Re: [PATCH 1/2] mmc: renesas_sdhi: fix swiotlb buffer is full

Geert Uytterhoeven
2017-10-17T08:02:50Z

Hi Shimoda-san,

CC iommu

On Tue, Oct 17, 2017 at 9:30 AM, Yoshihiro Shimoda
<yoshihiro.shimoda.uh-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org> wrote:
> Since the commit de3ee99b097d ("mmc: Delete bounce buffer handling")
> deletes the bounce buffer handling, a request data size will be referred
> to max_{req,seg}_size instead of MMC_QUEUE_BOUNCESZ (64k bytes).
>
> In other hand, renesas_sdhi_internal_dmac.c will set very big value of
> max_{req,seg}_size because the max_blk_count is set to 0xffffffff.
> And then, "swiotlb buffer is full" happens because swiotlb can handle
> a memory size up to 256k bytes only (IO_TLB_SEGSIZE = 128 and
> IO_TLB_SHIFT = 11).
>
> So, this patch fixes the issue to set max_blk_count to 512. Then,
> the max_{req,seg}_size will be set to 256k bytes.
>
> Reported-by: Dirk Behme <dirk.behme-V5te9oGctAVWk0Htik3J/w@public.gmane.org>
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org>

Thanks for your patch!

> ---
> drivers/mmc/host/renesas_sdhi_internal_dmac.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/renesas_sdhi_internal_dmac.c b/drivers/mmc/host/renesas_sdhi_internal_dmac.c
> index f905f23..6c9b4b2 100644
> --- a/drivers/mmc/host/renesas_sdhi_internal_dmac.c
> +++ b/drivers/mmc/host/renesas_sdhi_internal_dmac.c
> @@ -80,8 +80,9 @@
> .scc_offset = 0x1000,
> .taps = rcar_gen3_scc_taps,
> .taps_num = ARRAY_SIZE(rcar_gen3_scc_taps),
> - /* Gen3 SDHI DMAC can handle 0xffffffff blk count, but seg = 1 */
> - .max_blk_count = 0xffffffff,
> + /* The swiotlb can handle memory size up to 256 kbytes for now. */
> + .max_blk_count = 512,

Fixing this in the individual drivers feels like the wrong solution to me.

iommu: Is there a better (generic) way to handle this?

> + /* Gen3 SDHI DMAC cannot handle scatter-gather. So, max_segs = 1 */
> .max_segs = 1,
> };

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org

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