On 08/04/2018 01:00 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> The patch below does not apply to the 4.17-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
> thanks,
>
> greg k-h
Sorry my bad, by we don't need it after all. The patch this was fixing was merged
in 4.18 and not 4.17 so we can drop this.
Thx,
-Vineet
>
> ------------------ original commit in Linus's tree ------------------
>
> From 4c612add7b18844ddd733ebdcbe754520155999b Mon Sep 17 00:00:00 2001
> From: Eugeniy Paltsev <Eugeniy.Paltsev@xxxxxxxxxxxx>
> Date: Tue, 24 Jul 2018 17:13:02 +0300
> Subject: [PATCH] ARC: dma [non IOC]: fix arc_dma_sync_single_for_(device|cpu)
>
> ARC backend for dma_sync_single_for_(device|cpu) was broken as it was
> not honoring the @dir argument and simply forcing it based on the call:
> - arc_dma_sync_single_for_device(dir) assumed DMA_TO_DEVICE (cache wback)
> - arc_dma_sync_single_for_cpu(dir) assumed DMA_FROM_DEVICE (cache inv)
>
> This is not true given the DMA API programming model and has been
> discussed here [1] in some detail.
>
> Interestingly while the deficiency has been there forever, it only started
> showing up after 4.17 dma common ops rework, commit a8eb92d02dd7
> ("arc: fix arc_dma_{map,unmap}_page") which wired up these calls under the
> more commonly used dma_map_page API triggering the issue.
>
> [1]: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2018_5_18_979&d=DwIDAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=c14YS-cH-kdhTOW89KozFhBtBJgs1zXscZojEZQ0THs&m=7aV-FuW2twpiMTknC5mcDf1AngIn1HqXHwIhZoysGW4&s=EeRw-AeiwFbuvEid0L-9vik7eJbDwyNrwCjmcHVSSyo&e=
> Fixes: commit a8eb92d02dd7 ("arc: fix arc_dma_{map,unmap}_page")
> Cc: stable@xxxxxxxxxx # v4.17+
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@xxxxxxxxxxxx>
> Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
> [vgupta: reworked changelog]
>
> diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
> index 8c1071840979..ec47e6079f5d 100644
> --- a/arch/arc/mm/dma.c
> +++ b/arch/arc/mm/dma.c
> @@ -129,14 +129,59 @@ int arch_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> return ret;
> }
>
> +/*
> + * Cache operations depending on function and direction argument, inspired by
> + * https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2018_5_18_979&d=DwIDAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=c14YS-cH-kdhTOW89KozFhBtBJgs1zXscZojEZQ0THs&m=7aV-FuW2twpiMTknC5mcDf1AngIn1HqXHwIhZoysGW4&s=EeRw-AeiwFbuvEid0L-9vik7eJbDwyNrwCjmcHVSSyo&e=
> + * "dma_sync_*_for_cpu and direction=TO_DEVICE (was Re: [PATCH 02/20]
> + * dma-mapping: provide a generic dma-noncoherent implementation)"
> + *
> + * | map == for_device | unmap == for_cpu
> + * |----------------------------------------------------------------
> + * TO_DEV | writeback writeback | none none
> + * FROM_DEV | invalidate invalidate | invalidate* invalidate*
> + * BIDIR | writeback+inv writeback+inv | invalidate invalidate
> + *
> + * [*] needed for CPU speculative prefetches
> + *
> + * NOTE: we don't check the validity of direction argument as it is done in
> + * upper layer functions (in include/linux/dma-mapping.h)
> + */
> +
> void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
> size_t size, enum dma_data_direction dir)
> {
> - dma_cache_wback(paddr, size);
> + switch (dir) {
> + case DMA_TO_DEVICE:
> + dma_cache_wback(paddr, size);
> + break;
> +
> + case DMA_FROM_DEVICE:
> + dma_cache_inv(paddr, size);
> + break;
> +
> + case DMA_BIDIRECTIONAL:
> + dma_cache_wback_inv(paddr, size);
> + break;
> +
> + default:
> + break;
> + }
> }
>
> void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
> size_t size, enum dma_data_direction dir)
> {
> - dma_cache_inv(paddr, size);
> + switch (dir) {
> + case DMA_TO_DEVICE:
> + break;
> +
> + /* FROM_DEVICE invalidate needed if speculative CPU prefetch only */
> + case DMA_FROM_DEVICE:
> + case DMA_BIDIRECTIONAL:
> + dma_cache_inv(paddr, size);
> + break;
> +
> + default:
> + break;
> + }
> }
>
>
