Re: [PATCH v2 3/7] drm/i915: Compute dsi_clk from pixel clock

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

On Fri, 15 Nov 2013, Jani Nikula <jani.nikula@intel.com> wrote:
> On Sat, 09 Nov 2013, Shobhit Kumar <shobhit.kumar@intel.com> wrote:
>> Pixel clock based calculation is recommended in the MIPI host controller
>> documentation
>>
>> v2: Based on review comments from Jani and Ville
>>     - Use dsi_clk in KHz rather than converting in Hz and back to MHz
>>     - RR formula is retained though not used but return dsi_clk in KHz now
>>     - Moved the m-n-p changes into a separate patch
>>     - Removed the parameter check for intel_dsi->dsi_clock_freq. This will be
>>       bought back in if needed when appropriate panel drivers are done
>>
>> Signed-off-by: Vijayakumar Balakrishnan <vijayakumar.balakrishnan@intel.com>
>> Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_dsi_pll.c |   46 +++++++++++++++++++++++++++++-----
>>  1 file changed, 40 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dsi_pll.c b/drivers/gpu/drm/i915/intel_dsi_pll.c
>> index 44279b2..9f3e6b0 100644
>> --- a/drivers/gpu/drm/i915/intel_dsi_pll.c
>> +++ b/drivers/gpu/drm/i915/intel_dsi_pll.c
>> @@ -50,6 +50,8 @@ static const u32 lfsr_converts[] = {
>>  	71, 35							/* 91 - 92 */
>>  };
>>  
>> +#ifdef DSI_CLK_FROM_RR
>> +
>>  static u32 dsi_rr_formula(const struct drm_display_mode *mode,
>>  			  int pixel_format, int video_mode_format,
>>  			  int lane_count, bool eotp)
>> @@ -121,7 +123,7 @@ static u32 dsi_rr_formula(const struct drm_display_mode *mode,
>>  
>>  	/* the dsi clock is divided by 2 in the hardware to get dsi ddr clock */
>>  	dsi_bit_clock_hz = bytes_per_x_frames_x_lanes * 8;
>> -	dsi_clk = dsi_bit_clock_hz / (1000 * 1000);
>> +	dsi_clk = dsi_bit_clock_hz / 1000;
>>  
>>  	if (eotp && video_mode_format == VIDEO_MODE_BURST)
>>  		dsi_clk *= 2;
>> @@ -129,6 +131,38 @@ static u32 dsi_rr_formula(const struct drm_display_mode *mode,
>>  	return dsi_clk;
>>  }
>>  
>> +#else
>> +
>> +/* Get DSI clock from pixel clock */
>> +static u32 dsi_clk_from_pclk(const struct drm_display_mode *mode,
>> +			  int pixel_format, int lane_count)
>> +{
>> +	u32 dsi_clk_khz;
>> +	u32 bpp;
>> +
>> +	switch (pixel_format) {
>> +	default:
>> +	case VID_MODE_FORMAT_RGB888:
>> +	case VID_MODE_FORMAT_RGB666_LOOSE:
>> +		bpp = 24;
>> +		break;
>> +	case VID_MODE_FORMAT_RGB666:
>> +		bpp = 18;
>> +		break;
>> +	case VID_MODE_FORMAT_RGB565:
>> +		bpp = 16;
>> +		break;
>> +	}
>> +
>> +	/* DSI data rate = pixel clock * bits per pixel / lane count
>> +	   pixel clock is converted from KHz to Hz */
>> +	dsi_clk_khz = DIV_ROUND_CLOSEST(mode->clock * bpp, lane_count);
>> +
>> +	return dsi_clk_khz;
>> +}
>> +
>> +#endif
>> +
>>  #ifdef MNP_FROM_TABLE
>>  
>>  struct dsi_clock_table {
>> @@ -200,13 +234,14 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
>>  	u32 calc_p;
>>  	u32 m_seed;
>>  
>> -	if (dsi_clk < 300 || dsi_clk > 1150) {
>> +	/* dsi_clk is expected in KHZ */
>> +	if (dsi_clk < 300000 || dsi_clk > 1150000) {
>>  		DRM_ERROR("DSI CLK Out of Range\n");
>>  		return -ECHRNG;
>>  	}
>>  
>>  	ref_clk = 25000;
>> -	target_dsi_clk = dsi_clk * 1000;
>> +	target_dsi_clk = dsi_clk;
>
> The *other* dsi_calc_mnp() (with MNP_FROM_TABLE defined) remains
> unchanged, and bitrots. Either /= 1000 the input there, or better, if
> you don't see that the other function will be needed, just remove it.

Other than that,
Reviewed-by: Jani Nikula <jani.nikula@intel.com>




>
> BR,
> Jani.
>
>
>>  	error = 0xFFFFFFFF;
>>  	calc_m = 0;
>>  	calc_p = 0;
>> @@ -251,9 +286,8 @@ static void vlv_configure_dsi_pll(struct intel_encoder *encoder)
>>  	struct dsi_mnp dsi_mnp;
>>  	u32 dsi_clk;
>>  
>> -	dsi_clk = dsi_rr_formula(mode, intel_dsi->pixel_format,
>> -				 intel_dsi->video_mode_format,
>> -				 intel_dsi->lane_count, !intel_dsi->eot_disable);
>> +	dsi_clk = dsi_clk_from_pclk(mode, intel_dsi->pixel_format,
>> +						intel_dsi->lane_count);
>>  
>>  	ret = dsi_calc_mnp(dsi_clk, &dsi_mnp);
>>  	if (ret) {
>> -- 
>> 1.7.9.5
>>
>> _______________________________________________
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>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> -- 
> Jani Nikula, Intel Open Source Technology Center
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center