Re: [PATCH 5/5] drm/i915/bdw: Add support for DRRS to switch RR

[Vandana Kannan <vandana.kannan@intel.com>]

On Dec-17-2013 6:00 PM, Chris Wilson wrote:
> On Tue, Dec 17, 2013 at 10:58:27AM +0530, Vandana Kannan wrote:
>> For Broadwell, there is one instance of Transcoder MN values per transcoder.
>> For dynamic switching between multiple refreshr rates, M/N values may be
>> reprogrammed on the fly. Link N programming triggers update of all data and
>> link M & N registers and the new M/N values will be used in the next frame
>> that is output.
>>
>> Signed-off-by: Vandana Kannan <vandana.kannan@intel.com>
>> Signed-off-by: Pradeep Bhat <pradeep.bhat@intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_dp.c |   23 +++++++++++++++++++----
>>  1 file changed, 19 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 209be3c..183cfd7 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -798,9 +798,15 @@ intel_dp_set_m2_n2(struct intel_crtc *crtc, struct intel_link_m_n *m_n)
>>  	struct drm_i915_private *dev_priv = dev->dev_private;
>>  	enum transcoder transcoder = crtc->config.cpu_transcoder;
>>  
>> -	if (INTEL_INFO(dev)->gen >= 5 && INTEL_INFO(dev)->gen < 8) {
>> +	if (INTEL_INFO(dev)->gen >= 8) {
>> +		I915_WRITE(PIPE_DATA_M1(transcoder),
>> +			TU_SIZE(m_n->tu) | m_n->gmch_m);
>> +		I915_WRITE(PIPE_DATA_N1(transcoder), m_n->gmch_n);
>> +		I915_WRITE(PIPE_LINK_M1(transcoder), m_n->link_m);
>> +		I915_WRITE(PIPE_LINK_N1(transcoder), m_n->link_n);
>> +	} else if (INTEL_INFO(dev)->gen >= 5 && INTEL_INFO(dev)->gen < 8) {
> 
> Ouch. Double ouch later.
> -Chris
> 
We are looking to write in M1/N1 registers for BDW and M2/N2 registers
for HSW and below. What is your suggestion on how to implement this ?