drm/i915/glk: Program dphy param reg for GLK

For GEMINILAKE, dphy param reg values are programmed in terms
of HS byte clock count while for older platforms in terms of
HS ddr clk count.

v2: Added comments to clarify ddr clock count calculation
v3: Use multiplier variable instead of IS_GEMINILAKE()
check everywhere (Jani)
Signed-off-by: Deepak M <m.deepak@intel.com>
Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1487335415-14766-2-git-send-email-madhav.chauhan@intel.com

drivers/gpu/drm/i915/intel_dsi_panel_vbt.c

@@ -571,6 +571,7 @@ struct drm_panel *vbt_panel_init(struct intel_dsi *intel_dsi, u16 panel_id)
 	u32 tclk_prepare_clkzero, ths_prepare_hszero;
 	u32 lp_to_hs_switch, hs_to_lp_switch;
 	u32 pclk, computed_ddr;
+	u32 mul;
 	u16 burst_mode_ratio;
 	enum port port;
 
@@ -674,11 +675,6 @@ struct drm_panel *vbt_panel_init(struct intel_dsi *intel_dsi, u16 panel_id)
 		break;
 	}
 
-	/*
-	 * ui(s) = 1/f [f in hz]
-	 * ui(ns) = 10^9 / (f*10^6) [f in Mhz] -> 10^3/f(Mhz)
-	 */
-
 	/* in Kbps */
 	ui_num = NS_KHZ_RATIO;
 	ui_den = bitrate;
@@ -692,21 +688,26 @@ struct drm_panel *vbt_panel_init(struct intel_dsi *intel_dsi, u16 panel_id)
 	 */
 	intel_dsi->lp_byte_clk = DIV_ROUND_UP(tlpx_ns * ui_den, 8 * ui_num);
 
-	/* count values in UI = (ns value) * (bitrate / (2 * 10^6))
+	/* DDR clock period = 2 * UI
+	 * UI(sec) = 1/(bitrate * 10^3) (bitrate is in KHZ)
+	 * UI(nsec) = 10^6 / bitrate
+	 * DDR clock period (nsec) = 2 * UI = (2 * 10^6)/ bitrate
+	 * DDR clock count  = ns_value / DDR clock period
 	 *
-	 * Since txddrclkhs_i is 2xUI, all the count values programmed in
-	 * DPHY param register are divided by 2
-	 *
-	 * prepare count
+	 * For GEMINILAKE dphy_param_reg will be programmed in terms of
+	 * HS byte clock count for other platform in HS ddr clock count
 	 */
+	mul = IS_GEMINILAKE(dev_priv) ? 8 : 2;
 	ths_prepare_ns = max(mipi_config->ths_prepare,
 			     mipi_config->tclk_prepare);
-	prepare_cnt = DIV_ROUND_UP(ths_prepare_ns * ui_den, ui_num * 2);
+
+	/* prepare count */
+	prepare_cnt = DIV_ROUND_UP(ths_prepare_ns * ui_den, ui_num * mul);
 
 	/* exit zero count */
 	exit_zero_cnt = DIV_ROUND_UP(
 				(ths_prepare_hszero - ths_prepare_ns) * ui_den,
-				ui_num * 2
+				ui_num * mul
 				);
 
 	/*
@@ -721,11 +722,11 @@ struct drm_panel *vbt_panel_init(struct intel_dsi *intel_dsi, u16 panel_id)
 	/* clk zero count */
 	clk_zero_cnt = DIV_ROUND_UP(
 				(tclk_prepare_clkzero -	ths_prepare_ns)
-			* ui_den, 2 * ui_num);
+				* ui_den, ui_num * mul);
 
 	/* trail count */
 	tclk_trail_ns = max(mipi_config->tclk_trail, mipi_config->ths_trail);
-	trail_cnt = DIV_ROUND_UP(tclk_trail_ns * ui_den, 2 * ui_num);
+	trail_cnt = DIV_ROUND_UP(tclk_trail_ns * ui_den, ui_num * mul);
 
 	if (prepare_cnt > PREPARE_CNT_MAX ||
 		exit_zero_cnt > EXIT_ZERO_CNT_MAX ||