[PATCH 2/6] drm/i915: rework mmio debug suspend/resume

[Daniele Ceraolo Spurio]

Since we now have a separate object, it is cleaner to have dedicated
functions working on the object to stop and restart the mmio debug.
Apart from the cosmetic changes, this patch introduces 2 functional
updates:

- All calls to check_for_unclaimed_mmio will now return false when
  the debug is suspended, not just the ones that are active only when
  i915_modparams.mmio_debug is set. If we don't trust the result of the
  check while a user is doing mmio access then we shouldn't attempt the
  check anywhere.

- i915_modparams.mmio_debug is not save/restored anymore around user
  access. The value is now never touched by the kernel while debug is
  disabled so no need for save/restore.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c |  2 +-
 drivers/gpu/drm/i915/i915_drv.c     |  2 +-
 drivers/gpu/drm/i915/intel_uncore.c | 43 ++++++++++++++++++-----------
 drivers/gpu/drm/i915/intel_uncore.h |  9 ++----
 4 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index eeecdad0e3ca..1eb72bd74ab9 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1218,7 +1218,7 @@ static int i915_forcewake_domains(struct seq_file *m, void *data)
 	unsigned int tmp;
 
 	seq_printf(m, "user.bypass_count = %u\n",
-		   uncore->user_forcewake.count);
+		   uncore->user_forcewake_count);
 
 	for_each_fw_domain(fw_domain, uncore, tmp)
 		seq_printf(m, "%s.wake_count = %u\n",
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 1c4cfdb04867..2d6c643dde51 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -2204,7 +2204,7 @@ static int i915_drm_suspend_late(struct drm_device *dev, bool hibernation)
 
 out:
 	enable_rpm_wakeref_asserts(rpm);
-	if (!dev_priv->uncore.user_forcewake.count)
+	if (!dev_priv->uncore.user_forcewake_count)
 		intel_runtime_pm_cleanup(rpm);
 
 	return ret;
diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index ec57fd0f3eb5..e0de0b7f264e 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -41,6 +41,25 @@ intel_uncore_mmio_debug_init_early(struct intel_uncore_mmio_debug *mmio_debug)
 	mmio_debug->unclaimed_mmio_check = 1;
 }
 
+void uncore_mmio_debug_suspend(struct intel_uncore_mmio_debug *mmio_debug)
+{
+	lockdep_assert_held(&mmio_debug->lock);
+
+	/* Save and disable mmio debugging for the user bypass */
+	if (!mmio_debug->suspend_count++) {
+		mmio_debug->saved_mmio_check = mmio_debug->unclaimed_mmio_check;
+		mmio_debug->unclaimed_mmio_check = 0;
+	}
+}
+
+void uncore_mmio_debug_resume(struct intel_uncore_mmio_debug *mmio_debug)
+{
+	lockdep_assert_held(&mmio_debug->lock);
+
+	if (!--mmio_debug->suspend_count)
+		mmio_debug->unclaimed_mmio_check = mmio_debug->saved_mmio_check;
+}
+
 static const char * const forcewake_domain_names[] = {
 	"render",
 	"blitter",
@@ -482,6 +501,9 @@ check_for_unclaimed_mmio(struct intel_uncore *uncore)
 
 	lockdep_assert_held(&uncore->debug->lock);
 
+	if (uncore->debug->suspend_count)
+		return false;
+
 	if (intel_uncore_has_fpga_dbg_unclaimed(uncore))
 		ret |= fpga_check_for_unclaimed_mmio(uncore);
 
@@ -615,17 +637,9 @@ void intel_uncore_forcewake_user_get(struct intel_uncore *uncore)
 {
 	spin_lock_irq(&uncore->lock);
 	spin_lock(&uncore->debug->lock);
-	if (!uncore->user_forcewake.count++) {
+	if (!uncore->user_forcewake_count++) {
 		intel_uncore_forcewake_get__locked(uncore, FORCEWAKE_ALL);
-
-		/* Save and disable mmio debugging for the user bypass */
-		uncore->user_forcewake.saved_mmio_check =
-			uncore->debug->unclaimed_mmio_check;
-		uncore->user_forcewake.saved_mmio_debug =
-			i915_modparams.mmio_debug;
-
-		uncore->debug->unclaimed_mmio_check = 0;
-		i915_modparams.mmio_debug = 0;
+		uncore_mmio_debug_suspend(uncore->debug);
 	}
 	spin_unlock(&uncore->debug->lock);
 	spin_unlock_irq(&uncore->lock);
@@ -642,16 +656,13 @@ void intel_uncore_forcewake_user_put(struct intel_uncore *uncore)
 {
 	spin_lock_irq(&uncore->lock);
 	spin_lock(&uncore->debug->lock);
-	if (!--uncore->user_forcewake.count) {
+	if (!--uncore->user_forcewake_count) {
+		uncore_mmio_debug_resume(uncore->debug);
+
 		if (check_for_unclaimed_mmio(uncore))
 			dev_info(uncore->i915->drm.dev,
 				 "Invalid mmio detected during user access\n");
 
-		uncore->debug->unclaimed_mmio_check =
-			uncore->user_forcewake.saved_mmio_check;
-		i915_modparams.mmio_debug =
-			uncore->user_forcewake.saved_mmio_debug;
-
 		intel_uncore_forcewake_put__locked(uncore, FORCEWAKE_ALL);
 	}
 	spin_unlock(&uncore->debug->lock);
diff --git a/drivers/gpu/drm/i915/intel_uncore.h b/drivers/gpu/drm/i915/intel_uncore.h
index d1b12b3b8353..3969dd12208b 100644
--- a/drivers/gpu/drm/i915/intel_uncore.h
+++ b/drivers/gpu/drm/i915/intel_uncore.h
@@ -39,6 +39,8 @@ struct intel_uncore;
 struct intel_uncore_mmio_debug {
 	spinlock_t lock; /** lock is also taken in irq contexts. */
 	int unclaimed_mmio_check;
+	int saved_mmio_check;
+	u32 suspend_count;
 };
 
 enum forcewake_domain_id {
@@ -141,12 +143,7 @@ struct intel_uncore {
 		u32 __iomem *reg_ack;
 	} *fw_domain[FW_DOMAIN_ID_COUNT];
 
-	struct {
-		unsigned int count;
-
-		int saved_mmio_check;
-		int saved_mmio_debug;
-	} user_forcewake;
+	unsigned int user_forcewake_count;
 
 	struct intel_uncore_mmio_debug *debug;
 };
-- 
2.20.1