Hi,
On 17-08-17 14:22, Imre Deak wrote:
On Mon, Aug 14, 2017 at 09:58:32PM +0200, Hans de Goede wrote:
intel_uncore_forcewake_reset() does forcewake puts and gets as such
we need to make sure that no-one tries to access the PUNIT->PMIC bus
(on systems where this bus is shared) while it runs, otherwise bad
things happen.
Normally this is taken care of by the i915_pmic_bus_access_notifier()
which does an intel_uncore_forcewake_get(FORCEWAKE_ALL) when some other
driver tries to access the PMIC bus, so that later forcewake gets are
no-ops (for the duration of the bus access).
But intel_uncore_forcewake_reset gets called in 3 cases:
1) Before registering the pmic_bus_access_notifier
2) After unregistering the pmic_bus_access_notifier
3) To reset forcewake state on a GPU reset
In all 3 cases the i915_pmic_bus_access_notifier() protection is
insufficient.
This commit fixes this race by calling iosf_mbi_punit_acquire() before
calling intel_uncore_forcewake_reset(). In the case where it is called
directly after unregistering the pmic_bus_access_notifier, we need to
hold the punit-lock over both calls to avoid a race where
intel_uncore_fw_release_timer() may execute between the 2 calls.
To allow holding the lock over both calls we need an unlocked
variant of iosf_mbi_unregister_pmic_bus_access_notifier. Since
intel_uncore.c is the only user of this function, we simply
modify it in this commit. Doing this in a separate commit would
require first adding an unlocked variant, then this commit and
then removing the unused normal variant.
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
Changes in v2:
-Rebase on current (July 6th 2017) drm-next
Changes in v3:
-Keep punit acquired / locked over the unregister + forcewake_reset
call combo to avoid a race hitting between the 2 calls
-This requires modifying iosf_mbi_unregister_pmic_bus_access_notifier
to not take the lock itself, since we are the only users this is done
in this same commit
---
arch/x86/include/asm/iosf_mbi.h | 10 ++++++++--
arch/x86/platform/intel/iosf_mbi.c | 14 +++++---------
drivers/gpu/drm/i915/intel_uncore.c | 17 +++++++++++++----
3 files changed, 26 insertions(+), 15 deletions(-)
diff --git a/arch/x86/include/asm/iosf_mbi.h b/arch/x86/include/asm/iosf_mbi.h
index c313cac36f56..f8841bb06d98 100644
--- a/arch/x86/include/asm/iosf_mbi.h
+++ b/arch/x86/include/asm/iosf_mbi.h
@@ -141,9 +141,14 @@ int iosf_mbi_register_pmic_bus_access_notifier(struct notifier_block *nb);
/**
* iosf_mbi_register_pmic_bus_access_notifier - Unregister PMIC bus notifier
You missed the rename in the doc.
Thx, fixed for v4.
*
+ * Note the caller must call iosf_mbi_punit_acquire() before calling this
+ * to ensure the bus is inactive before unregistering (and call
+ * iosf_mbi_punit_release() afterwards).
