[PATCH v6 7/7] soc/tegra: Expose Boot Configuration Table via sysfs

[Dmitry Osipenko <digetx@gmail.com>]

It's quite useful to have unencrypted BCT exposed to userspace for
debugging purposes, so let's expose it via sysfs.  The BCT data will be
present in '/sys/tegra/boot_config_table' binary file if BCT is available.

Suggested-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 arch/arm/mach-tegra/tegra.c  |  4 +++
 drivers/soc/tegra/Makefile   |  1 +
 drivers/soc/tegra/bootdata.c | 51 ++++++++++++++++++++++++++++++++++++
 drivers/soc/tegra/common.c   | 17 ++++++++++++
 include/soc/tegra/bootdata.h |  2 ++
 include/soc/tegra/common.h   |  3 +++
 6 files changed, 78 insertions(+)
 create mode 100644 drivers/soc/tegra/bootdata.c

diff --git a/arch/arm/mach-tegra/tegra.c b/arch/arm/mach-tegra/tegra.c
index da6bcd85398b..5f40463f1b97 100644
--- a/arch/arm/mach-tegra/tegra.c
+++ b/arch/arm/mach-tegra/tegra.c
@@ -72,6 +72,7 @@ static void __init tegra_boot_config_table_init(void)
 	u32 iram_end   = TEGRA_IRAM_BASE + TEGRA_IRAM_SIZE;
 	u32 iram_start = TEGRA_IRAM_BASE;
 	u32 pt_addr, pt_size, bct_size;
+	void __iomem *bct_ptr;
 
 	t20_bit = IO_ADDRESS(TEGRA_IRAM_BASE);
 
@@ -90,6 +91,7 @@ static void __init tegra_boot_config_table_init(void)
 
 		pt_addr = t20_bct->partition_table_logical_sector_address;
 		pt_size = t20_bct->partition_table_num_logical_sectors;
+		bct_ptr = t20_bct;
 
 	} else if (of_machine_is_compatible("nvidia,tegra30")) {
 		bct_size = sizeof(*t30_bct);
@@ -106,12 +108,14 @@ static void __init tegra_boot_config_table_init(void)
 
 		pt_addr = t30_bct->partition_table_logical_sector_address;
 		pt_size = t30_bct->partition_table_num_logical_sectors;
+		bct_ptr = t30_bct;
 	} else {
 		return;
 	}
 
 	pr_info("%s: BCT found in IRAM\n", __func__);
 
+	tegra_bootdata_bct_setup(bct_ptr, bct_size);
 	tegra_partition_table_setup(pt_addr, pt_size);
 }
 
diff --git a/drivers/soc/tegra/Makefile b/drivers/soc/tegra/Makefile
index 9c809c1814bd..8be2bfb4d95d 100644
--- a/drivers/soc/tegra/Makefile
+++ b/drivers/soc/tegra/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-y += fuse/
 
+obj-y += bootdata.o
 obj-y += common.o
 obj-$(CONFIG_SOC_TEGRA_FLOWCTRL) += flowctrl.o
 obj-$(CONFIG_SOC_TEGRA_PMC) += pmc.o
diff --git a/drivers/soc/tegra/bootdata.c b/drivers/soc/tegra/bootdata.c
new file mode 100644
index 000000000000..3d028e0d343d
--- /dev/null
+++ b/drivers/soc/tegra/bootdata.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include <soc/tegra/bootdata.h>
+#include <soc/tegra/common.h>
+
+/*
+ * spare_bct[] will be released once kernel is booted, hence not wasting
+ * kernel space if BCT is missing. The tegra_bct can't be allocated during
+ * of BCT setting up because it's too early for the slab allocator.
+ */
+static u8 spare_bct[SZ_8K] __initdata;
+static u8 *tegra_bct;
+
+static ssize_t boot_config_table_read(struct file *filp,
+				      struct kobject *kobj,
+				      struct bin_attribute *bin_attr,
+				      char *buf, loff_t off, size_t count)
+{
+	memcpy(buf, tegra_bct + off, count);
+	return count;
+}
+static BIN_ATTR_RO(boot_config_table, 0);
+
+static int __init tegra_bootdata_bct_sysfs_init(void)
+{
+	if (!bin_attr_boot_config_table.size)
+		return 0;
+
+	tegra_bct = kmalloc(bin_attr_boot_config_table.size, GFP_KERNEL);
+	if (!tegra_bct)
+		return -ENOMEM;
+
+	memcpy(tegra_bct, spare_bct, bin_attr_boot_config_table.size);
+
+	return sysfs_create_bin_file(tegra_soc_kobj,
+				     &bin_attr_boot_config_table);
+}
+late_initcall(tegra_bootdata_bct_sysfs_init)
+
+void __init tegra_bootdata_bct_setup(void __iomem *bct_ptr, size_t bct_size)
+{
+	memcpy_fromio(spare_bct, bct_ptr, bct_size);
+	bin_attr_boot_config_table.size = bct_size;
+}
diff --git a/drivers/soc/tegra/common.c b/drivers/soc/tegra/common.c
index 3dc54f59cafe..2b4b49eacb2e 100644
--- a/drivers/soc/tegra/common.c
+++ b/drivers/soc/tegra/common.c
@@ -3,10 +3,15 @@
  * Copyright (C) 2014 NVIDIA CORPORATION.  All rights reserved.
  */
 
+#include <linux/init.h>
+#include <linux/kernel.h>
 #include <linux/of.h>
+#include <linux/sysfs.h>
 
 #include <soc/tegra/common.h>
 
+struct kobject *tegra_soc_kobj;
+
 static const struct of_device_id tegra_machine_match[] = {
 	{ .compatible = "nvidia,tegra20", },
 	{ .compatible = "nvidia,tegra30", },
@@ -31,3 +36,15 @@ bool soc_is_tegra(void)
 
 	return match != NULL;
 }
+
+static int __init tegra_soc_sysfs_init(void)
+{
+	if (!soc_is_tegra())
+		return 0;
+
+	tegra_soc_kobj = kobject_create_and_add("tegra", NULL);
+	WARN_ON(!tegra_soc_kobj);
+
+	return 0;
+}
+arch_initcall(tegra_soc_sysfs_init)
diff --git a/include/soc/tegra/bootdata.h b/include/soc/tegra/bootdata.h
index 7be207cb2519..d5c7a251517d 100644
--- a/include/soc/tegra/bootdata.h
+++ b/include/soc/tegra/bootdata.h
@@ -43,4 +43,6 @@ struct tegra30_boot_config_table {
 	u32 unused_data[3];
 } __packed;
 
+void tegra_bootdata_bct_setup(void __iomem *bct_ptr, size_t bct_size);
+
 #endif /* __SOC_TEGRA_BOOTDATA_H__ */
diff --git a/include/soc/tegra/common.h b/include/soc/tegra/common.h
index 744280ecab5f..0bc11b45c98e 100644
--- a/include/soc/tegra/common.h
+++ b/include/soc/tegra/common.h
@@ -7,8 +7,11 @@
 #define __SOC_TEGRA_COMMON_H__
 
 #include <linux/types.h>
+#include <linux/sysfs.h>
 
 #ifdef CONFIG_ARCH_TEGRA
+extern struct kobject *tegra_soc_kobj;
+
 bool soc_is_tegra(void);
 #else
 static inline bool soc_is_tegra(void)
-- 
2.26.0