linux-kernel - Re: [PATCH 2/2] media: s5p-mfc: fix MMAP of mfc buffer during reqbufs

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Date:   Mon, 27 Feb 2017 08:47:18 +0530
From:   "pankaj.dubey" <pankaj.dubey@...sung.com>
To:     Javier Martinez Canillas <javier@....samsung.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     kyungmin.park@...sung.com, jtp.park@...sung.com,
        mchehab@...nel.org, mchehab@....samsung.com,
        hans.verkuil@...co.com, krzk@...nel.org, kgene@...nel.org,
        Smitha T Murthy <smitha.t@...sung.com>
Subject: Re: [PATCH 2/2] media: s5p-mfc: fix MMAP of mfc buffer during reqbufs

Hello Javier,

On Saturday 25 February 2017 01:12 AM, Javier Martinez Canillas wrote:
> Hello Pankaj,
> 
> On 12/16/2016 08:48 AM, Pankaj Dubey wrote:
>> From: Smitha T Murthy <smitha.t@...sung.com>
>>
>> It has been observed on ARM64 based Exynos SoC, if IOMMU is not enabled
>> and we try to use reserved memory for MFC, reqbufs fails with below
>> mentioned error
>> ---------------------------------------------------------------------------
>> V4L2 Codec decoding example application
>> Kamil Debski <k.debski@...sung.com>
>> Copyright 2012 Samsung Electronics Co., Ltd.
>>
>> Opening MFC.
>> (mfc.c:mfc_open:58): MFC Info (/dev/video0): driver="s5p-mfc" \
>> bus_info="platform:12c30000.mfc0" card="s5p-mfc-dec" fd=0x4[
>> 42.339165] Remapping memory failed, error: -6
>>
>> MFC Open Success.
>> (main.c:main:711): Successfully opened all necessary files and devices
>> (mfc.c:mfc_dec_setup_output:103): Setup MFC decoding OUTPUT buffer \
>> size=4194304 (requested=4194304)
>> (mfc.c:mfc_dec_setup_output:120): Number of MFC OUTPUT buffers is 2 \
>> (requested 2)
>>
>> [App] Out buf phy : 0x00000000, virt : 0xffffffff
>> Output Length is = 0x300000
>> Error (mfc.c:mfc_dec_setup_output:145): Failed to MMAP MFC OUTPUT buffer
>> -------------------------------------------------------------------------
>> This is because the device requesting for memory is mfc0.left not the parent mfc0.
>> Hence setting of alloc_devs need to be done only if IOMMU is enabled
>> and in that case both the left and right device is treated as mfc0 only.
>>
> 
> I see, so likely you were facing the issue described in patch 1/2 after this
> patch since the driver doesn't set alloc_devs when IOMMU is disabled, right?
> 

Yes.

> In any case, I guess these patches have been superseded by Marek's series[0]
> so they are no longer needed?
> 

Yes, these patches have been superseded but now by Marek's series.
I missed to check Marek's series [0] due to some official assignment,
but we followed up our patch series with Marek, and fix was provided in
of_reserved_mem.c via patch [1] which has been accepted and merged as
well. I will try to find out some time and test Marek's patch series [0].

[1]: https://patchwork.kernel.org/patch/9482499/

Thanks,
Pankaj Dubey

> [0]: https://www.spinics.net/lists/linux-media/msg111156.html
> 
> Best regards,
>