Hi Kieran,
On Wed, Mar 18, 2020 at 6:23 PM Kieran Bingham
<kieran.bingham+renesas@xxxxxxxxxxxxxxxx> wrote:
> Enabling CONFIG_DMA_API_DEBUG=y and CONFIG_DMA_API_DEBUG_SG=y will
> enable extra validation on DMA operations ensuring that the size
> restraints are met.
>
> When using the FCP in conjunction with the VSP1/DU, and display frames,
> the size of the DMA operations is larger than the default maximum
> segment size reported by the DMA core (64K). With the DMA debug enabled,
> this produces a warning such as the following:
>
> "DMA-API: rcar-fcp fea27000.fcp: mapping sg segment longer than device"
... claims to support [len=3145728] [max=65536]
> We have no specific limitation on the segment size which isn't already
> handled by the VSP1/DU which actually handles the DMA allcoations and
> buffer management, so define a maximum segment size of up to 4GB (a 32
> bit mask).
Reported-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Fixes: 7b49235e83b2 ("[media] v4l: Add Renesas R-Car FCP driver")
>
> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
The warning is gone, so:
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Haven't tested the actual display, though.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
