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

[Shobhit Kumar <shobhit.kumar@xxxxxxxxx>]

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@xxxxxxxxx>
Signed-off-by: Shobhit Kumar <shobhit.kumar@xxxxxxxxx>
---
 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;
 	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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