linux-kernel - Re: [PATCH v2 2/3] arm64: dts: allwinner: a64: Add A64 CSI controller

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Date:   Fri, 7 Dec 2018 22:06:34 +0530
From:   Jagan Teki <jagan@...rulasolutions.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Michael Trimarchi <michael@...rulasolutions.com>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-amarula@...rulasolutions.com
Subject: Re: [PATCH v2 2/3] arm64: dts: allwinner: a64: Add A64 CSI controller

On Fri, Dec 7, 2018 at 1:17 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
>
> On Thu, Dec 06, 2018 at 06:07:59PM +0100, Michael Nazzareno Trimarchi wrote:
> > On Thu, Dec 6, 2018 at 4:34 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> > > On Thu, Dec 06, 2018 at 06:53:05PM +0530, Jagan Teki wrote:
> > > > Allwinner A64 CSI controller has similar features as like in
> > > > H3, So add support for A64 via H3 fallback.
> > > >
> > > > Also updated CSI_SCLK to use 300MHz via assigned-clocks, since
> > > > the default clock 600MHz seems unable to drive the sensor(ov5640)
> > > > to capture the image.
> > > >
> > > > Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>
> > > > ---
> > > > Changes for v2:
> > > > - Use CSI_SCLK to 300MHz
> > > >
> > > >  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 23 +++++++++++++++++++
> > > >  1 file changed, 23 insertions(+)
> > > >
> > > > diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> > > > index 384c417cb7a2..d7ab0006ebce 100644
> > > > --- a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> > > > +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> > > > @@ -532,6 +532,12 @@
> > > >                       interrupt-controller;
> > > >                       #interrupt-cells = <3>;
> > > >
> > > > +                     csi_pins: csi-pins {
> > > > +                             pins = "PE0", "PE2", "PE3", "PE4", "PE5", "PE6",
> > > > +                                    "PE7", "PE8", "PE9", "PE10", "PE11";
> > > > +                             function = "csi0";
> > > > +                     };
> > > > +
> > > >                       i2c0_pins: i2c0_pins {
> > > >                               pins = "PH0", "PH1";
> > > >                               function = "i2c0";
> > > > @@ -899,6 +905,23 @@
> > > >                       status = "disabled";
> > > >               };
> > > >
> > > > +             csi: csi@...0000 {
> > > > +                     compatible = "allwinner,sun50i-a64-csi",
> > > > +                                  "allwinner,sun8i-h3-csi";
> > > > +                     reg = <0x01cb0000 0x1000>;
> > > > +                     interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
> > > > +                     clocks = <&ccu CLK_BUS_CSI>,
> > > > +                              <&ccu CLK_CSI_SCLK>,
> > > > +                              <&ccu CLK_DRAM_CSI>;
> > > > +                     clock-names = "bus", "mod", "ram";
> > > > +                     resets = <&ccu RST_BUS_CSI>;
> > > > +                     pinctrl-names = "default";
> > > > +                     pinctrl-0 = <&csi_pins>;
> > > > +                     assigned-clocks = <&ccu CLK_CSI_SCLK>;
> > > > +                     assigned-clock-rates = <300000000>;
> > >
> > > That should be enforced in the driver.
> > >
> >
> > We are not really sure what is the best here. Our first idea was to
> > put in the board file and then Jagan
> > decide to put in dtsi. We don't have enough coverage of camera on this
> > CPU and I prefer to stay with this
> > minimal change that does not impact the driver.
>
> The thing is that:
>   - in this commit log, you're stating that it depends on the sensor,
>     which indicates that this would be a board level addition
>   - In another patch series, Jagan reported IIRC that it actually
>     depends on the resolution, so it doesn't belong in the DT at all
>   - And then, you don't even have any guarantee on the clock rate. The
>     sole guarantee you have is that when your driver will probe, the
>     rate will be close to those 300MHz. That's it. It might completely
>     change after the driver has probed, or be rounded to something
>     else entirely, who knows.

Let's to be clear.

- with default clock(600MHz) the sensor get probed but image capture
has an issue.
- with 300MHz the image capture working with 320x240@30, 640x480@30,
640x480@60, 1280x720@30 with UYVY8_2X8 and YUYV8_2X8 formats but
1080p@30 seems broken (the same I have mentioned in another mail)
- since all this is verified on ov5640, I have mentioned the same
thing on commit message for future reference.