drm/i915/hwmon: Block waiting for GuC reset to complete

Instead of erroring out when GuC reset is in progress, block waiting for
GuC reset to complete which is a more reasonable uapi behavior.

v2: Avoid race between wake_up_all and waiting for wakeup (Rodrigo)
v3: Remove timeout when blocked (Tvrtko)

Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230420164041.1428455-4-ashutosh.dixit@intel.com

diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
index 9ab8971679fe3f13459be91d0c1c91dbb9444fbc..a3bdd9f68a458287c70de6d048d0527da3eae177 100644 (file)
--- a/drivers/gpu/drm/i915/i915_hwmon.c
+++ b/drivers/gpu/drm/i915/i915_hwmon.c
@@ -51,6 +51,7 @@ struct hwm_drvdata {
        char name[12];
        int gt_n;
        bool reset_in_progress;
+       wait_queue_head_t waitq;
 };
 
 struct i915_hwmon {
@@ -397,14 +398,32 @@ hwm_power_max_write(struct hwm_drvdata *ddat, long val)
 {
        struct i915_hwmon *hwmon = ddat->hwmon;
        intel_wakeref_t wakeref;
+       DEFINE_WAIT(wait);
        int ret = 0;
        u32 nval;
 
-       mutex_lock(&hwmon->hwmon_lock);
-       if (hwmon->ddat.reset_in_progress) {
-               ret = -EAGAIN;
-               goto unlock;
+       /* Block waiting for GuC reset to complete when needed */
+       for (;;) {
+               mutex_lock(&hwmon->hwmon_lock);
+
+               prepare_to_wait(&ddat->waitq, &wait, TASK_INTERRUPTIBLE);
+
+               if (!hwmon->ddat.reset_in_progress)
+                       break;
+
+               if (signal_pending(current)) {
+                       ret = -EINTR;
+                       break;
+               }
+
+               mutex_unlock(&hwmon->hwmon_lock);
+
+               schedule();
        }
+       finish_wait(&ddat->waitq, &wait);
+       if (ret)
+               goto unlock;
+
        wakeref = intel_runtime_pm_get(ddat->uncore->rpm);
 
        /* Disable PL1 limit and verify, because the limit cannot be disabled on all platforms */
@@ -508,6 +527,7 @@ void i915_hwmon_power_max_restore(struct drm_i915_private *i915, bool old)
        intel_uncore_rmw(hwmon->ddat.uncore, hwmon->rg.pkg_rapl_limit,
                         PKG_PWR_LIM_1_EN, old ? PKG_PWR_LIM_1_EN : 0);
        hwmon->ddat.reset_in_progress = false;
+       wake_up_all(&hwmon->ddat.waitq);
 
        mutex_unlock(&hwmon->hwmon_lock);
 }
@@ -784,6 +804,7 @@ void i915_hwmon_register(struct drm_i915_private *i915)
        ddat->uncore = &i915->uncore;
        snprintf(ddat->name, sizeof(ddat->name), "i915");
        ddat->gt_n = -1;
+       init_waitqueue_head(&ddat->waitq);
 
        for_each_gt(gt, i915, i) {
                ddat_gt = hwmon->ddat_gt + i;