powerpc/pseries/vas: Add 'update_total_credits' entry for QoS capabilities

pseries supports two types of credits - Default (uses normal priority
FIFO) and Qality of service (QoS uses high priority FIFO). The user
decides the number of QoS credits and sets this value with HMC
interface. The total credits for QoS capabilities can be changed
dynamically with HMC interface which invokes drmgr to communicate
to the kernel.

This patch creats 'update_total_credits' entry for QoS capabilities
so that drmgr command can write the new target QoS credits in sysfs.
Instead of using this value, the kernel gets the new QoS capabilities
from the hypervisor whenever update_total_credits is updated to make
sure sync with the QoS target credits in the hypervisor.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b01ef31a0f964686d00243e7de7f09c73c07e69e.camel@linux.ibm.com

arch/powerpc/platforms/pseries/vas-sysfs.c

@@ -25,6 +25,27 @@ struct vas_caps_entry {
 
 #define to_caps_entry(entry) container_of(entry, struct vas_caps_entry, kobj)
 
+/*
+ * This function is used to get the notification from the drmgr when
+ * QoS credits are changed. Though receiving the target total QoS
+ * credits here, get the official QoS capabilities from the hypervisor.
+ */
+static ssize_t update_total_credits_trigger(struct vas_cop_feat_caps *caps,
+						const char *buf, size_t count)
+{
+	int err;
+	u16 creds;
+
+	err = kstrtou16(buf, 0, &creds);
+	if (!err)
+		err = vas_reconfig_capabilties(caps->win_type);
+
+	if (err)
+		return -EINVAL;
+
+	return count;
+}
+
 #define sysfs_caps_entry_read(_name)					\
 static ssize_t _name##_show(struct vas_cop_feat_caps *caps, char *buf) 	\
 {									\
@@ -63,17 +84,29 @@ struct vas_sysfs_entry {
  *	changed dynamically by the user.
  * /sys/devices/vas/vas0/gzip/qos_capabilities/nr_used_credits
  *	Number of credits used by the user space.
+ * /sys/devices/vas/vas0/gzip/qos_capabilities/update_total_credits
+ *	Update total QoS credits dynamically
  */
 
 VAS_ATTR_RO(nr_total_credits);
 VAS_ATTR_RO(nr_used_credits);
 
-static struct attribute *vas_capab_attrs[] = {
+static struct vas_sysfs_entry update_total_credits_attribute =
+	__ATTR(update_total_credits, 0200, NULL, update_total_credits_trigger);
+
+static struct attribute *vas_def_capab_attrs[] = {
 	&nr_total_credits_attribute.attr,
 	&nr_used_credits_attribute.attr,
 	NULL,
 };
 
+static struct attribute *vas_qos_capab_attrs[] = {
+	&nr_total_credits_attribute.attr,
+	&nr_used_credits_attribute.attr,
+	&update_total_credits_attribute.attr,
+	NULL,
+};
+
 static ssize_t vas_type_show(struct kobject *kobj, struct attribute *attr,
 			     char *buf)
 {
@@ -118,19 +151,29 @@ static const struct sysfs_ops vas_sysfs_ops = {
 	.store	=	vas_type_store,
 };
 
-static struct kobj_type vas_attr_type = {
+static struct kobj_type vas_def_attr_type = {
 		.release	=	vas_type_release,
 		.sysfs_ops      =       &vas_sysfs_ops,
-		.default_attrs  =       vas_capab_attrs,
+		.default_attrs  =       vas_def_capab_attrs,
 };
 
-static char *vas_caps_kobj_name(struct vas_cop_feat_caps *caps,
+static struct kobj_type vas_qos_attr_type = {
+		.release	=	vas_type_release,
+		.sysfs_ops	=	&vas_sysfs_ops,
+		.default_attrs	=	vas_qos_capab_attrs,
+};
+
+static char *vas_caps_kobj_name(struct vas_caps_entry *centry,
 				struct kobject **kobj)
 {
+	struct vas_cop_feat_caps *caps = centry->caps;
+
 	if (caps->descriptor == VAS_GZIP_QOS_CAPABILITIES) {
+		kobject_init(&centry->kobj, &vas_qos_attr_type);
 		*kobj = gzip_caps_kobj;
 		return "qos_capabilities";
 	} else if (caps->descriptor == VAS_GZIP_DEFAULT_CAPABILITIES) {
+		kobject_init(&centry->kobj, &vas_def_attr_type);
 		*kobj = gzip_caps_kobj;
 		return "default_capabilities";
 	} else
@@ -152,9 +195,8 @@ int sysfs_add_vas_caps(struct vas_cop_feat_caps *caps)
 	if (!centry)
 		return -ENOMEM;
 
-	kobject_init(&centry->kobj, &vas_attr_type);
 	centry->caps = caps;
-	name  = vas_caps_kobj_name(caps, &kobj);
+	name  = vas_caps_kobj_name(centry, &kobj);
 
 	if (kobj) {
 		ret = kobject_add(&centry->kobj, kobj, "%s", name);

arch/powerpc/platforms/pseries/vas.c

@@ -722,7 +722,7 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds)
  * changes. Reconfig window configurations based on the credits
  * availability from this new capabilities.
  */
-static int vas_reconfig_capabilties(u8 type)
+int vas_reconfig_capabilties(u8 type)
 {
 	struct hv_vas_cop_feat_caps *hv_caps;
 	struct vas_cop_feat_caps *caps;

arch/powerpc/platforms/pseries/vas.h

@@ -130,5 +130,6 @@ struct pseries_vas_window {
 };
 
 int sysfs_add_vas_caps(struct vas_cop_feat_caps *caps);
+int vas_reconfig_capabilties(u8 type);
 int __init sysfs_pseries_vas_init(struct vas_all_caps *vas_caps);
 #endif /* _VAS_H */