[PATCH] powerpc/powernv: add hdat attribute to sysfs

[Matt Brown <matthew.brown.dev@gmail.com>]

From: Matt Brown <brownmatt1997@gmail.com>

The HDAT data area is consumed by skiboot and turned into a device-tree.
In some cases we would like to look directly at the HDAT, so this patch
adds a sysfs node to allow it to be viewed.  This is not possible through
/dev/mem as it is reserved memory which is stopped by the /dev/mem filter.

Signed-off-by: Matt Brown <matthew.brown.dev@gmail.com>
---
 arch/powerpc/include/asm/opal.h              |  1 +
 arch/powerpc/platforms/powernv/opal-msglog.c | 49 ++++++++++++++++++++++++++++
 arch/powerpc/platforms/powernv/opal.c        |  2 ++
 3 files changed, 52 insertions(+)

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 5c7db0f..b26944e 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -277,6 +277,7 @@ extern int opal_async_comp_init(void);
 extern int opal_sensor_init(void);
 extern int opal_hmi_handler_init(void);
 extern int opal_event_init(void);
+extern void opal_hdat_sysfs_init(void);
 
 extern int opal_machine_check(struct pt_regs *regs);
 extern bool opal_mce_check_early_recovery(struct pt_regs *regs);
diff --git a/arch/powerpc/platforms/powernv/opal-msglog.c b/arch/powerpc/platforms/powernv/opal-msglog.c
index 39d6ff9..a637055 100644
--- a/arch/powerpc/platforms/powernv/opal-msglog.c
+++ b/arch/powerpc/platforms/powernv/opal-msglog.c
@@ -31,7 +31,13 @@ struct memcons {
 	__be32 in_cons;
 };
 
+struct hdatInfo {
+	char *base;
+	u64 size;
+};
+
 static struct memcons *opal_memcons = NULL;
+static struct hdatInfo hdat_inf;
 
 ssize_t opal_msglog_copy(char *to, loff_t pos, size_t count)
 {
@@ -136,3 +142,46 @@ void __init opal_msglog_sysfs_init(void)
 	if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
 		pr_warn("OPAL: sysfs file creation failed\n");
 }
+
+
+
+/* Read function for HDAT attribute in sysfs */
+static ssize_t hdat_read(struct file *file, struct kobject *kobj,
+			 struct bin_attribute *bin_attr, char *to,
+			 loff_t pos, size_t count)
+{
+	if (!hdat_inf.base)
+		return -ENODEV;
+
+	return memory_read_from_buffer(to, count, &pos, hdat_inf.base,
+					hdat_inf.size);
+}
+
+
+/* HDAT attribute for sysfs */
+static struct bin_attribute hdat_attr = {
+	.attr = {.name = "hdat", .mode = 0444},
+	.read = hdat_read
+};
+
+void __init opal_hdat_sysfs_init(void)
+{
+	u64 hdatAddr[2];
+
+	/* Check for the hdat-map prop in device-tree */
+	if (of_property_read_u64_array(opal_node, "hdat-map", hdatAddr, 2)) {
+		pr_debug("OPAL: Property hdat-map not found.\n");
+		return;
+	}
+
+	/* Print out hdat-map values. [0]: base, [1]: size */
+	pr_debug("HDAT Base address: %#llx\n", hdatAddr[0]);
+	pr_debug("HDAT Size: %#llx\n", hdatAddr[1]);
+
+	hdat_inf.base = phys_to_virt(hdatAddr[0]);
+	hdat_inf.size = hdatAddr[1];
+
+	if (sysfs_create_bin_file(opal_kobj, &hdat_attr) != 0)
+		pr_debug("OPAL: sysfs file creation for HDAT failed");
+
+}
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 2822935..cae3745 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -740,6 +740,8 @@ static int __init opal_init(void)
 		opal_sys_param_init();
 		/* Setup message log sysfs interface. */
 		opal_msglog_sysfs_init();
+		/* Create hdat object under sys/firmware/opal */
+		opal_hdat_sysfs_init();
 	}
 
 	/* Initialize platform devices: IPMI backend, PRD & flash interface */
-- 
2.9.3