From ab6b2582b8f931f8f324fbf7bcb8338b8fc1eded Mon Sep 17 00:00:00 2001 From: Tomi Valkeinen Date: Tue, 17 Mar 2015 15:31:10 +0200 Subject: [PATCH] OMAPDSS: DISPC: add check for scaling limits On OMAP3/AM43xx some scaling factors cause underflows/synclosts. After studying this, I found that sometimes the driver uses three-tap scaling with downscaling factor smaller than x0.5. This causes issues, as x0.5 is the limit for three-tap scaling. The driver has FEAT_PARAM_DOWNSCALE parameter, but that seems to be for five-tap scaling, which allows scaling down to x0.25. This patch adds checks for both horizontal and vertical scaling. For horizontal the HW always uses 5 taps, so the limit is x0.25. Signed-off-by: Tomi Valkeinen --- drivers/video/fbdev/omap2/dss/dispc.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/drivers/video/fbdev/omap2/dss/dispc.c b/drivers/video/fbdev/omap2/dss/dispc.c index cc61513afdb4..ddce8fcfc5c1 100644 --- a/drivers/video/fbdev/omap2/dss/dispc.c +++ b/drivers/video/fbdev/omap2/dss/dispc.c @@ -2326,6 +2326,21 @@ again: error = (error || in_width > maxsinglelinewidth * 2 || (in_width > maxsinglelinewidth && *five_taps) || !*core_clk || *core_clk > dispc_core_clk_rate()); + + if (!error) { + /* verify that we're inside the limits of scaler */ + if (in_width / 4 > out_width) + error = 1; + + if (*five_taps) { + if (in_height / 4 > out_height) + error = 1; + } else { + if (in_height / 2 > out_height) + error = 1; + } + } + if (error) { if (*decim_x == *decim_y) { *decim_x = min_factor; -- 2.20.1