drm/xe: Add locks in gtidle code

The update of the residency values needs to be protected by a lock to
avoid multiple entrypoints, for example when multiple userspace clients
read the sysfs file. Other in-kernel clients are going to be added to
sample these values, making the problem worse. Protect those updates
with a raw_spinlock so it can be called by future integration with perf
pmu.

Suggested-by: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250110173308.2412232-2-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

diff --git a/drivers/gpu/drm/xe/xe_gt_idle.c b/drivers/gpu/drm/xe/xe_gt_idle.c
index ffd3ba7f6656160eb02d0b3d98ffc639813ec606..fbbace7b0b12a9a7cafe9f991bdd524f2852379b 100644 (file)
--- a/drivers/gpu/drm/xe/xe_gt_idle.c
+++ b/drivers/gpu/drm/xe/xe_gt_idle.c
@@ -69,6 +69,8 @@ static u64 get_residency_ms(struct xe_gt_idle *gtidle, u64 cur_residency)
 {
        u64 delta, overflow_residency, prev_residency;
 
+       lockdep_assert_held(&gtidle->lock);
+
        overflow_residency = BIT_ULL(32);
 
        /*
@@ -275,8 +277,21 @@ static ssize_t idle_status_show(struct device *dev,
 
        return sysfs_emit(buff, "%s\n", gt_idle_state_to_string(state));
 }
-static DEVICE_ATTR_RO(idle_status);
 
+u64 xe_gt_idle_residency_msec(struct xe_gt_idle *gtidle)
+{
+       struct xe_guc_pc *pc = gtidle_to_pc(gtidle);
+       u64 residency;
+       unsigned long flags;
+
+       raw_spin_lock_irqsave(&gtidle->lock, flags);
+       residency = get_residency_ms(gtidle, gtidle->idle_residency(pc));
+       raw_spin_unlock_irqrestore(&gtidle->lock, flags);
+
+       return residency;
+}
+
+static DEVICE_ATTR_RO(idle_status);
 static ssize_t idle_residency_ms_show(struct device *dev,
                                      struct device_attribute *attr, char *buff)
 {
@@ -285,10 +300,10 @@ static ssize_t idle_residency_ms_show(struct device *dev,
        u64 residency;
 
        xe_pm_runtime_get(pc_to_xe(pc));
-       residency = gtidle->idle_residency(pc);
+       residency = xe_gt_idle_residency_msec(gtidle);
        xe_pm_runtime_put(pc_to_xe(pc));
 
-       return sysfs_emit(buff, "%llu\n", get_residency_ms(gtidle, residency));
+       return sysfs_emit(buff, "%llu\n", residency);
 }
 static DEVICE_ATTR_RO(idle_residency_ms);
 
@@ -331,6 +346,8 @@ int xe_gt_idle_init(struct xe_gt_idle *gtidle)
        if (!kobj)
                return -ENOMEM;
 
+       raw_spin_lock_init(&gtidle->lock);
+
        if (xe_gt_is_media_type(gt)) {
                snprintf(gtidle->name, sizeof(gtidle->name), "gt%d-mc", gt->info.id);
                gtidle->idle_residency = xe_guc_pc_mc6_residency;

diff --git a/drivers/gpu/drm/xe/xe_gt_idle.h b/drivers/gpu/drm/xe/xe_gt_idle.h
index 4455a6501cb0735cde1a2cfa9da5f0e6a5dff6eb..591a01e181bcc27b8bf6729efea2c46276abcc2b 100644 (file)
--- a/drivers/gpu/drm/xe/xe_gt_idle.h
+++ b/drivers/gpu/drm/xe/xe_gt_idle.h
@@ -17,5 +17,6 @@ void xe_gt_idle_disable_c6(struct xe_gt *gt);
 void xe_gt_idle_enable_pg(struct xe_gt *gt);
 void xe_gt_idle_disable_pg(struct xe_gt *gt);
 int xe_gt_idle_pg_print(struct xe_gt *gt, struct drm_printer *p);
+u64 xe_gt_idle_residency_msec(struct xe_gt_idle *gtidle);
 
 #endif /* _XE_GT_IDLE_H_ */

diff --git a/drivers/gpu/drm/xe/xe_gt_idle_types.h b/drivers/gpu/drm/xe/xe_gt_idle_types.h
index b8b297a3f8848e65c4b2314389eb5688413cc4e2..a3667c567f8a7d93abad054e818fe8424621b4ae 100644 (file)
--- a/drivers/gpu/drm/xe/xe_gt_idle_types.h
+++ b/drivers/gpu/drm/xe/xe_gt_idle_types.h
@@ -6,6 +6,7 @@
 #ifndef _XE_GT_IDLE_SYSFS_TYPES_H_
 #define _XE_GT_IDLE_SYSFS_TYPES_H_
 
+#include <linux/spinlock.h>
 #include <linux/types.h>
 
 struct xe_guc_pc;
@@ -31,6 +32,8 @@ struct xe_gt_idle {
        u64 cur_residency;
        /** @prev_residency: previous residency counter */
        u64 prev_residency;
+       /** @lock: Lock protecting idle residency counters */
+       raw_spinlock_t lock;
        /** @idle_status: get the current idle state */
        enum xe_gt_idle_state (*idle_status)(struct xe_guc_pc *pc);
        /** @idle_residency: get idle residency counter */