[PATCH 3/4] drm/i915: Compute dsi_clk from pixel clock

[Shobhit Kumar <shobhit.kumar@intel.com>]

Minor modification to m_n_p calculations as well

Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
---
 drivers/gpu/drm/i915/intel_dsi_pll.c |   75 ++++++++++++++++++++++++++++------
 1 file changed, 63 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dsi_pll.c b/drivers/gpu/drm/i915/intel_dsi_pll.c
index 44279b2..bf12335 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)
@@ -129,6 +131,40 @@ 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_bit_clock_hz, dsi_clk;
+	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_bit_clock_hz = (((mode->clock * 1000) * bpp) / lane_count);
+
+	/* DSI clock rate */
+	dsi_clk = dsi_bit_clock_hz / (1000 * 1000);
+	return dsi_clk;
+}
+
+#endif
+
 #ifdef MNP_FROM_TABLE
 
 struct dsi_clock_table {
@@ -208,29 +244,42 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
 	ref_clk = 25000;
 	target_dsi_clk = dsi_clk * 1000;
 	error = 0xFFFFFFFF;
+	tmp_error = 0xFFFFFFFF;
 	calc_m = 0;
 	calc_p = 0;
 
 	for (m = 62; m <= 92; m++) {
 		for (p = 2; p <= 6; p++) {
-
+			/* Find the optimal m and p divisors
+			with minimal error +/- the required clock */
 			calc_dsi_clk = (m * ref_clk) / p;
-			if (calc_dsi_clk >= target_dsi_clk) {
+			if (calc_dsi_clk == target_dsi_clk) {
+				calc_m = m;
+				calc_p = p;
+				error = 0;
+				break;
+			} else if (calc_dsi_clk > target_dsi_clk)
 				tmp_error = calc_dsi_clk - target_dsi_clk;
-				if (tmp_error < error) {
-					error = tmp_error;
-					calc_m = m;
-					calc_p = p;
-				}
+			else
+				tmp_error = target_dsi_clk - calc_dsi_clk;
+
+			if (tmp_error < error) {
+				error = tmp_error;
+				calc_m = m;
+				calc_p = p;
 			}
 		}
+
+		if (error == 0)
+			break;
 	}
 
 	m_seed = lfsr_converts[calc_m - 62];
 	n = 1;
+
 	dsi_mnp->dsi_pll_ctrl = 1 << (DSI_PLL_P1_POST_DIV_SHIFT + calc_p - 2);
 	dsi_mnp->dsi_pll_div = (n - 1) << DSI_PLL_N1_DIV_SHIFT |
-		m_seed << DSI_PLL_M1_DIV_SHIFT;
+					m_seed << DSI_PLL_M1_DIV_SHIFT;
 
 	return 0;
 }
@@ -249,11 +298,13 @@ static void vlv_configure_dsi_pll(struct intel_encoder *encoder)
 	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
 	int ret;
 	struct dsi_mnp dsi_mnp;
-	u32 dsi_clk;
+	u32 dsi_clk = 0;
 
-	dsi_clk = dsi_rr_formula(mode, intel_dsi->pixel_format,
-				 intel_dsi->video_mode_format,
-				 intel_dsi->lane_count, !intel_dsi->eot_disable);
+	if (intel_dsi->dsi_clock_freq)
+		dsi_clk = intel_dsi->dsi_clock_freq;
+	else
+		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