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

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Date:   Wed, 29 Mar 2023 11:58:59 +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.
> 
> 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>;

Per "vMPM register map" in the driver, the slice size should be 0x44
instead of 0x48.  Is there one register missing from the driver
comment?

PS. It seems the "n" formula in the driver comment should be corrected
as below.

  n = DIV_ROUND_UP(pin_cnt, 32) - 1

Shawn

> 			};
> 		};
> 	};
> };