[PATCH v2] powernv: powercap: Add hard minimum powercap

[Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>]

In POWER9, OCC(On-Chip-Controller) provides for hard and soft system
powercapping range. The hard powercap range is guaranteed while soft
powercap may or may not be enforced by OCC due to various power-thermal
reasons based on system configuration and workloads. This patch adds
a sysfs file to export the hard minimum powercap limit to allow the
user to set the appropriate powercap value that can be managed by the
system.

Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
---
Changes from V1:
- s/asserted/enforced by OCC

 .../ABI/testing/sysfs-firmware-opal-powercap       | 10 ++++
 arch/powerpc/platforms/powernv/opal-powercap.c     | 66 +++++++++-------------
 2 files changed, 37 insertions(+), 39 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-firmware-opal-powercap b/Documentation/ABI/testing/sysfs-firmware-opal-powercap
index c9b66ec..e37d43e 100644
--- a/Documentation/ABI/testing/sysfs-firmware-opal-powercap
+++ b/Documentation/ABI/testing/sysfs-firmware-opal-powercap
@@ -29,3 +29,13 @@ Description:	System powercap directory and attributes applicable for
 		  creates a request for setting a new-powercap. The
 		  powercap requested must be between powercap-min
 		  and powercap-max.
+
+What:		/sys/firmware/opal/powercap/system-powercap/powercap-hard-min
+Date:		March 2019
+Contact:	Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
+Description:	Hard minimum powercap
+
+		This file provides the hard minimum powercap limit in Watts.
+		The powercap value above hard minimum limit is guaranteed to be
+		enforced by OCC and the powercap value below this limit may or
+		may not be guaranteed.
diff --git a/arch/powerpc/platforms/powernv/opal-powercap.c b/arch/powerpc/platforms/powernv/opal-powercap.c
index d90ee4f..38408e7 100644
--- a/arch/powerpc/platforms/powernv/opal-powercap.c
+++ b/arch/powerpc/platforms/powernv/opal-powercap.c
@@ -139,10 +139,24 @@ static void powercap_add_attr(int handle, const char *name,
 	attr->handle = handle;
 	sysfs_attr_init(&attr->attr.attr);
 	attr->attr.attr.name = name;
-	attr->attr.attr.mode = 0444;
+
+	if (!strncmp(name, "powercap-current", strlen(name))) {
+		attr->attr.attr.mode = 0664;
+		attr->attr.store = powercap_store;
+	} else {
+		attr->attr.attr.mode = 0444;
+	}
+
 	attr->attr.show = powercap_show;
 }
 
+static const char * const powercap_strs[] = {
+	"powercap-max",
+	"powercap-min",
+	"powercap-current",
+	"powercap-hard-min",
+};
+
 void __init opal_powercap_init(void)
 {
 	struct device_node *powercap, *node;
@@ -167,60 +181,34 @@ void __init opal_powercap_init(void)
 
 	i = 0;
 	for_each_child_of_node(powercap, node) {
-		u32 cur, min, max;
-		int j = 0;
-		bool has_cur = false, has_min = false, has_max = false;
+		u32 id;
+		int j, count = 0;
 
-		if (!of_property_read_u32(node, "powercap-min", &min)) {
-			j++;
-			has_min = true;
-		}
-
-		if (!of_property_read_u32(node, "powercap-max", &max)) {
-			j++;
-			has_max = true;
-		}
+		for (j = 0; j < ARRAY_SIZE(powercap_strs); j++)
+			if (!of_property_read_u32(node, powercap_strs[j], &id))
+				count++;
 
-		if (!of_property_read_u32(node, "powercap-current", &cur)) {
-			j++;
-			has_cur = true;
-		}
-
-		pcaps[i].pattrs = kcalloc(j, sizeof(struct powercap_attr),
+		pcaps[i].pattrs = kcalloc(count, sizeof(struct powercap_attr),
 					  GFP_KERNEL);
 		if (!pcaps[i].pattrs)
 			goto out_pcaps_pattrs;
 
-		pcaps[i].pg.attrs = kcalloc(j + 1, sizeof(struct attribute *),
+		pcaps[i].pg.attrs = kcalloc(count + 1,
+					    sizeof(struct attribute *),
 					    GFP_KERNEL);
 		if (!pcaps[i].pg.attrs) {
 			kfree(pcaps[i].pattrs);
 			goto out_pcaps_pattrs;
 		}
 
-		j = 0;
 		pcaps[i].pg.name = kasprintf(GFP_KERNEL, "%pOFn", node);
-		if (has_min) {
-			powercap_add_attr(min, "powercap-min",
-					  &pcaps[i].pattrs[j]);
-			pcaps[i].pg.attrs[j] = &pcaps[i].pattrs[j].attr.attr;
-			j++;
-		}
-
-		if (has_max) {
-			powercap_add_attr(max, "powercap-max",
-					  &pcaps[i].pattrs[j]);
-			pcaps[i].pg.attrs[j] = &pcaps[i].pattrs[j].attr.attr;
-			j++;
-		}
+		for (j = 0; j < ARRAY_SIZE(powercap_strs); j++) {
+			if (of_property_read_u32(node, powercap_strs[j], &id))
+				continue;
 
-		if (has_cur) {
-			powercap_add_attr(cur, "powercap-current",
+			powercap_add_attr(id, powercap_strs[j],
 					  &pcaps[i].pattrs[j]);
-			pcaps[i].pattrs[j].attr.attr.mode |= 0220;
-			pcaps[i].pattrs[j].attr.store = powercap_store;
 			pcaps[i].pg.attrs[j] = &pcaps[i].pattrs[j].attr.attr;
-			j++;
 		}
 
 		if (sysfs_create_group(powercap_kobj, &pcaps[i].pg)) {
-- 
1.8.3.1