[PATCH v3] powerpc/powernv: add hdat attribute to sysfs

[Matt Brown]

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 at gmail.com>
---

Changes between v2 to v3:
	- fixed header comments
	- simplified if statement

---
 arch/powerpc/include/asm/opal.h            |  1 +
 arch/powerpc/platforms/powernv/Makefile    |  1 +
 arch/powerpc/platforms/powernv/opal-hdat.c | 65 ++++++++++++++++++++++++++++++
 arch/powerpc/platforms/powernv/opal.c      |  2 +
 4 files changed, 69 insertions(+)
 create mode 100644 arch/powerpc/platforms/powernv/opal-hdat.c

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/Makefile b/arch/powerpc/platforms/powernv/Makefile
index b5d98cb..9a0c9d6 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -3,6 +3,7 @@ obj-y			+= opal-rtc.o opal-nvram.o opal-lpc.o opal-flash.o
 obj-y			+= rng.o opal-elog.o opal-dump.o opal-sysparam.o opal-sensor.o
 obj-y			+= opal-msglog.o opal-hmi.o opal-power.o opal-irqchip.o
 obj-y			+= opal-kmsg.o
+obj-y			+= opal-hdat.o
 
 obj-$(CONFIG_SMP)	+= smp.o subcore.o subcore-asm.o
 obj-$(CONFIG_PCI)	+= pci.o pci-ioda.o npu-dma.o
diff --git a/arch/powerpc/platforms/powernv/opal-hdat.c b/arch/powerpc/platforms/powernv/opal-hdat.c
new file mode 100644
index 0000000..3315dd3
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/opal-hdat.c
@@ -0,0 +1,65 @@
+/*
+ * PowerNV OPAL HDAT interface
+ *
+ * Author: Matt Brown <matthew.brown.dev at gmail.com>
+ *
+ * Copyright 2017 IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/io.h>
+#include <asm/opal.h>
+#include <linux/of.h>
+#include <linux/types.h>
+
+struct hdat_info {
+	char *base;
+	u64 size;
+};
+
+static struct hdat_info hdat_inf;
+
+/* 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 hdat_addr[2];
+
+	/* Check for the hdat-map prop in device-tree */
+	if (of_property_read_u64_array(opal_node, "hdat-map", hdat_addr, 2)) {
+		pr_debug("OPAL: Property hdat-map not found.\n");
+		return;
+	}
+
+	/* Print out hdat-map values. [0]: base, [1]: size */
+	pr_debug("OPAL: HDAT Base address: %#llx\n", hdat_addr[0]);
+	pr_debug("OPAL: HDAT Size: %#llx\n", hdat_addr[1]);
+
+	hdat_inf.base = phys_to_virt(hdat_addr[0]);
+	hdat_inf.size = hdat_addr[1];
+
+	if (sysfs_create_bin_file(opal_kobj, &hdat_attr))
+		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