Re: [PATCH 1/2] dt-bindings: media: sun4i-csi: Drop the module clock

[Chen-Yu Tsai <wens@csie.org>]

On Fri, Oct 4, 2019 at 12:37 AM Maxime Ripard <mripard@kernel.org> wrote:
>
> Hi,
>
> On Thu, Oct 03, 2019 at 11:51:05PM +0800, Chen-Yu Tsai wrote:
> > On Thu, Oct 3, 2019 at 11:48 PM Maxime Ripard <mripard@kernel.org> wrote:
> > >
> > > It turns out that what was thought to be the module clock was actually the
> > > clock meant to be used by the sensor, and isn't playing any role with the
> > > CSI controller itself. Let's drop that clock from our binding.
> > >
> > > Fixes: c5e8f4ccd775 ("media: dt-bindings: media: Add Allwinner A10 CSI binding")
> > > Reported-by: Chen-Yu Tsai <wens@csie.org>
> > > Signed-off-by: Maxime Ripard <mripard@kernel.org>
> > > ---
> > >  .../devicetree/bindings/media/allwinner,sun4i-a10-csi.yaml | 7 ++-----
> > >  1 file changed, 2 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/media/allwinner,sun4i-a10-csi.yaml b/Documentation/devicetree/bindings/media/allwinner,sun4i-a10-csi.yaml
> > > index 5dd1cf490cd9..d3e423fcb6c2 100644
> > > --- a/Documentation/devicetree/bindings/media/allwinner,sun4i-a10-csi.yaml
> > > +++ b/Documentation/devicetree/bindings/media/allwinner,sun4i-a10-csi.yaml
> > > @@ -27,14 +27,12 @@ properties:
> > >    clocks:
> > >      items:
> > >        - description: The CSI interface clock
> > > -      - description: The CSI module clock
> > >        - description: The CSI ISP clock
> > >        - description: The CSI DRAM clock
> > >
> > >    clock-names:
> > >      items:
> > >        - const: bus
> > > -      - const: mod
> > >        - const: isp
> > >        - const: ram
> > >
> > > @@ -89,9 +87,8 @@ examples:
> > >          compatible = "allwinner,sun7i-a20-csi0";
> > >          reg = <0x01c09000 0x1000>;
> > >          interrupts = <GIC_SPI 42 IRQ_TYPE_LEVEL_HIGH>;
> > > -        clocks = <&ccu CLK_AHB_CSI0>, <&ccu CLK_CSI0>,
> > > -                 <&ccu CLK_CSI_SCLK>, <&ccu CLK_DRAM_CSI0>;
> > > -        clock-names = "bus", "mod", "isp", "ram";
> > > +        clocks = <&ccu CLK_AHB_CSI0>, <&ccu CLK_CSI_SCLK>, <&ccu CLK_DRAM_CSI0>;
> > > +        clock-names = "bus", "isp", "ram";
> >
> > I believe what we thought was the ISP clock is actually the module clock
> > for the whole CSI subsystem. So we should still use the module clock entry,
> > and remove the ISP entry.
>
> I'm really not sure it is. CSI1 on the A20 (possibly the A10 as well,
> I haven't checked), and the one on the A13 don't have any ISP embedded
> in the CSI controller.
>
> It makes some difference, because according to the BSP, you can see
> that the ISP clock is taken for CSI0:
> https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.4/drivers/media/video/sun4i_csi/csi0/sun4i_drv_csi.c#L389
>
> While for CSI1, that block is commented out, and the ISP clock never
> used:
> https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.4/drivers/media/video/sun4i_csi/csi1/sun4i_drv_csi.c#L396
>
> So I really believe that the ISP clock is here to feed the ISP block
> within the CSI controller if there's any. But it's far from always the
> case, as opposed to a module clock for the whole CSI controller that
> would be here in both cases.

I guess we should try to test this with CSI1 one, either on a Cubieboard
or OlinuXino with a simple camera like the OV7670?

Do you have any hardware on hand for this? I have the Cubieboard but I
need to get some proper 2.0mm connector blocks.

ChenYu

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