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

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Date:   Fri, 16 Oct 2020 09:32:46 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christoph Hellwig <hch@....de>, Ming Lei <ming.lei@...hat.com>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        linux-ide@...r.kernel.org,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        "Lad, Prabhakar" <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v3] ata: sata_rcar: Fix DMA boundary mask

On 10/15/20 12:34 PM, Geert Uytterhoeven wrote:
> Hi Jens,
> 
> On Thu, Sep 17, 2020 at 3:09 PM Geert Uytterhoeven
> <geert+renesas@...der.be> 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@...der.be>
>> Reviewed-by: Christoph Hellwig <hch@....de>
>> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Reviewed-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
>> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
>> Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>> Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
>> Cc: stable <stable@...r.kernel.org>
> 
> Can you please apply this patch?
> This is a fix for a regression in v5.7-rc5, and was first posted almost
> 5 months ago.

Applied, sorry that got missed.

-- 
Jens Axboe