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Subject: Re: [PATCH 0/2] Follow-up patches for Cedrus v9
To:     Chen-Yu Tsai <wens@csie.org>
Cc:     Paul Kocialkowski <contact@paulk.fr>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Linux Media Mailing List <linux-media@vger.kernel.org>,
        devel@driverdev.osuosl.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-sunxi <linux-sunxi@googlegroups.com>,
        Randy Li <ayaka@soulik.info>, ezequiel@collabora.com,
        Tomasz Figa <tfiga@chromium.org>,
        Alexandre Courbot <acourbot@chromium.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
References: <20180907163347.32312-1-contact@paulk.fr>
 <11104c03-97ac-8b36-7d75-dfecb8fcce10@xs4all.nl>
 <CAGb2v67F2a-kYFRb_f+CyhzkHf5+Y+h01=SE-rxJ=-Oj-ma1BA@mail.gmail.com>
From:   Hans Verkuil <hverkuil@xs4all.nl>
Message-ID: <3c4e5a98-4dbd-9a8c-8dab-612a923f0eb9@xs4all.nl>
Date:   Sat, 8 Sep 2018 13:24:13 +0200
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On 09/08/2018 12:22 PM, Chen-Yu Tsai wrote:
> On Sat, Sep 8, 2018 at 6:06 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>>
>> On 09/07/2018 06:33 PM, Paul Kocialkowski wrote:
>>> This brings the requested modifications on top of version 9 of the
>>> Cedrus VPU driver, that implements stateless video decoding using the
>>> Request API.
>>>
>>> Paul Kocialkowski (2):
>>>   media: cedrus: Fix error reporting in request validation
>>>   media: cedrus: Add TODO file with tasks to complete before unstaging
>>>
>>>  drivers/staging/media/sunxi/cedrus/TODO     |  7 +++++++
>>>  drivers/staging/media/sunxi/cedrus/cedrus.c | 15 ++++++++++++---
>>>  2 files changed, 19 insertions(+), 3 deletions(-)
>>>  create mode 100644 drivers/staging/media/sunxi/cedrus/TODO
>>>
>>
>> So close...
>>
>> When compiling under e.g. intel I get errors since it doesn't know about
>> the sunxi_sram_claim/release function and the PHYS_PFN_OFFSET define.
>>
>> Is it possible to add stub functions to linux/soc/sunxi/sunxi_sram.h
>> if CONFIG_SUNXI_SRAM is not defined? That would be the best fix for that.
>>
>> The use of PHYS_PFN_OFFSET is weird: are you sure this is the right
>> way? I see that drivers/of/device.c also sets dev->dma_pfn_offset, which
>> makes me wonder if this information shouldn't come from the device tree.
>>
>> You are the only driver that uses this define directly, which makes me
>> suspicious.
> 
> On Allwinner platforms, some devices do DMA directly on the memory BUS
> with the DRAM controller. In such cases, the DRAM has no offset. In all
> other cases where the DMA goes through the common system bus and the DRAM
> offset is either 0x40000000 or 0x20000000, depending on the SoC. Since the
> former case is not described in the device tree (this is being worked on
> by Maxime BTW), the dma_pfn_offset is not the value it should be. AFAIK
> only the display and media subsystems (VPU, camera, TS) are wired this
> way.
> 
> In drivers/gpu/drm/sun4i/sun4i_backend.c (the display driver) we use
> PHYS_OFFSET, which is pretty much the same thing.
>

OK, in that case just put #ifdef PHYS_PFN_OFFSET around that line together
with a comment that this will eventually come from the device tree.

Regards,

	Hans