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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Date:   Tue, 30 Jan 2018 14:25:45 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Benjamin GAIGNARD <benjamin.gaignard@...com>
Cc:     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>,
        Benjamin Gaignard <benjamin.gaignard@...aro.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

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.

>> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
>> index af4c752..8dfbe61 100644
>> --- a/drivers/firmware/qcom_scm.c
>> +++ b/drivers/firmware/qcom_scm.c
>> @@ -448,7 +448,7 @@ int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t
>> mem_sz,
>>       struct qcom_scm_mem_map_info *mem_to_map;
>>       phys_addr_t mem_to_map_phys;
>>       phys_addr_t dest_phys;
>> -     phys_addr_t ptr_phys;
>> +     dma_addr_t ptr_phys;
>>       size_t mem_to_map_sz;
>>       size_t dest_sz;
>>       size_t src_sz;

This would be bad: you can basically never have a 'dma_addr_t ptr_phys': it can
be exactly one of 'dma address',  'physical address' or a pointer,
this claims that the
struct member is all three of them.

The proper fix here is to stop using dma_alloc_coherent.

     Arnd