[RFC PATCH 1/1] soc: renesas: rcar-rst: Add support to set rproc boot address

[Julien Massot <julien.massot@iot.bzh>]

R-Car Gen3 SoC series has a realtime processor, the boot
address of this processor can be set thanks to CR7BAR register
of the reset module.

Export this function so that it's possible to set the boot
address from a remoteproc driver.

Also drop the __initdata qualifier on rcar_rst_base,
since we will use this address later than init time.

Signed-off-by: Julien Massot <julien.massot@iot.bzh>
---
 drivers/soc/renesas/rcar-rst.c       | 28 +++++++++++++++++++++++++++-
 include/linux/soc/renesas/rcar-rst.h |  2 ++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/renesas/rcar-rst.c b/drivers/soc/renesas/rcar-rst.c
index 8a1e402ea799..7f8452b07cdf 100644
--- a/drivers/soc/renesas/rcar-rst.c
+++ b/drivers/soc/renesas/rcar-rst.c
@@ -12,6 +12,8 @@
 
 #define WDTRSTCR_RESET		0xA55A0002
 #define WDTRSTCR		0x0054
+#define CR7BAR			0x0070
+#define CR7BAREN		BIT(4)
 
 static int rcar_rst_enable_wdt_reset(void __iomem *base)
 {
@@ -76,7 +78,7 @@ static const struct of_device_id rcar_rst_matches[] __initconst = {
 	{ /* sentinel */ }
 };
 
-static void __iomem *rcar_rst_base __initdata;
+static void __iomem *rcar_rst_base;
 static u32 saved_mode __initdata;
 
 static int __init rcar_rst_init(void)
@@ -130,3 +132,27 @@ int __init rcar_rst_read_mode_pins(u32 *mode)
 	*mode = saved_mode;
 	return 0;
 }
+
+/*
+ * Most of R-Car Gen3 SoCs have an ARM Realtime Core.
+ * Firmware boot address can be set before starting,
+ * the realtime core thanks to CR7BAR register.
+ * Boot address is on 32bit, and should be aligned on
+ * 4k boundary.
+ */
+int rcar_rst_set_rproc_boot_addr(u32 boot_addr)
+{
+	if (!rcar_rst_base)
+		return -EIO;
+
+	if (boot_addr % SZ_4K) {
+		pr_warn("Invalid boot address for remote processor, should be aligned on 4k\n");
+		boot_addr -= boot_addr % SZ_4K;
+	}
+
+	boot_addr |= CR7BAREN;
+	iowrite32(boot_addr, rcar_rst_base + CR7BAR);
+
+	return 0;
+}
+EXPORT_SYMBOL(rcar_rst_set_rproc_boot_addr);
diff --git a/include/linux/soc/renesas/rcar-rst.h b/include/linux/soc/renesas/rcar-rst.h
index 7899a5b8c247..7c97c2c4bba6 100644
--- a/include/linux/soc/renesas/rcar-rst.h
+++ b/include/linux/soc/renesas/rcar-rst.h
@@ -4,8 +4,10 @@
 
 #ifdef CONFIG_RST_RCAR
 int rcar_rst_read_mode_pins(u32 *mode);
+int rcar_rst_set_rproc_boot_addr(u32 boot_addr);
 #else
 static inline int rcar_rst_read_mode_pins(u32 *mode) { return -ENODEV; }
+static inline int rcar_rst_set_rproc_boot_addr(u32 boot_addr) { return -ENODEV; }
 #endif
 
 #endif /* __LINUX_SOC_RENESAS_RCAR_RST_H__ */
-- 
2.31.1