From 1b30ab0c40a99da347c1ab83c30b485e03fe9f64 Mon Sep 17 00:00:00 2001 From: Jyri Sarha Date: Wed, 8 Feb 2017 16:08:06 +0200 Subject: [PATCH] drm/omapdrm: dispc: Refuse x-decimation above 4 for all but 8-bit formats Let's disable all scaling that requires horizontal decimation with higher factor than 4, until we have better estimates of what we can and can not do. However, NV12 color format appears to work Ok with all decimation factors. When decimating horizontally by more that 4 the dss is not able to fetch the data in burst mode. When this happens it is hard to tell if there enough bandwidth. Despite what theory says this appears to be true also for 16-bit color formats. Signed-off-by: Jyri Sarha Acked-by: Laurent Pinchart Signed-off-by: Tomi Valkeinen --- drivers/gpu/drm/omapdrm/dss/dispc.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/gpu/drm/omapdrm/dss/dispc.c b/drivers/gpu/drm/omapdrm/dss/dispc.c index 5554b72..d956e626 100644 --- a/drivers/gpu/drm/omapdrm/dss/dispc.c +++ b/drivers/gpu/drm/omapdrm/dss/dispc.c @@ -2506,6 +2506,25 @@ static int dispc_ovl_calc_scaling_44xx(unsigned long pclk, unsigned long lclk, return -EINVAL; } + if (*decim_x > 4 && color_mode != OMAP_DSS_COLOR_NV12) { + /* + * Let's disable all scaling that requires horizontal + * decimation with higher factor than 4, until we have + * better estimates of what we can and can not + * do. However, NV12 color format appears to work Ok + * with all decimation factors. + * + * When decimating horizontally by more that 4 the dss + * is not able to fetch the data in burst mode. When + * this happens it is hard to tell if there enough + * bandwidth. Despite what theory says this appears to + * be true also for 16-bit color formats. + */ + DSSERR("Not enough bandwidth, too much downscaling (x-decimation factor %d > 4)", *decim_x); + + return -EINVAL; + } + *core_clk = dispc.feat->calc_core_clk(pclk, in_width, in_height, out_width, out_height, mem_to_mem); return 0; -- 2.7.4