linux-kernel - Re: [PATCH] arm64: do not set dma masks that device connection can't handle

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Message-ID: <5c4736a6-4d0b-342e-2a5c-9aaaa933b138@cogentembedded.com>
Date:   Mon, 9 Jan 2017 09:56:34 +0300
From:   Nikita Yushchenko <nikita.yoush@...entembedded.com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Arnd Bergmann <arnd@...db.de>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Simon Horman <horms@...ge.net.au>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        artemi.ivanov@...entembedded.com
Subject: Re: [PATCH] arm64: do not set dma masks that device connection can't
 handle

>> +    if (mask > dev->archdata.parent_dma_mask)
>> +        mask = dev->archdata.parent_dma_mask;
>> +
>> +
> 
>    One empty line is enough...

Ok

>> +    /*
>> +     * Whatever the parent bus can set. A device must not set
>> +     * a DMA mask larger than this.
>> +     */
>> +    dev->archdata.parent_dma_mask = size;
> 
>    Not 'size - 1'?

Good question.

Indeed of_dma_configure() calls arch_setup_dma_ops() with size, not
mask. Which implies '-1' is needed here. Although better fix may be to
change caller side - to make DMA_BIT_MASK(64) case cleaner.

Will repost path.

Nikita