ram: rockchip: Add basic support for RK3528

Add support for reading DRAM size information from PMUGRF os_reg18 reg.

Compared to most Rockchip SoCs the RK3528 use os_reg18 for DRAM info,
instead of os_reg2.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

drivers/ram/rockchip/Makefile

@@ -13,6 +13,7 @@ obj-$(CONFIG_ROCKCHIP_RK3288) = sdram_rk3288.o
 obj-$(CONFIG_ROCKCHIP_RK3308) = sdram_rk3308.o
 obj-$(CONFIG_ROCKCHIP_RK3328) = sdram_rk3328.o sdram_pctl_px30.o sdram_phy_px30.o
 obj-$(CONFIG_ROCKCHIP_RK3399) += sdram_rk3399.o
+obj-$(CONFIG_ROCKCHIP_RK3528) += sdram_rk3528.o
 obj-$(CONFIG_ROCKCHIP_RK3568) += sdram_rk3568.o
 obj-$(CONFIG_ROCKCHIP_RK3588) += sdram_rk3588.o
 obj-$(CONFIG_ROCKCHIP_RV1126) += sdram_rv1126.o sdram_pctl_px30.o

drivers/ram/rockchip/sdram_rk3528.c

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright Contributors to the U-Boot project.
+
+#include <dm.h>
+#include <ram.h>
+#include <asm/arch-rockchip/sdram.h>
+
+#define PMUGRF_BASE			0xff370000
+#define OS_REG18_REG			0x248
+
+static int rk3528_dmc_get_info(struct udevice *dev, struct ram_info *info)
+{
+	info->base = CFG_SYS_SDRAM_BASE;
+	info->size = rockchip_sdram_size(PMUGRF_BASE + OS_REG18_REG);
+
+	return 0;
+}
+
+static struct ram_ops rk3528_dmc_ops = {
+	.get_info = rk3528_dmc_get_info,
+};
+
+static const struct udevice_id rk3528_dmc_ids[] = {
+	{ .compatible = "rockchip,rk3528-dmc" },
+	{ }
+};
+
+U_BOOT_DRIVER(rockchip_rk3528_dmc) = {
+	.name = "rockchip_rk3528_dmc",
+	.id = UCLASS_RAM,
+	.of_match = rk3528_dmc_ids,
+	.ops = &rk3528_dmc_ops,
+};