linux-kernel - Re: [PATCH] scsi: ufs: core: Limit DMA alignment check

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Date:   Wed, 1 Feb 2023 09:20:39 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Asutosh Das <quic_asutoshd@...cinc.com>
Cc:     Bean Huo <beanhuo@...ron.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Jinyoung Choi <j-young.choi@...sung.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, mani@...nel.org
Subject: Re: [PATCH] scsi: ufs: core: Limit DMA alignment check

On 1/31/23 19:49, Bjorn Andersson wrote:
> The three DMA memory regions allocated for the host memory space is
> documented to require alignment of 128, 1024 and 1024 respectively, but
> the returned address is checked for PAGE_SIZE alignment.
> 
> In the case these allocations are serviced by e.g. the Arm SMMU, the
> size and alignment will be determined by its supported page sizes. In
> most cases SZ_4K and a few larger sizes are available.
> 
> In the typical configuration this does not cause problems, but in the
> event that the system PAGE_SIZE is increased beyond 4k, it's no longer
> reasonable to expect that the allocation will be PAGE_SIZE aligned.
> 
> Limit the DMA alignment check to the actual alignment requirements
> written in the comments in the code, to avoid the UFS core refusing to
> initialize with such configuration.

Reviewed-by: Bart Van Assche <bvanassche@....org>