drm/i915/wm: Modify latency programmed into PKG_C_LATENCY

Increase the latency programmed into PKG_C_LATENCY latency to be
a multiple of line time which is written into WM_LINETIME.

--v2
-Fix commit subject line [Sai Teja]
-Use individual DISPLAY_VER checks instead of range [Sai Teja]
-Initialize max_linetime [Sai Teja]

--v3
-take into account the scenario when adjusted_latency is 0 [Vinod]

--v4
-rename adjusted_latency to latency [Mitul]
-fix the condition in which dpkgc is disabled [Vinod]

--v5
-Add check to see if max_linetime is 0 [Vinod]

--v6
-Avoid nested if statements [Mitul]

WA: 22020299601
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241203084706.2126189-5-suraj.kandpal@intel.com

Author: surajk8

drivers/gpu/drm/i915/display/skl_watermark.c

@@ -2861,7 +2861,8 @@ intel_program_dpkgc_latency(struct intel_atomic_state *state)
 	struct drm_i915_private *i915 = to_i915(display->drm);
 	struct intel_crtc *crtc;
 	struct intel_crtc_state *new_crtc_state;
-	u32 max_latency = LNL_PKG_C_LATENCY_MASK;
+	u32 latency = LNL_PKG_C_LATENCY_MASK;
+	u32 max_linetime = 0;
 	u32 clear, val;
 	u32 added_wake_time = 0;
 	bool fixed_refresh_rate = false;
@@ -2875,18 +2876,26 @@ intel_program_dpkgc_latency(struct intel_atomic_state *state)
 		    (new_crtc_state->vrr.vmin == new_crtc_state->vrr.vmax &&
 		     new_crtc_state->vrr.vmin == new_crtc_state->vrr.flipline))
 			fixed_refresh_rate = true;
+
+		max_linetime = max(new_crtc_state->linetime, max_linetime);
 	}
 
 	if (fixed_refresh_rate) {
-		max_latency = skl_watermark_max_latency(i915, 1);
-		if (max_latency == 0)
-			max_latency = LNL_PKG_C_LATENCY_MASK;
+		latency = skl_watermark_max_latency(i915, 1);
+		/* Wa_22020299601 */
+		if ((latency && max_linetime) &&
+		    (DISPLAY_VER(display) == 20 || DISPLAY_VER(display) == 30)) {
+			latency = max_linetime * DIV_ROUND_UP(latency, max_linetime);
+		} else if (!latency) {
+			latency = LNL_PKG_C_LATENCY_MASK;
+		}
+
 		added_wake_time = DSB_EXE_TIME +
 			display->sagv.block_time_us;
 	}
 
 	clear = LNL_ADDED_WAKE_TIME_MASK | LNL_PKG_C_LATENCY_MASK;
-	val = REG_FIELD_PREP(LNL_PKG_C_LATENCY_MASK, max_latency) |
+	val = REG_FIELD_PREP(LNL_PKG_C_LATENCY_MASK, latency) |
 		REG_FIELD_PREP(LNL_ADDED_WAKE_TIME_MASK, added_wake_time);
 
 	intel_de_rmw(display, LNL_PKG_C_LATENCY, clear, val);