linux-kernel - [PATCH 2/2] ARM: aspeed: Add secure boot controller support

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Message-Id: <20220201050501.182961-3-joel@jms.id.au>
Date:   Tue,  1 Feb 2022 15:35:01 +1030
From:   Joel Stanley <joel@....id.au>
To:     Arnd Bergmann <arnd@...db.de>, Andrew Jeffery <andrew@...id.au>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, Ryan Chen <ryan_chen@...eedtech.com>
Subject: [PATCH 2/2] ARM: aspeed: Add secure boot controller support

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

An example on a AST2600A3 QEMU model:

 # grep -r . /sys/firmware/bootinfo/*
 /sys/firmware/bootinfo/abr_image:0
 /sys/firmware/bootinfo/low_security_key:0
 /sys/firmware/bootinfo/otp_protected:0
 /sys/firmware/bootinfo/secure_boot:1
 /sys/firmware/bootinfo/uart_boot:0

On boot the state of the system according to the secure boot controller
will be printed:

 [    0.037634] AST2600 secure boot enabled

or

 [    0.037935] AST2600 secure boot disabled

The initialisation is changed from early_initcall to subsys_initcall
because we need the firmware_kobj to be initialised, and because there's
no requirement to print this information early.

Signed-off-by: Joel Stanley <joel@....id.au>
Reviewed-by: Ryan Chen <ryan_chen@...eedtech.com>
---
 drivers/soc/aspeed/aspeed-socinfo.c | 84 ++++++++++++++++++++++++++++-
 1 file changed, 83 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/aspeed/aspeed-socinfo.c b/drivers/soc/aspeed/aspeed-socinfo.c
index 1ca140356a08..fe77b31e4d1d 100644
--- a/drivers/soc/aspeed/aspeed-socinfo.c
+++ b/drivers/soc/aspeed/aspeed-socinfo.c
@@ -8,6 +8,9 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/sys_soc.h>
+#include <linux/firmware_bootinfo.h>
+
+static u32 security_status;
 
 static struct {
 	const char *name;
@@ -74,6 +77,83 @@ 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_bootinfo_init(void)
+{
+	struct device_node *np;
+	void __iomem *base;
+
+	/* AST2600 only */
+	np = of_find_compatible_node(NULL, NULL, "aspeed,ast2600-sbc");
+	if (!of_device_is_available(np))
+		return -ENODEV;
+
+	base = of_iomap(np, 0);
+	if (!base) {
+		of_node_put(np);
+		return -ENODEV;
+	}
+
+	security_status = readl(base + SEC_STATUS);
+
+	iounmap(base);
+	of_node_put(np);
+
+	firmware_bootinfo_init(aspeed_groups[0]);
+
+	pr_info("AST2600 secure boot %s\n",
+		(security_status & SECURE_BOOT) ? "enabled" : "disabled");
+
+	return 0;
+}
+
 static int __init aspeed_socinfo_init(void)
 {
 	struct soc_device_attribute *attrs;
@@ -148,6 +228,8 @@ static int __init aspeed_socinfo_init(void)
 			attrs->revision,
 			attrs->soc_id);
 
+	aspeed_bootinfo_init();
+
 	return 0;
 }
-early_initcall(aspeed_socinfo_init);
+subsys_initcall(aspeed_socinfo_init);
-- 
2.34.1