Re: [PATCH v2 1/2] dt-bindings: i3c: MIPI I3C Host Controller Interface

From: Rob Herring <robh@kernel.org>
To: Nicolas Pitre <nico@fluxnic.net>
Cc: devicetree@vger.kernel.org, Robert Gough <robert.gough@intel.com>,
	Laura Nixon <laura.nixon@team.mipi.org>,
	Nicolas Pitre <npitre@baylibre.com>,
	Boris Brezillon <boris.brezillon@collabora.com>,
	Matthew Schnoor <matthew.schnoor@intel.com>,
	linux-i3c@lists.infradead.org
Subject: Re: [PATCH v2 1/2] dt-bindings: i3c: MIPI I3C Host Controller Interface
Date: Tue, 25 Aug 2020 15:29:32 -0600	[thread overview]
Message-ID: <20200825212932.GA1360264@bogus> (raw)
In-Reply-To: <20200819031723.1398378-2-nico@fluxnic.net>

On Tue, Aug 18, 2020 at 11:17:22PM -0400, Nicolas Pitre wrote:
> From: Nicolas Pitre <npitre@baylibre.com>
> 
> The MIPI I3C HCI (Host Controller Interface) specification defines
> a common software driver interface to support compliant MIPI I3C
> host controller hardware implementations from multiple vendors.
> 
> Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
> ---
>  .../devicetree/bindings/i3c/mipi-i3c-hci.yaml | 41 +++++++++++++++++++
>  1 file changed, 41 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/i3c/mipi-i3c-hci.yaml
> 
> diff --git a/Documentation/devicetree/bindings/i3c/mipi-i3c-hci.yaml b/Documentation/devicetree/bindings/i3c/mipi-i3c-hci.yaml
> new file mode 100644
> index 0000000000..8fc18ea922
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i3c/mipi-i3c-hci.yaml
> @@ -0,0 +1,41 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/i3c/mipi-i3c-hci.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: MIPI I3C HCI Device Tree Bindings
> +
> +maintainers:
> +  - Nicolas Pitre <npitre@baylibre.com>
> +
> +description: |
> +  MIPI I3C Host Controller Interface
> +
> +  The MIPI I3C HCI (Host Controller Interface) specification defines
> +  a common software driver interface to support compliant MIPI I3C
> +  host controller hardware implementations from multiple vendors.
> +
> +  For details, please see:
> +  https://www.mipi.org/specifications/i3c-hci
> +
> +properties:
> +  compatible:
> +    const: mipi-i3c-hci

What about my comments on v1? Pasted again:

A register interface (or protocol) spec is never complete enough to
capture all the details about a specific h/w implementation. One just
has to go look at AHCI, EHCI, OHCI, XHCI, UFS, 8250, etc. bindings.
Let's not start with pretending that here. Fine for this to be a
fallback, but it must have a compatible for a specific implementation.

Also, which version of the spec does this compatible correspond to? Or
are there not HCI differences in the spec versions you mention in the
cover letter?

> +  reg:
> +    maxItems: 1
> +  interrupts:
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +
> +examples:
> +  - |
> +    mipi_i3c_hci@a0000000 {

i3c@a0000000

> +      compatible = "mipi-i3c-hci";
> +      reg = <0xa0000000 0x2000>;
> +      interrupts = <89>;
> +    };
> -- 
> 2.26.2
> 

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