linux-kernel - [PATCH v2 3/5] ARM: dts: bcm2711: Add reserved memory template to hold firmware configuration

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Date:   Fri, 18 Dec 2020 16:43:18 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     srinivas.kandagatla@...aro.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     linux-arm-kernel@...ts.infradead.org, linux@...linux.org.uk,
        catalin.marinas@....com, will@...nel.org,
        devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com, tim.gover@...pberrypi.com,
        phil@...pberrypi.com
Subject: [PATCH v2 3/5] ARM: dts: bcm2711: Add reserved memory template to hold firmware configuration

RPi4's co-processor will copy the board's bootloader[1] configuration
into memory for the OS to consume. Specifically, for the bootloader
configuration and upgrade user-space routines to query it through
nvmem's sysfs interface.

Introduce a reserved-memory area template for the co-processor to edit
before booting the system so as for Linux not to overwrite that memory
and to expose it as an nvmem device.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>

[1] https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2711_bootloader_config.md
---

Changes since v1:
 - Introduce compatible string
 - Change alias name to something more explicit

 arch/arm/boot/dts/bcm2711-rpi-4-b.dts | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
index 403bacf986eb..3b4ab947492a 100644
--- a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
+++ b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
@@ -25,6 +25,7 @@ aliases {
 		emmc2bus = &emmc2bus;
 		ethernet0 = &genet;
 		pcie0 = &pcie0;
+		blconfig = &blconfig;
 	};
 
 	leds {
@@ -218,6 +219,22 @@ &pwm1 {
 	status = "okay";
 };
 
+&rmem {
+	/*
+	 * RPi4's co-processor will copy the board's bootloader configuration
+	 * into memory for the OS to consume. It'll also update this node with
+	 * its placement information.
+	 */
+	blconfig: nvram@0 {
+		compatible = "raspberrypi,bootloader-config", "nvmem-rmem";
+		#address-cells = <1>;
+		#size-cells = <1>;
+		reg = <0x0 0x0 0x0>;
+		no-map;
+		status = "disabled";
+	};
+};
+
 /* SDHCI is used to control the SDIO for wireless */
 &sdhci {
 	#address-cells = <1>;
-- 
2.29.2