The current driver does both x and y decimation on OMAP3 DSS. Testing
shows that x decimation rarely works, leading to underflows.
The exact reason for this is unclear, as the underflows seem to happen
even with low pixel clock rates, and I would presume that if the DSS can
manage a display with 140MHz pixel clock, it could manage x decimation
with factor 2 with a low pixel clock (~30MHz).
So it is possible that there is a problem somewhere else, in memory
management, or DSS DMA, or similar. I have not found anything that would
help this.
So, to fix the downscaling scaling, this patch removes x decimation for
OMAP3. This will limit some of the more demanding downscaling scenarios,
but one could argue that using DSS to downscale such a large amount is
insane in the first place, as the produced image is rather bad quality.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
---
drivers/video/fbdev/omap2/dss/dispc.c | 13 ++-----------
1 file changed, 2 insertions(+), 11 deletions(-)
diff --git a/drivers/video/fbdev/omap2/dss/dispc.c b/drivers/video/fbdev/omap2/dss/dispc.c
index 0bdb587cb48c..646d94a71a79 100644
--- a/drivers/video/fbdev/omap2/dss/dispc.c
+++ b/drivers/video/fbdev/omap2/dss/dispc.c
@@ -2300,7 +2300,6 @@ static int dispc_ovl_calc_scaling_34xx(unsigned long pclk, unsigned long lclk,
{
int error;
u16 in_width, in_height;
- int min_factor = min(*decim_x, *decim_y);
const int maxsinglelinewidth =
dss_feat_get_param_max(FEAT_PARAM_LINEWIDTH);
@@ -2349,16 +2348,8 @@ again:
}
}
- if (error) {
- if (*decim_x == *decim_y) {
- *decim_x = min_factor;
- ++*decim_y;
- } else {
- swap(*decim_x, *decim_y);
- if (*decim_x < *decim_y)
- ++*decim_x;
- }
- }
+ if (error)
+ ++*decim_y;
} while (*decim_x <= *x_predecim && *decim_y <= *y_predecim && error);
if (error) {
--
2.1.4
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