linux-kernel - Re: [PATCH] nand: ranw: qcom_nand: stop using phys_to

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Message-ID: <CAK8P3a1M4v1hMduAX3y39DEjBiT=70xm-+qJ8CPLZHQwKOzJ1g@mail.gmail.com>
Date:   Wed, 11 Jul 2018 16:26:31 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Abhishek Sahu <absahu@...eaurora.org>,
        Archit Taneja <architt@...eaurora.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nand: ranw: qcom_nand: stop using phys_to_dma()

On Wed, Jul 11, 2018 at 3:04 PM, Boris Brezillon
<boris.brezillon@...tlin.com> wrote:
> On Wed, 11 Jul 2018 14:26:58 +0200
> Arnd Bergmann <arnd@...db.de> wrote:
>
>> Compile-testing this driver on x86 caused a link error:
>>
>> ERROR: "__phys_to_dma" [drivers/mtd/nand/raw/qcom_nandc.ko] undefined!
>>
>> The problem here is that the driver attempts to convert the physical
>> address into the DMA controller as a dma_addr_t and calls phys_to_dma()
>> to do the conversion.
>>
>> However, there is no generic way to convert a phys_addr_t into a dma_addr_t
>> for anything other than RAM (which should use the dma-mapping API instead).
>> The only correct use of phys_to_dma() instead is inside of the dma-mapping
>> implementation.
>
> Should we use dma_map_resource() to do the phys_addr_t to dma_addr_t
> conversion?

I had not seen that interface before, but yes, that does seem like the best
way to do it here.

       Arnd