On 07/02/17 16:41, Jyri Sarha wrote:
> 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, 1 byte per pixel color format appear 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 <jsa...@ti.com>
> ---
> 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..61daef6 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_to_bpp(color_mode) > 8) {
> + /*
> + 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, 1 byte per pixel color format appear 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 (x-decimation factor %d > 4)",
> + *decim_x);I think the error message could be improved. A normal user could hit this when setting up a plane, and I'm quite sure the above doesn't give any clue to the user what the issue is (too much downscaling). Tomi
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