Re: [PATCH 1/8] dt-bindings: stm32: add bindings for ML-AHB interconnect

From: Rob Herring <robh@kernel.org>
To: Fabien Dessenne <fabien.dessenne@st.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Ohad Ben-Cohen <ohad@wizery.com>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	devicetree@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-remoteproc@vger.kernel.org,
	Loic Pallardy <loic.pallardy@st.com>,
	Arnaud Pouliquen <arnaud.pouliquen@st.com>,
	Ludovic Barre <ludovic.barre@st.com>,
	Benjamin Gaignard <benjamin.gaignard@st.com>
Subject: Re: [PATCH 1/8] dt-bindings: stm32: add bindings for ML-AHB interconnect
Date: Wed, 27 Mar 2019 18:07:22 -0500	[thread overview]
Message-ID: <20190327230722.GA13708@bogus> (raw)
In-Reply-To: <1551795849-13672-2-git-send-email-fabien.dessenne@st.com>

On Tue, Mar 05, 2019 at 03:24:02PM +0100, Fabien Dessenne wrote:
> Document the ML-AHB interconnect for stm32 SoCs.
> 
> Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
> ---
>  .../devicetree/bindings/arm/stm32/mlahb.txt        | 30 ++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/stm32/mlahb.txt
> 
> diff --git a/Documentation/devicetree/bindings/arm/stm32/mlahb.txt b/Documentation/devicetree/bindings/arm/stm32/mlahb.txt
> new file mode 100644
> index 0000000..880cb38
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/stm32/mlahb.txt
> @@ -0,0 +1,30 @@
> +ML-AHB interconnect bindings
> +
> +These bindings describe the STM32 SoCs ML-AHB interconnect bus which connects
> +a Cortex-M subsystem with dedicated memories.
> +
> +Required properties:
> +- compatible: should be "simple-bus"

A binding for simple-bus was the first thing that looked odd.

> +- ranges: describes memory addresses translation between the local CPU and the
> +	   remote Cortex-M processor. Each memory region, is declared with 3
> +	   parameters:
> +		 - param 1: device base address (Cortex-M processor address)
> +		 - param 2: physical base address (local CPU address)
> +		 - param 3: size of the memory region.

Given that the driver is parsing ranges itself, this looks like abuse of 
ranges.

What exactly is address 0 supposed to be here? If it is the M4's view of 
memory, then dma-ranges is what you want to use here.

> +
> +The Cortex-M remote processor accessed via the mlahb interconnect is described
> +by a child node.
> +
> +Example:
> +mlahb: mlahb@0 {

Note that the unit-address is wrong here as it should be 38000000.

> +	compatible = "simple-bus";
> +	#address-cells = <1>;
> +	#size-cells = <1>;
> +	ranges = <0x00000000 0x38000000 0x10000>,
> +		 <0x10000000 0x10000000 0x60000>,
> +		 <0x30000000 0x30000000 0x60000>;
> +
> +	m4_rproc: m4@0 {
> +		...
> +	};
> +};
> -- 
> 2.7.4
> 