Commit ab6b2582 authored Mar 17, 2015 by Tomi Valkeinen

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 <tomi.valkeinen@ti.com>

parent f5a73482

drivers/video/fbdev/omap2/dss/dispc.c

+15 −0

Original line number	Diff line number	Diff line
		@@ -2326,6 +2326,21 @@ static int dispc_ovl_calc_scaling_34xx(unsigned long pclk, unsigned long lclk,
		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;