drm/i915: Compute dsi_clk from pixel clock

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

v3: Removed the unused mnp calculation from static table

Signed-off-by: Vijayakumar Balakrishnan <vijayakumar.balakrishnan@intel.com>
Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

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;
@@ -129,64 +131,37 @@ static u32 dsi_rr_formula(const struct drm_display_mode *mode,
 	return dsi_clk;
 }
 
-#ifdef MNP_FROM_TABLE
-
-struct dsi_clock_table {
-	u32 freq;
-	u8 m;
-	u8 p;
-};
-
-static const struct dsi_clock_table dsi_clk_tbl[] = {
-	{300, 72, 6}, {313, 75, 6}, {323, 78, 6}, {333, 80, 6},
-	{343, 82, 6}, {353, 85, 6}, {363, 87, 6}, {373, 90, 6},
-	{383, 92, 6}, {390, 78, 5}, {393, 79, 5}, {400, 80, 5},
-	{401, 80, 5}, {402, 80, 5}, {403, 81, 5}, {404, 81, 5},
-	{405, 81, 5}, {406, 81, 5}, {407, 81, 5}, {408, 82, 5},
-	{409, 82, 5}, {410, 82, 5}, {411, 82, 5}, {412, 82, 5},
-	{413, 83, 5}, {414, 83, 5}, {415, 83, 5}, {416, 83, 5},
-	{417, 83, 5}, {418, 84, 5}, {419, 84, 5}, {420, 84, 5},
-	{430, 86, 5}, {440, 88, 5}, {450, 90, 5}, {460, 92, 5},
-	{470, 75, 4}, {480, 77, 4}, {490, 78, 4}, {500, 80, 4},
-	{510, 82, 4}, {520, 83, 4}, {530, 85, 4}, {540, 86, 4},
-	{550, 88, 4}, {560, 90, 4}, {570, 91, 4}, {580, 70, 3},
-	{590, 71, 3}, {600, 72, 3}, {610, 73, 3}, {620, 74, 3},
-	{630, 76, 3}, {640, 77, 3}, {650, 78, 3}, {660, 79, 3},
-	{670, 80, 3}, {680, 82, 3}, {690, 83, 3}, {700, 84, 3},
-	{710, 85, 3}, {720, 86, 3}, {730, 88, 3}, {740, 89, 3},
-	{750, 90, 3}, {760, 91, 3}, {770, 92, 3}, {780, 62, 2},
-	{790, 63, 2}, {800, 64, 2}, {880, 70, 2}, {900, 72, 2},
-	{1000, 80, 2},		/* dsi clock frequency in Mhz*/
-};
+#else
 
-static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
+/* Get DSI clock from pixel clock */
+static u32 dsi_clk_from_pclk(const struct drm_display_mode *mode,
+			  int pixel_format, int lane_count)
 {
-	unsigned int i;
-	u8 m;
-	u8 n;
-	u8 p;
-	u32 m_seed;
-
-	if (dsi_clk < 300 || dsi_clk > 1000)
-		return -ECHRNG;
+	u32 dsi_clk_khz;
+	u32 bpp;
 
-	for (i = 0; i <= ARRAY_SIZE(dsi_clk_tbl); i++) {
-		if (dsi_clk_tbl[i].freq > dsi_clk)
-			break;
+	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;
 	}
 
-	m = dsi_clk_tbl[i].m;
-	p = dsi_clk_tbl[i].p;
-	m_seed = lfsr_converts[m - 62];
-	n = 1;
-	dsi_mnp->dsi_pll_ctrl = 1 << (DSI_PLL_P1_POST_DIV_SHIFT + p - 2);
-	dsi_mnp->dsi_pll_div = (n - 1) << DSI_PLL_N1_DIV_SHIFT |
-		m_seed << DSI_PLL_M1_DIV_SHIFT;
+	/* 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 0;
+	return dsi_clk_khz;
 }
 
-#else
+#endif
 
 static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
 {
@@ -200,13 +175,14 @@ 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;
@@ -235,8 +211,6 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
 	return 0;
 }
 
-#endif
-
 /*
  * XXX: The muxing and gating is hard coded for now. Need to add support for
  * sharing PLLs with two DSI outputs.
@@ -251,9 +225,8 @@ 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) {