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Date:   Thu, 5 Mar 2020 16:23:37 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        Greg KH <gregkh@linuxfoundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Haibo Chen <haibo.chen@nxp.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH v4 14/14] mmc: queue: create dev->dma_parms before call
 dma_set_max_seg_size()
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References: <1582100757-20683-1-git-send-email-haibo.chen@nxp.com> <1582100757-20683-9-git-send-email-haibo.chen@nxp.com> <CAPDyKFrR3oawA0o8KJ1ZEP41Ydb+-QWFbtxLua5TLemHybQ6QQ@mail.gmail.com> <20200304162844.GA11727@lst.de> <CACRpkdakLfH_bpU5W44HGZ8XBYGqNsH7B+zuVKs2AXuJLwDtPw@mail.gmail.com>
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On Thu, Mar 05, 2020 at 03:29:55PM +0100, Linus Walleij wrote:
> I agree. This relates to my reply to Greg K-H recently:
> https://lore.kernel.org/lkml/CACRpkdajhivkOkZ63v-hr7+6ObhTffYOx5uZP0P-MYvuVnyweA@mail.gmail.com/
> 
> The core of the problem is that drivers/of/platform.c is
> very simple and has no idea what kind of bus it is populating
> with devices from Device Tree. It is just guessing.
> 
> For example platform.c contains this:
> 
>         dev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
>         if (!dev->dev.dma_mask)
>                 dev->dev.dma_mask = &dev->dev.coherent_dma_mask;
> 
> And again part of the problem is that the device tree parser
> mostly just create struct platform_device's on the platform bus
> and has no real idea about any constraints on the bus where
> it will eventually end up after the platform device is probed and
> a new device on some other bus has been created.

the plaform device code should allocate the dma_params for every
device.  It should not set any limits in that, that is up to the
host drivers.