[PATCH v4 9/9] powerpc/pseries/vas: Write 'nr_total_credits' for QoS credits change

[Haren Myneni <haren@linux.ibm.com>]

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. With the core add/removal, this value can be changed in HMC
which invokes drmgr to communicate to the kernel.

This patch adds an interface so that drmgr command can write the new
target QoS credits in sysfs. But the kernel gets the new QoS
capabilities from the hypervisor whenever nr_total_credits is updated
to make sure sync with the values in the hypervisor.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
---
 arch/powerpc/platforms/pseries/vas-sysfs.c | 33 +++++++++++++++++++++-
 arch/powerpc/platforms/pseries/vas.c       |  2 +-
 arch/powerpc/platforms/pseries/vas.h       |  1 +
 3 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/vas-sysfs.c b/arch/powerpc/platforms/pseries/vas-sysfs.c
index e24d3edb3021..20745cd75f27 100644
--- a/arch/powerpc/platforms/pseries/vas-sysfs.c
+++ b/arch/powerpc/platforms/pseries/vas-sysfs.c
@@ -25,6 +25,33 @@ 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 nr_total_credits_store(struct vas_cop_feat_caps *caps,
+				       const char *buf, size_t count)
+{
+	int err;
+	u16 creds;
+
+	/*
+	 * Nothing to do for default credit type.
+	 */
+	if (caps->win_type == VAS_GZIP_DEF_FEAT_TYPE)
+		return -EOPNOTSUPP;
+
+	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) 	\
 {									\
@@ -41,6 +68,10 @@ struct vas_sysfs_entry {
 	sysfs_caps_entry_read(_name);		\
 	static struct vas_sysfs_entry _name##_attribute = __ATTR(_name,	\
 				0444, _name##_show, NULL);
+#define VAS_ATTR(_name)							\
+	sysfs_caps_entry_read(_name);					\
+	static struct vas_sysfs_entry _name##_attribute = __ATTR(_name, \
+				0644, _name##_show, _name##_store)
 
 /*
  * Create sysfs interface:
@@ -65,7 +96,7 @@ struct vas_sysfs_entry {
  *	Number of credits used by the user space.
  */
 
-VAS_ATTR_RO(nr_total_credits);
+VAS_ATTR(nr_total_credits);
 VAS_ATTR_RO(nr_used_credits);
 
 static struct attribute *vas_capab_attrs[] = {
diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
index ca0ad191229d..591c7597db5a 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/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;
diff --git a/arch/powerpc/platforms/pseries/vas.h b/arch/powerpc/platforms/pseries/vas.h
index f1bdb776021e..4ddb1001a0aa 100644
--- a/arch/powerpc/platforms/pseries/vas.h
+++ b/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 */
-- 
2.27.0