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OMAPDSS: DISPC: add check for scaling limits

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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 <tomi.valkeinen@ti.com>
This commit is contained in:
Tomi Valkeinen 2015-03-17 15:31:10 +02:00
parent f5a734827b
commit ab6b2582b8
1 changed files with 15 additions and 0 deletions
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15
drivers/video/fbdev/omap2/dss/dispc.c
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@ -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;