On 08/02/17 13:25, Laurent Pinchart wrote:
> Hi Jyri,
>
> Thank you for the patch.
>
> On Tuesday 07 Feb 2017 16:41:20 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 <jsarha@xxxxxx>
>> ---
>> 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);
>> + return -EINVAL;
>
> This needs to be validated during the atomic check phase to avoid failures at
> commit time that are much harder to handle properly.
I agree, but that requires rewriting half of the dispc driver... This
and the few earlier ones from Jyri are quick fixes to major issues we've
found.
Tomi
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