Re: [PATCH v3 08/16] gpu: host1x: Use correct semantics for HOST1X_CHANNEL_DMAEND

Dmitry Osipenko
2019-02-01T14:47:35Z

01.02.2019 16:28, Thierry Reding пишет:
> From: Thierry Reding <treding@nvidia.com>
>
> The HOST1X_CHANNEL_DMAEND is an offset relative to the value written to
> the HOST1X_CHANNEL_DMASTART register, but it is currently treated as an
> absolute address. This can cause SMMU faults if the CDMA fetches past a
> pushbuffer's IOMMU mapping.
>
> Properly setting the DMAEND prevents the CDMA from fetching beyond that
> address and avoid such issues. This is currently not observed because a
> whole (almost) page of essentially scratch space absorbs any excessive
> prefetching by CDMA. However, changing the number of slots in the push
> buffer can trigger these SMMU faults.
>
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---
> drivers/gpu/host1x/hw/cdma_hw.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/host1x/hw/cdma_hw.c b/drivers/gpu/host1x/hw/cdma_hw.c
> index 485aef5761af..a24c090ac96f 100644
> --- a/drivers/gpu/host1x/hw/cdma_hw.c
> +++ b/drivers/gpu/host1x/hw/cdma_hw.c
> @@ -75,7 +75,7 @@ static void cdma_start(struct host1x_cdma *cdma)
>
> cdma->last_pos = cdma->push_buffer.pos;
> start = cdma->push_buffer.dma;
> - end = start + cdma->push_buffer.size + 4;
> + end = cdma->push_buffer.size + 4;
>
> host1x_ch_writel(ch, HOST1X_CHANNEL_DMACTRL_DMASTOP,
> HOST1X_CHANNEL_DMACTRL);
> @@ -126,7 +126,7 @@ static void cdma_timeout_restart(struct host1x_cdma *cdma, u32 getptr)
> HOST1X_CHANNEL_DMACTRL);
>
> start = cdma->push_buffer.dma;
> - end = start + cdma->push_buffer.size + 4;
> + end = cdma->push_buffer.size + 4;
>
> /* set base, end pointer (all of memory) */
> host1x_ch_writel(ch, lower_32_bits(start), HOST1X_CHANNEL_DMASTART);
>

Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>