linux-kernel - Re: [PATCH v5 5/6] ARM: dts: sun8i: a83t: Add MIPI CSI-2 controller node

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Message-ID: <YxC/3KLfJHpld+jx@pendragon.ideasonboard.com>
Date:   Thu, 1 Sep 2022 17:21:16 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v5 5/6] ARM: dts: sun8i: a83t: Add MIPI CSI-2 controller
 node

On Thu, Sep 01, 2022 at 04:04:40PM +0200, Paul Kocialkowski wrote:
> Hi Laurent,
> 
> On Fri 26 Aug 22, 21:59, Laurent Pinchart wrote:
> > Hi Paul,
> > 
> > Thank you for the patch.
> > 
> > On Fri, Aug 26, 2022 at 08:28:02PM +0200, Paul Kocialkowski wrote:
> > > MIPI CSI-2 is supported on the A83T with a dedicated controller that
> > > covers both the protocol and D-PHY. It can be connected to the CSI
> > > interface as a V4L2 subdev through the fwnode graph.
> > > 
> > > This is not done by default since connecting the bridge without a
> > > subdev attached to it will cause a failure on the CSI driver.
> > 
> > No urgency, but would it be possible to fix this so that the CSI-2
> > receiver can be connected to the CSI unconditionally in DT ? The
> > connection exists at the hardware level in the SoC, and should thus
> > exist here too, regardless of whether or not a sensor is connected.
> 
> Yes it's true that having the link always would be legitimate.
> 
> For the context, this CSI controller can be switched between the MIPI CSI-2
> controller and a parallel sensor input (i.e. it's not dedicated to one or the
> other like on the V3).
> 
> Last time I tried, having the connection between the two always there resulted
> in the unability to use a parallel sensor when no sensor is attached to the
> mipi csi-2 receiver. Probably because the async notifier never completes since
> the mipi csi-2's subdev is never registered without a sensor subdev attached.
> 
> Do you see a way to handle this case properly?

It sounds like an issue in the CSI-2 receiver driver. If there's no
input device attached to it, it should register its subdev directly,
without its own async notifier.

> > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> > > ---
> > >  arch/arm/boot/dts/sun8i-a83t.dtsi | 26 ++++++++++++++++++++++++++
> > >  1 file changed, 26 insertions(+)
> > > 
> > > diff --git a/arch/arm/boot/dts/sun8i-a83t.dtsi b/arch/arm/boot/dts/sun8i-a83t.dtsi
> > > index 82fdb04122ca..ecf9f3b2c0c0 100644
> > > --- a/arch/arm/boot/dts/sun8i-a83t.dtsi
> > > +++ b/arch/arm/boot/dts/sun8i-a83t.dtsi
> > > @@ -1064,6 +1064,32 @@ csi: camera@...0000 {
> > >  			status = "disabled";
> > >  		};
> > >  
> > > +		mipi_csi2: csi@...1000 {
> > > +			compatible = "allwinner,sun8i-a83t-mipi-csi2";
> > > +			reg = <0x01cb1000 0x1000>;
> > > +			interrupts = <GIC_SPI 83 IRQ_TYPE_LEVEL_HIGH>;
> > > +			clocks = <&ccu CLK_BUS_CSI>,
> > > +				 <&ccu CLK_CSI_SCLK>,
> > > +				 <&ccu CLK_MIPI_CSI>,
> > > +				 <&ccu CLK_CSI_MISC>;
> > > +			clock-names = "bus", "mod", "mipi", "misc";
> > > +			resets = <&ccu RST_BUS_CSI>;
> > > +			status = "disabled";
> > > +
> > > +			ports {
> > > +				#address-cells = <1>;
> > > +				#size-cells = <0>;
> > > +
> > > +				mipi_csi2_in: port@0 {
> > > +					reg = <0>;
> > > +				};
> > > +
> > > +				mipi_csi2_out: port@1 {
> > > +					reg = <1>;
> > > +				};
> > > +			};
> > > +		};
> > > +
> > >  		hdmi: hdmi@...0000 {
> > >  			compatible = "allwinner,sun8i-a83t-dw-hdmi";
> > >  			reg = <0x01ee0000 0x10000>;

-- 
Regards,

Laurent Pinchart