[RFC PATCH] ARM: aspeed: Add secure boot controller support

[Joel Stanley <joel@jms.id.au>]

This reads out the status of the secure boot controller and exposes it
in sysfs.

An example on a AST2600A3 QEmu model:

 # grep . /sys/bus/soc/devices/soc0/*
 /sys/bus/soc/devices/soc0/abr_image:0
 /sys/bus/soc/devices/soc0/family:AST2600
 /sys/bus/soc/devices/soc0/low_security_key:0
 /sys/bus/soc/devices/soc0/machine:Rainier 2U
 /sys/bus/soc/devices/soc0/otp_protected:0
 /sys/bus/soc/devices/soc0/revision:A3
 /sys/bus/soc/devices/soc0/secure_boot:1
 /sys/bus/soc/devices/soc0/serial_number:888844441234abcd
 /sys/bus/soc/devices/soc0/soc_id:05030303
 /sys/bus/soc/devices/soc0/uart_boot:1

Signed-off-by: Joel Stanley <joel@jms.id.au>
---
 arch/arm/boot/dts/aspeed-g6.dtsi    |  5 ++
 drivers/soc/aspeed/aspeed-socinfo.c | 71 +++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/arch/arm/boot/dts/aspeed-g6.dtsi b/arch/arm/boot/dts/aspeed-g6.dtsi
index ee171b3364fa..8f947ed47fc5 100644
--- a/arch/arm/boot/dts/aspeed-g6.dtsi
+++ b/arch/arm/boot/dts/aspeed-g6.dtsi
@@ -384,6 +384,11 @@ adc1: adc@1e6e9100 {
 				status = "disabled";
 			};
 
+			sbc: secure-boot-controller@1e6f2000 {
+				compatible = "aspeed,ast2600-sbc";
+				reg = <0x1e6f2000 0x1000>;
+			};
+
 			gpio0: gpio@1e780000 {
 				#gpio-cells = <2>;
 				gpio-controller;
diff --git a/drivers/soc/aspeed/aspeed-socinfo.c b/drivers/soc/aspeed/aspeed-socinfo.c
index 1ca140356a08..6fa0c891f3cb 100644
--- a/drivers/soc/aspeed/aspeed-socinfo.c
+++ b/drivers/soc/aspeed/aspeed-socinfo.c
@@ -9,6 +9,8 @@
 #include <linux/slab.h>
 #include <linux/sys_soc.h>
 
+static u32 security_status;
+
 static struct {
 	const char *name;
 	const u32 id;
@@ -74,6 +76,54 @@ static const char *siliconid_to_rev(u32 siliconid)
 	return "??";
 }
 
+#define SEC_STATUS		0x14
+#define ABR_IMAGE_SOURCE	BIT(13)
+#define OTP_PROTECTED		BIT(8)
+#define LOW_SEC_KEY		BIT(7)
+#define SECURE_BOOT		BIT(6)
+#define UART_BOOT		BIT(5)
+
+static ssize_t abr_image_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", !!(security_status & ABR_IMAGE_SOURCE));
+}
+static DEVICE_ATTR_RO(abr_image);
+
+static ssize_t low_security_key_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", !!(security_status & LOW_SEC_KEY));
+}
+static DEVICE_ATTR_RO(low_security_key);
+
+static ssize_t otp_protected_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", !!(security_status & OTP_PROTECTED));
+}
+static DEVICE_ATTR_RO(otp_protected);
+
+static ssize_t secure_boot_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", !!(security_status & SECURE_BOOT));
+}
+static DEVICE_ATTR_RO(secure_boot);
+
+static ssize_t uart_boot_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	/* Invert the bit, as 1 is boot from SPI/eMMC */
+	return sprintf(buf, "%d\n", !(security_status & UART_BOOT));
+}
+static DEVICE_ATTR_RO(uart_boot);
+
+static struct attribute *aspeed_attrs[] = {
+	&dev_attr_abr_image.attr,
+	&dev_attr_low_security_key.attr,
+	&dev_attr_otp_protected.attr,
+	&dev_attr_secure_boot.attr,
+	&dev_attr_uart_boot.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(aspeed);
+
 static int __init aspeed_socinfo_init(void)
 {
 	struct soc_device_attribute *attrs;
@@ -81,6 +131,7 @@ static int __init aspeed_socinfo_init(void)
 	struct device_node *np;
 	void __iomem *reg;
 	bool has_chipid = false;
+	bool has_sbe = false;
 	u32 siliconid;
 	u32 chipid[2];
 	const char *machine = NULL;
@@ -109,6 +160,20 @@ static int __init aspeed_socinfo_init(void)
 	}
 	of_node_put(np);
 
+	/* AST2600 only */
+	np = of_find_compatible_node(NULL, NULL, "aspeed,ast2600-sbc");
+	if (of_device_is_available(np)) {
+		void *base = of_iomap(np, 0);
+		if (!base) {
+			of_node_put(np);
+			return -ENODEV;
+		}
+		security_status = readl(base + SEC_STATUS);
+		has_sbe = true;
+		iounmap(base);
+		of_node_put(np);
+	}
+
 	attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
 	if (!attrs)
 		return -ENODEV;
@@ -135,6 +200,9 @@ static int __init aspeed_socinfo_init(void)
 		attrs->serial_number = kasprintf(GFP_KERNEL, "%08x%08x",
 						 chipid[1], chipid[0]);
 
+	if (has_sbe)
+		attrs->custom_attr_group = aspeed_groups[0];
+
 	soc_dev = soc_device_register(attrs);
 	if (IS_ERR(soc_dev)) {
 		kfree(attrs->soc_id);
@@ -148,6 +216,9 @@ static int __init aspeed_socinfo_init(void)
 			attrs->revision,
 			attrs->soc_id);
 
+	if (has_sbe && (security_status & SECURE_BOOT))
+		pr_info("AST2600 secure boot enabled\n");
+
 	return 0;
 }
 early_initcall(aspeed_socinfo_init);
-- 
2.33.0