[PATCH v2] OMAPDSS: DISPC: Fix 34xx overlay scaling calculation

[Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>]

From: Ivaylo Dimitrov <freemangordon@abv.bg>

commit 7faa92339bbb1e6b9a80983b206642517327eb75 OMAPDSS: DISPC: Handle
synclost errors in OMAP3 introduces limits check to prevent SYNCLOST errors
on OMAP3. However, it misses the logic found in Nokia kernels that is
needed to correctly calculate whether 3 tap or 5 tap rescaler to be used as
well as the logic to fallback to 3 taps if 5 taps clock results in too
tight horizontal timings. Without that patch "horizontal timing too tight"
errors are seen when a video with resolution above 640x350 is tried to be
played. The patch is a forward-ported logic found in Nokia N900 and N9/50
kernels.

Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
---
 drivers/video/omap2/dss/dispc.c |   31 ++++++++++++++++++++++---------
 1 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/video/omap2/dss/dispc.c b/drivers/video/omap2/dss/dispc.c
index 67e413e..66e0849 100644
--- a/drivers/video/omap2/dss/dispc.c
+++ b/drivers/video/omap2/dss/dispc.c
@@ -1999,7 +1999,8 @@ static void calc_tiler_rotation_offset(u16 screen_width, u16 width,
  */
 static int check_horiz_timing_omap3(unsigned long pclk, unsigned long lclk,
 		const struct omap_video_timings *t, u16 pos_x,
-		u16 width, u16 height, u16 out_width, u16 out_height)
+		u16 width, u16 height, u16 out_width, u16 out_height,
+		bool five_taps)
 {
 	const int ds = DIV_ROUND_UP(height, out_height);
 	unsigned long nonactive;
@@ -2019,6 +2020,10 @@ static int check_horiz_timing_omap3(unsigned long pclk, unsigned long lclk,
 	if (blank <= limits[i])
 		return -EINVAL;
 
+	/* FIXME add checks for 3-tap filter once the limitations are known */
+	if (!five_taps)
+		return 0;
+
 	/*
 	 * Pixel data should be prepared before visible display point starts.
 	 * So, atleast DS-2 lines must have already been fetched by DISPC
@@ -2194,22 +2199,30 @@ static int dispc_ovl_calc_scaling_34xx(unsigned long pclk, unsigned long lclk,
 	do {
 		in_height = DIV_ROUND_UP(height, *decim_y);
 		in_width = DIV_ROUND_UP(width, *decim_x);
-		*core_clk = calc_core_clk_five_taps(pclk, mgr_timings,
-			in_width, in_height, out_width, out_height, color_mode);
-
-		error = check_horiz_timing_omap3(pclk, lclk, mgr_timings,
-				pos_x, in_width, in_height, out_width,
-				out_height);
+		*five_taps = in_height > out_height;
 
 		if (in_width > maxsinglelinewidth)
 			if (in_height > out_height &&
 						in_height < out_height * 2)
 				*five_taps = false;
-		if (!*five_taps)
+again:
+		if (*five_taps)
+			*core_clk = calc_core_clk_five_taps(pclk, mgr_timings,
+						in_width, in_height, out_width,
+						out_height, color_mode);
+		else
 			*core_clk = dispc.feat->calc_core_clk(pclk, in_width,
 					in_height, out_width, out_height,
 					mem_to_mem);
 
+		error = check_horiz_timing_omap3(pclk, lclk, mgr_timings,
+				pos_x, in_width, in_height, out_width,
+				out_height, *five_taps);
+		if (error && *five_taps) {
+			*five_taps = false;
+			goto again;
+		}
+
 		error = (error || in_width > maxsinglelinewidth * 2 ||
 			(in_width > maxsinglelinewidth && *five_taps) ||
 			!*core_clk || *core_clk > dispc_core_clk_rate());
@@ -2226,7 +2239,7 @@ static int dispc_ovl_calc_scaling_34xx(unsigned long pclk, unsigned long lclk,
 	} while (*decim_x <= *x_predecim && *decim_y <= *y_predecim && error);
 
 	if (check_horiz_timing_omap3(pclk, lclk, mgr_timings, pos_x, width,
-				height, out_width, out_height)){
+				height, out_width, out_height, *five_taps)) {
 			DSSERR("horizontal timing too tight\n");
 			return -EINVAL;
 	}
-- 
1.5.6.1