linux-kernel - Re: [RFC PATCH v3 3/6] dt-binding: tegra: Add VI and CSI bindings

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Message-ID: <CAL_JsqKAVBS-KvP60Bv2JBQjUzTUgicx33nShn4enFpvysS9YA@mail.gmail.com>
Date:   Thu, 20 Feb 2020 13:45:56 -0600
From:   Rob Herring <robh@...nel.org>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Frank Chen <frankc@...dia.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Helen Koike <helen.koike@...labora.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        devicetree@...r.kernel.org, linux-clk <linux-clk@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 3/6] dt-binding: tegra: Add VI and CSI bindings

On Tue, Feb 18, 2020 at 9:28 PM Sowjanya Komatineni
<skomatineni@...dia.com> wrote:
>
>
> On 2/18/20 3:15 PM, Rob Herring wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On Fri, Feb 14, 2020 at 10:23:25AM -0800, Sowjanya Komatineni wrote:
> >> Tegra contains VI controller which can support up to 6 MIPI CSI
> >> camera sensors.
> >>
> >> Each Tegra CSI port from CSI unit can be one-to-one mapper to
> >> VI channel and can capture from an external camera sensor or
> >> from built-in test pattern generator.
> >>
> >> This patch adds dt-bindings for Tegra VI and CSI.
> >>
> >> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> >> ---
> >>   .../display/tegra/nvidia,tegra20-host1x.txt        | 55 ++++++++++++++++++----
> >>   1 file changed, 47 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.txt b/Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.txt
> >> index 9999255ac5b6..3d0ed540a646 100644
> >> --- a/Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.txt
> >> +++ b/Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.txt
> >> @@ -40,14 +40,24 @@ of the following host1x client modules:
> >>
> >>     Required properties:
> >>     - compatible: "nvidia,tegra<chip>-vi"
> >> -  - reg: Physical base address and length of the controller's registers.
> >> +  - reg: Physical base address and length of the controller registers.
> >>     - interrupts: The interrupt outputs from the controller.
> >> -  - clocks: Must contain one entry, for the module clock.
> >> +  - clocks: Must contain an entry for the module clock "vi"
> >>       See ../clocks/clock-bindings.txt for details.
> >>     - resets: Must contain an entry for each entry in reset-names.
> >>       See ../reset/reset.txt for details.
> >> -  - reset-names: Must include the following entries:
> >> -    - vi
> >> +  - reset-names: Must include the entry "vi"
> >> +
> >> +  Tegra210 has CSI part of VI sharing same host interface and register
> >> +  space. So, VI device node should have CSI child node.
> >> +
> >> +  - csi: mipi csi interface to vi
> >> +
> >> +    Required properties:
> >> +    - compatible: "nvidia,tegra<chip>-csi"
> >> +    - reg: Physical base address and length of the controller registers.
> >> +    - clocks: Must contain entries csi, cilab, cilcd, cile clocks.
> >> +      See ../clocks/clock-bindings.txt for details.
> >>
> >>   - epp: encoder pre-processor
> >>
> >> @@ -310,12 +320,41 @@ Example:
> >>                };
> >>
> >>                vi {
> >> -                     compatible = "nvidia,tegra20-vi";
> >> -                     reg = <0x54080000 0x00040000>;
> >> +                     compatible = "nvidia,tegra210-vi";
> >> +                     reg = <0x0 0x54080000 0x0 0x700>;
> >>                        interrupts = <0 69 0x04>;
> >> -                     clocks = <&tegra_car TEGRA20_CLK_VI>;
> >> -                     resets = <&tegra_car 100>;
> >> +                     assigned-clocks = <&tegra_car TEGRA210_CLK_VI>;
> >> +                     assigned-clock-parents = <&tegra_car TEGRA210_CLK_PLL_C4_OUT0>;
> >> +                     clocks = <&tegra_car TEGRA210_CLK_VI>;
> >> +                     clock-names = "vi";
> >> +                     resets = <&tegra_car 20>;
> >>                        reset-names = "vi";
> >> +
> >> +                     #address-cells = <2>;
> >> +                     #size-cells = <2>;
> >> +
> >> +                     ranges = <0x0 0x54080808 0x0 0x54080808 0x0 0x2000>;
> >> +
> >> +                     csi@...4080838 {
> > Drop '0x'
> Will fix in v4
> >
> >> +                             compatible = "nvidia,tegra210-csi";
> >> +                             reg = <0x0 0x54080838 0x0 0x2000>;
> > Kind of odd that this address and ranges address are not the same. And
> > also wrong that the size here exceeds the bounds of ranges.
> >
> > Also, best practice is to make the child address 0 or relative to the
> > parent.
>
> Actual CSI starts at offset 0x808 but we don't use couple of registers
> at offset 0x808.
>
> Will update ranges in v4 to start from 0x838 offset and will make child
> address relative to parent.

Seems odd, but okay. And you will never, ever need to use those
registers no matter what, and we can reject any DT change trying to
change it later?

Rob