stm32mp: add syscon for STGEN

Add STGEN as SYSCON device: allow access to device address
defined in device tree

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>

arch/arm/dts/stm32mp157-u-boot.dtsi

@@ -31,6 +31,13 @@
 	soc {
 		u-boot,dm-pre-reloc;
 	};
+
+	stgen: stgen@5C008000 {
+		compatible = "st,stm32-stgen";
+		reg = <0x5C008000 0x1000>;
+		status = "okay";
+		u-boot,dm-pre-reloc;
+	};
 };
 
 &clk_hsi {

arch/arm/mach-stm32mp/Makefile

@@ -6,5 +6,6 @@
 
 obj-y += cpu.o
 obj-y += dram_init.o
+obj-y += syscon.o
 
 obj-$(CONFIG_SPL_BUILD) += spl.o

arch/arm/mach-stm32mp/include/mach/stm32.h

@@ -25,6 +25,11 @@
 #define STM32_DDR_SIZE			SZ_1G
 
 #ifndef __ASSEMBLY__
+/* enumerated used to identify the SYSCON driver instance */
+enum {
+	STM32MP_SYSCON_UNKNOWN,
+	STM32MP_SYSCON_STGEN,
+};
 
 /*
  * enumerated for boot interface from Bootrom, used in TAMP_BOOT_CONTEXT

arch/arm/mach-stm32mp/syscon.c

@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2018, STMicroelectronics - All Rights Reserved
+ *
+ * SPDX-License-Identifier:	GPL-2.0+	BSD-3-Clause
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <syscon.h>
+#include <asm/arch/stm32.h>
+
+static const struct udevice_id stm32mp_syscon_ids[] = {
+	{ .compatible = "st,stm32-stgen",
+	  .data = STM32MP_SYSCON_STGEN },
+	{ }
+};
+
+U_BOOT_DRIVER(syscon_stm32mp) = {
+	.name = "stmp32mp_syscon",
+	.id = UCLASS_SYSCON,
+	.of_match = stm32mp_syscon_ids,
+	.bind = dm_scan_fdt_dev,
+};