linux-kernel - Re: Compilation error report for: drivers/firmware/qcom_scm.c:469:47: error: passing argument 3 of ?dma_alloc

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Message-ID: <CA+M3ks6psojsyPze_o3A7eqUGg3AstJFqEptR2sQ6D6dNVougA@mail.gmail.com>
Date:   Sun, 4 Feb 2018 11:01:34 +0100
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Benjamin GAIGNARD <benjamin.gaignard@...com>,
        Arnaud POULIQUEN <arnaud.pouliquen@...com>,
        "Andy Gross <andy.gross@...aro.org> , David Brown" 
        <david.brown@...aro.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-soc@...r.kernel.org" <linux-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Compilation error report for: drivers/firmware/qcom_scm.c:469:47:
 error: passing argument 3 of ?dma_alloc_coherent? from incompatible pointer type

2018-02-03 0:29 GMT+01:00 Bjorn Andersson <bjorn.andersson@...aro.org>:
> On Tue 30 Jan 05:25 PST 2018, Arnd Bergmann wrote:
>
>> On Tue, Jan 30, 2018 at 11:11 AM, Benjamin GAIGNARD
>> <benjamin.gaignard@...com> wrote:
>> >
>> > On 01/12/2018 05:11 PM, Arnaud Pouliquen wrote:
>> >> Hello Andy,David,
>> > + Arnd
>> >
>> > I have the same issue on drm-misc-next.
>> > Does Arnaud's fix make sense or should we update/change the way of how
>> > we compile the kernel ?
>>
>> We've hit a couple of bugs with qcom drivers confusing physical addresses
>> and DMA addresses in the past, usually the drivers were buggy in
>> some form, and tried to use dma_alloc_coherent() to get a buffer
>> that gets passed into a firmware interface taking a physical address,
>> which is of course completely wrong.
>>
>
> Thanks Arnd, for once again using the words "bug" and "completely wrong"
> when referring to something that obviously works just fine...
>

I can't judge if using dma_alloc_coherent is correct or not here but, obviously,
the type of the third parameter doesn't match dma_alloc_coherent prototype.
May you consider to fix that ?


>
> The solution you introduced for venus and adreno relies on static
> reservations of system ram, which isn't pretty, but more importantly
> isn't viable for the qcom_scm driver.
>
>
> So, how do I dynamically allocate a chunk of coherent memory?
>
> Preferably with the possibility of unmapping it temporarily from Linux
> while passing the buffer into the trusted environment (as any accesses
> during the operation might cause access violations).
>
> Regards,
> Bjorn