linux-kernel - Re: [PATCH v2 1/3] media: V3s: Add support for Allwinner CSI.

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Message-Id: <20170731084744.3d8d9f632858241c54efd185@magewell.com>
Date:   Mon, 31 Jul 2017 08:47:44 +0800
From:   Yong <yong.deng@...ewell.com>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Baruch Siach <baruch@...s.co.il>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Chen-Yu Tsai <wens@...e.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Hans Verkuil <hverkuil@...all.nl>,
        Arnd Bergmann <arnd@...db.de>,
        Hugues Fruchet <hugues.fruchet@...com>,
        Yannick Fertre <yannick.fertre@...com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Benoit Parrot <bparrot@...com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Jean-Christophe Trotin <jean-christophe.trotin@...com>,
        Ramesh Shanmugasundaram <ramesh.shanmugasundaram@...renesas.com>,
        Minghsiu Tsai <minghsiu.tsai@...iatek.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v2 1/3] media: V3s: Add support for Allwinner CSI.

On Thu, 27 Jul 2017 14:25:51 +0200
Maxime Ripard <maxime.ripard@...e-electrons.com> wrote:

> On Thu, Jul 27, 2017 at 03:16:44PM +0300, Baruch Siach wrote:
> > Hi Yong,
> > 
> > I managed to get the Frame Done interrupt with the previous version of this 
> > driver on the A33 OLinuXino. No data yet (all zeros). I'm still working on it.
> > 
> > One comment below.
> > 
> > On Thu, Jul 27, 2017 at 01:01:35PM +0800, Yong Deng wrote:
> > > Allwinner V3s SoC have two CSI module. CSI0 is used for MIPI interface
> > > and CSI1 is used for parallel interface. This is not documented in
> > > datasheet but by testing and guess.
> > > 
> > > This patch implement a v4l2 framework driver for it.
> > > 
> > > Currently, the driver only support the parallel interface. MIPI-CSI2,
> > > ISP's support are not included in this patch.
> > > 
> > > Signed-off-by: Yong Deng <yong.deng@...ewell.com>
> > > ---
> > 
> > [...]
> > 
> > > +static int update_buf_addr(struct sun6i_csi *csi, dma_addr_t addr)
> > > +{
> > > +	struct sun6i_csi_dev *sdev = sun6i_csi_to_dev(csi);
> > > +	/* transform physical address to bus address */
> > > +	dma_addr_t bus_addr = addr - 0x40000000;
> > 
> > What is the source of this magic number? Is it platform dependent? Are there 
> > other devices doing DMA that need this adjustment?
> 
> This is the RAM base address in most (but not all) Allwinner
> SoCs. You'll want to use PHYS_OFFSET instead.

I have try to use PHYS_OFFSET. But I found it is not 0x40000000. I will
try it again.

> 
> Maxime
> 
> -- 
> Maxime Ripard, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com


Thanks,
Yong