Re: [PATCH] drm/i915: Skip DDI PLL selection for DSI

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

On Tue, 09 Feb 2016, "Thulasimani, Sivakumar" <sivakumar.thulasimani@intel.com> wrote:
> On 2/5/2016 4:59 PM, Mika Kahola wrote:
>> Skip DDI PLL selection if display type is DSI/MIPI.
>>
>> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_display.c | 9 +++++++--
>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>> index d7de2a5..5da98b2 100644
>> --- a/drivers/gpu/drm/i915/intel_display.c
>> +++ b/drivers/gpu/drm/i915/intel_display.c
>> @@ -9902,8 +9902,13 @@ static void broadwell_modeset_commit_cdclk(struct drm_atomic_state *old_state)
>>   static int haswell_crtc_compute_clock(struct intel_crtc *crtc,
>>   				      struct intel_crtc_state *crtc_state)
>>   {
>> -	if (!intel_ddi_pll_select(crtc, crtc_state))
>> -		return -EINVAL;
>> +	struct intel_encoder *intel_encoder =
>> +		intel_ddi_get_crtc_new_encoder(crtc_state);
>> +
>> +	if (intel_encoder->type != INTEL_OUTPUT_DSI) {
>> +		if (!intel_ddi_pll_select(crtc, crtc_state))
>> +			return -EINVAL;
>> +	}
>>   
> can this be moved inside bxt_ddi_pll_select ? we can avoid this check for
> other platforms that also execute this function.

I asked Mika to do it this way, but if you feel strongly about it I
guess I could be persuaded otherwise too.

My main point is, if we pass on DSI encoders to DDI functions in some
cases but mostly not, it will muddy the waters and eventually people end
up checking for "is dsi" all around DDI just because they can't be
bothered to check if the functions are really called for DDI only or
not. It's more of a maintainability concern than anything else.

BR,
Jani.



>
> regards,
> Sivakumar
>>   	crtc->lowfreq_avail = false;
>>   
>

-- 
Jani Nikula, Intel Open Source Technology Center
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