Re: [PATCH v3] ata: sata_rcar: Fix DMA boundary mask

[Andy Shevchenko]

On Thu, Sep 17, 2020 at 4:12 PM Geert Uytterhoeven
<geert+renesas@xxxxxxxxx> wrote:
>
> 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.
>
> This also fixes the following WRITE DMA EXT timeout issue:
>
>     # dd if=/dev/urandom of=/mnt/de1/file1-1024M bs=1M count=1024
>     ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
>     ata1.00: failed command: WRITE DMA EXT
>     ata1.00: cmd 35/00:00:00:e6:0c/00:0a:00:00:00/e0 tag 0 dma 1310720 out
>     res 40/00:01:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
>     ata1.00: status: { DRDY }
>
> as seen by Shimoda-san since commit 429120f3df2dba2b ("block: fix
> splitting segments on boundary masks").
>
> Fixes: 8bfbeed58665dbbf ("sata_rcar: correct 'sata_rcar_sht'")
> Fixes: 9495b7e92f716ab2 ("driver core: platform: Initialize dma_parms for platform devices")
> Fixes: 429120f3df2dba2b ("block: fix splitting segments on boundary masks")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> Cc: stable <stable@xxxxxxxxxxxxxxx>
> ---
> v3:
>   - Add Reviewed-by, Tested-by,
>   - Augment description and Fixes: with Shimoda-san's problem report
>     https://lore.kernel.org/r/1600255098-21411-1-git-send-email-yoshihiro.shimoda.uh@xxxxxxxxxxx,
>
> v2:
>   - Add Reviewed-by, Tested-by, Cc.
> ---
>  drivers/ata/sata_rcar.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/ata/sata_rcar.c b/drivers/ata/sata_rcar.c
> index 141ac600b64c87ef..44b0ed8f6bb8a120 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_DTEND                        BIT(0)
>
> -#define SATA_RCAR_DMA_BOUNDARY         0x1FFFFFFEUL
> +#define SATA_RCAR_DMA_BOUNDARY         0x1FFFFFFFUL

Wondering if GENMASK() here will be better to avoid such mistakes.

>
>  /* Gen2 Physical Layer Control Registers */
>  #define RCAR_GEN2_PHY_CTL1_REG         0x1704
> --
> 2.17.1
>


-- 
With Best Regards,
Andy Shevchenko