>> Cc: Manasi Navare <manasi.d.navare@intel.com>
>>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>>
>> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
>
> Thanks!

And pushed.

BR,
Jani.

>
>> although sometimes I get myself wondering we might get in some
>> case where our check inside the rmw function, to avoid writing the
>> same value, could cause some situation where we should perform
>> the write operation regardless.
>
> Me too. I could be persuaded to change the rmw function to not optimize
> the write away.
>
> BR,
> Jani.
>
>>
>>> ---
>>>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 9 ++-------
>>>  1 file changed, 2 insertions(+), 7 deletions(-)
>>> 
>>> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
>>> index 8d13d7b26a25..9859c0334ebc 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
>>> @@ -396,7 +396,6 @@ static void intel_mst_post_disable_dp(struct intel_atomic_state *state,
>>>  		to_intel_connector(old_conn_state->connector);
>>>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>>>  	bool last_mst_stream;
>>> -	u32 val;
>>>  
>>>  	intel_dp->active_mst_links--;
>>>  	last_mst_stream = intel_dp->active_mst_links == 0;
>>> @@ -412,12 +411,8 @@ static void intel_mst_post_disable_dp(struct intel_atomic_state *state,
>>>  
>>>  	clear_act_sent(encoder, old_crtc_state);
>>>  
>>> -	val = intel_de_read(dev_priv,
>>> -			    TRANS_DDI_FUNC_CTL(old_crtc_state->cpu_transcoder));
>>> -	val &= ~TRANS_DDI_DP_VC_PAYLOAD_ALLOC;
>>> -	intel_de_write(dev_priv,
>>> -		       TRANS_DDI_FUNC_CTL(old_crtc_state->cpu_transcoder),
>>> -		       val);
>>> +	intel_de_rmw(dev_priv, TRANS_DDI_FUNC_CTL(old_crtc_state->cpu_transcoder),
>>> +		     TRANS_DDI_DP_VC_PAYLOAD_ALLOC, 0);
>>>  
>>>  	wait_for_act_sent(encoder, old_crtc_state);
>>>  
>>> -- 
>>> 2.20.1
>>> 

-- 
Jani Nikula, Intel Open Source Graphics Center