linux-kernel - Re: [PATCH] sparc32: Page align size in arch_dma

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Date:   Thu, 9 Sep 2021 08:07:12 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andreas Larsson <andreas@...sler.com>
Cc:     David Miller <davem@...emloft.net>, sparclinux@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        Sam Ravnborg <sam@...nborg.org>, linux-kernel@...r.kernel.org,
        software@...sler.com
Subject: Re: [PATCH] sparc32: Page align size in arch_dma_alloc

On Wed, Sep 08, 2021 at 09:48:22AM +0200, Andreas Larsson wrote:
> Commit 53b7670e5735 ("sparc: factor the dma coherent mapping into
> helper") lost the page align for the calls to dma_make_coherent and
> srmmu_unmapiorange. The latter cannot handle a non page aligned len
> argument.
> 
> Signed-off-by: Andreas Larsson <andreas@...sler.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@....de>

Andreas - while I've got your attention:  I've been looking into fully
converting sparc32 to the generic DMA code.  Do you have any
documentation for the Leon cache handling in dma_make_coherent,
and more importantly how that applies to the dma coherent handling?
I could see how a flush might be required for the streaming DMA mappings,
that is mapping normal cached memory for I/O.  But for the coherent
allocations which can be accessed from the device and the cpu without
another DMA mapping call this seems really strange.