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

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Message-ID: <231a408f-a696-baab-6eda-0d959689f476@cogentembedded.com>
Date:   Wed, 13 May 2020 15:43:51 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Jens Axboe <axboe@...nel.dk>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christoph Hellwig <hch@....de>
Cc:     linux-ide@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: sata_rcar: Fix DMA boundary mask

Hello!

On 13.05.2020 14:04, Geert Uytterhoeven 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.
> 
> 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@...der.be>

Reviewed-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>

    Sorry, my mistake that went undetected for many years. :-)

MBR, Sergei