+ *
* @nb: notifier_block to unregister
*/
-int iosf_mbi_unregister_pmic_bus_access_notifier(struct notifier_block *nb);
+int iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
+ struct notifier_block *nb);
/**
* iosf_mbi_call_pmic_bus_access_notifier_chain - Call PMIC bus notifier chain
@@ -191,7 +196,8 @@ int iosf_mbi_register_pmic_bus_access_notifier(struct notifier_block *nb)
}
static inline
-int iosf_mbi_unregister_pmic_bus_access_notifier(struct notifier_block *nb)
+int iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
+ struct notifier_block *nb)
{
return 0;
}
diff --git a/arch/x86/platform/intel/iosf_mbi.c b/arch/x86/platform/intel/iosf_mbi.c
index a952ac199741..5596a3ec1b89 100644
--- a/arch/x86/platform/intel/iosf_mbi.c
+++ b/arch/x86/platform/intel/iosf_mbi.c
@@ -218,19 +218,15 @@ int iosf_mbi_register_pmic_bus_access_notifier(struct notifier_block *nb)
}
EXPORT_SYMBOL(iosf_mbi_register_pmic_bus_access_notifier);
-int iosf_mbi_unregister_pmic_bus_access_notifier(struct notifier_block *nb)
+int iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
+ struct notifier_block *nb)
{
- int ret;
+ WARN_ON(!mutex_is_locked(&iosf_mbi_punit_mutex));
- /* Wait for the bus to go inactive before unregistering */
- mutex_lock(&iosf_mbi_punit_mutex);
- ret = blocking_notifier_chain_unregister(
+ return blocking_notifier_chain_unregister(
&iosf_mbi_pmic_bus_access_notifier, nb);
- mutex_unlock(&iosf_mbi_punit_mutex);
-
- return ret;
}
-EXPORT_SYMBOL(iosf_mbi_unregister_pmic_bus_access_notifier);
+EXPORT_SYMBOL(iosf_mbi_unregister_pmic_bus_access_notifier_unlocked);
int iosf_mbi_call_pmic_bus_access_notifier_chain(unsigned long val, void *v)
{
diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 569d115918eb..7be6150520ed 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -229,6 +229,7 @@ intel_uncore_fw_release_timer(struct hrtimer *timer)
return HRTIMER_NORESTART;
}
+/* Note callers must have acquired the PUNIT->PMIC bus, before calling this. */
Nit: could use an iosf_assert_mbi_punit_mutex_held() helper instead of
the comment. (taking CONFIG_IOSF_MBI into account)
Good idea, done for v4 (as iosf_mbi_assert_punit_acquired).
static void intel_uncore_forcewake_reset(struct drm_i915_private *dev_priv,
bool restore)
{
@@ -416,14 +417,18 @@ static void __intel_uncore_early_sanitize(struct drm_i915_private *dev_priv,
GT_FIFO_CTL_RC6_POLICY_STALL);
}
+ iosf_mbi_punit_acquire();
intel_uncore_forcewake_reset(dev_priv, restore_forcewake);
+ iosf_mbi_punit_release();
}
void intel_uncore_suspend(struct drm_i915_private *dev_priv)
{
- iosf_mbi_unregister_pmic_bus_access_notifier(
+ iosf_mbi_punit_acquire();
+ iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
&dev_priv->uncore.pmic_bus_access_nb);
intel_uncore_forcewake_reset(dev_priv, false);
+ iosf_mbi_punit_release();
}
void intel_uncore_resume_early(struct drm_i915_private *dev_priv)
@@ -1246,12 +1251,14 @@ void intel_uncore_init(struct drm_i915_private *dev_priv)
void intel_uncore_fini(struct drm_i915_private *dev_priv)
{
- iosf_mbi_unregister_pmic_bus_access_notifier(
- &dev_priv->uncore.pmic_bus_access_nb);
-
/* Paranoia: make sure we have disabled everything before we exit. */
intel_uncore_sanitize(dev_priv);
+
+ iosf_mbi_punit_acquire();
+ iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
+ &dev_priv->uncore.pmic_bus_access_nb);
intel_uncore_forcewake_reset(dev_priv, false);
+ iosf_mbi_punit_release();
}
#define GEN_RANGE(l, h) GENMASK((h) - 1, (l) - 1)
@@ -1524,7 +1531,9 @@ static int gen6_reset_engines(struct drm_i915_private *dev_priv,
ret = gen6_hw_domain_reset(dev_priv, hw_mask);
+ iosf_mbi_punit_acquire();
intel_uncore_forcewake_reset(dev_priv, true);
+ iosf_mbi_punit_release();
return ret;
}
There is one more spot in intel_uncore_check_forcewake_domains() calling
intel_uncore_forcewake_reset() you missed.
Ugh, I did not check for intel_uncore_forcewake_reset() usage outside
of intel_uncore.c as it is a static function, the include magic used
for the selftests caught me by suprise there.
With the above fixes and optional change for the nit looks ok:
Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
Thanks, v4 with everything fixed is coming up.
Regards,
Hans
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