RE: [PATCH] ata: sata_rcar: Fix DMA boundary mask

[Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>]

Hi Geert,

Thank you for the patch.

> -----Original Message-----
> From: linux-ide-owner@vger.kernel.org <linux-ide-owner@vger.kernel.org> On Behalf Of Geert Uytterhoeven <geert+renesas@glider.be>
> Sent: 13 May 2020 12:04
> To: Jens Axboe <axboe@kernel.dk>; Ulf Hansson <ulf.hansson@linaro.org>; Greg Kroah-Hartman <gregkh@linuxfoundation.org>;
> Christoph Hellwig <hch@lst.de>
> Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>; linux-ide@vger.kernel.org; linux-renesas-soc@vger.kernel.org; linux-
> scsi@vger.kernel.org; linux-kernel@vger.kernel.org; Geert Uytterhoeven <geert+renesas@glider.be>
> Subject: [PATCH] ata: sata_rcar: Fix DMA boundary mask
>
> Before commit 9495b7e92f716ab2 ("driver core: platform: Initialize
> dma_parms for platform devices"), the R-Car SATA device didn't have DMA
> parameters.  Hence the DMA boundary mask supplied by its driver was
> silently ignored, as __scsi_init_queue() doesn't check the return value
> of dma_set_seg_boundary(), and the default value of 0xffffffff was used.
>
> Now the device has gained DMA parameters, the driver-supplied value is
> used, and the following warning is printed on Salvator-XS:
>
>     DMA-API: sata_rcar ee300000.sata: mapping sg segment across boundary [start=0x00000000ffffe000] [end=0x00000000ffffefff]
> [boundary=0x000000001ffffffe]
>     WARNING: CPU: 5 PID: 38 at kernel/dma/debug.c:1233 debug_dma_map_sg+0x298/0x300
>
> (the range of start/end values depend on whether IOMMU support is
>  enabled or not)
>
> The issue here is that SATA_RCAR_DMA_BOUNDARY doesn't have bit 0 set, so
> any typical end value, which is odd, will trigger the check.
>
> Fix this by increasing the DMA boundary value by 1.
>
> Fixes: 8bfbeed58665dbbf ("sata_rcar: correct 'sata_rcar_sht'")
> Fixes: 9495b7e92f716ab2 ("driver core: platform: Initialize dma_parms for platform devices")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> As by default the DMA debug code prints the first error only, this issue
> may be hidden on plain v5.7-rc5, where the FCP driver triggers a similar
> warning.  Merging commit dd844fb8e50b12e6 ("media: platform: fcp: Set
> appropriate DMA parameters") from the media tree fixes the FCP issue,
> and exposes the SATA issue.
>
> I added the second fixes tag because that commit is already being
> backported to stable kernels, and this patch thus needs backporting,
> too.
> ---
>  drivers/ata/sata_rcar.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
Without this patch I see SATA link being reset while doing a dd (dd if=/dev/urandom of=random-data bs=1M count=1000)

Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

Cheers,
Prabhakar

> diff --git a/drivers/ata/sata_rcar.c b/drivers/ata/sata_rcar.c
> index 980aacdbcf3b42b9..752db75b611e8f8a 100644
> --- a/drivers/ata/sata_rcar.c
> +++ b/drivers/ata/sata_rcar.c
> @@ -120,7 +120,7 @@
>  /* Descriptor table word 0 bit (when DTA32M = 1) */
>  #define SATA_RCAR_DTENDBIT(0)
>
> -#define SATA_RCAR_DMA_BOUNDARY0x1FFFFFFEUL
> +#define SATA_RCAR_DMA_BOUNDARY0x1FFFFFFFUL
>
>  /* Gen2 Physical Layer Control Registers */
>  #define RCAR_GEN2_PHY_CTL1_REG0x1704
> --
> 2.17.1
>



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