linux-kernel - Re: [PATCH 0/2] Resolve MPM register space situation

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Date:   Wed, 29 Mar 2023 11:34:24 +0800
From:   Shawn Guo <shawn.guo@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 0/2] Resolve MPM register space situation

On Tue, Mar 28, 2023 at 12:02:51PM +0200, Konrad Dybcio wrote:
> The MPM (and some other things, irrelevant to this patchset) resides
> (as far as the ARM cores are concerned, anyway) in a MMIO-mapped region
> that's a portion of the RPM (low-power management core)'s RAM, known
> as the RPM Message RAM. Representing this relation in the Device Tree
> creates some challenges, as one would either have to treat a memory
> region as a bus, map nodes in a way such that their reg-s would be
> overlapping, or supply the nodes with a slice of that region.
> 
> This series implements the third option, by adding a qcom,rpm-msg-ram
> property, which has been used for some drivers poking into this region
> before. Bindings ABI compatibility is preserved through keeping the
> "normal" (a.k.a read the reg property and map that region) way of
> passing the register space.

I have to admit that I wasn't aware of it, this message RAM is also
accessed by cores like modem, ADSP etc.  I agree in principle this is
a good change!

Shawn

> 
> Example representation with this patchset:
> 
> / {
> 	[...]
> 
> 	mpm: interrupt-controller {
> 		compatible = "qcom,mpm";
> 		qcom,rpm-msg-ram = <&apss_mpm>;
> 		[...]
> 	};
> 
> 	[...]
> 
> 	soc: soc@0 {
> 		[...]
> 
> 		rpm_msg_ram: sram@...0000 {
> 			compatible = "qcom,rpm-msg-ram", "mmio-sram";
> 			reg = <0 0x045f0000 0 0x7000>;
> 			#address-cells = <1>;
> 			#size-cells = <1>;
> 			ranges = <0 0x0 0x045f0000 0x7000>;
> 
> 			apss_mpm: sram@1b8 {
> 				reg = <0x1b8 0x48>;
> 			};
> 		};
> 	};
> };
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
> Konrad Dybcio (2):
>       dt-bindings: interrupt-controller: mpm: Allow passing reg through phandle
>       irqchip: irq-qcom-mpm: Support passing a slice of SRAM as reg space
> 
>  .../bindings/interrupt-controller/qcom,mpm.yaml    |  6 ++++-
>  drivers/irqchip/irq-qcom-mpm.c                     | 30 ++++++++++++++++++----
>  2 files changed, 30 insertions(+), 6 deletions(-)
> ---
> base-commit: a6faf7ea9fcb7267d06116d4188947f26e00e57e
> change-id: 20230328-topic-msgram_mpm-c688be3bc294
> 
> Best regards,
> -- 
> Konrad Dybcio <konrad.dybcio@...aro.org>
>