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Commit a5266db4 authored by Hans de Goede's avatar Hans de Goede Committed by Hans de Goede
Browse files

drm/i915: Acquire PUNIT->PMIC bus for intel_uncore_forcewake_reset() 



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.

Reviewed-by: default avatarImre Deak <imre.deak@intel.com>
Acked-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171019111620.26761-3-hdegoede@redhat.com
parent af0ab55f

drivers/gpu/drm/i915/intel_uncore.c

+13 −4
Original line number Diff line number Diff line
@@ -345,6 +345,7 @@ intel_uncore_fw_release_timer(struct hrtimer *timer) 
	return HRTIMER_NORESTART;

}



/* Note callers must have acquired the PUNIT->PMIC bus, before calling this. */

static void intel_uncore_forcewake_reset(struct drm_i915_private *dev_priv,

					 bool restore)

{
@@ -353,6 +354,8 @@ static void intel_uncore_forcewake_reset(struct drm_i915_private *dev_priv, 
	int retry_count = 100;

	enum forcewake_domains fw, active_domains;



	iosf_mbi_assert_punit_acquired();



	/* Hold uncore.lock across reset to prevent any register access

	 * with forcewake not set correctly. Wait until all pending

	 * timers are run before holding.
@@ -532,14 +535,18 @@ 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)
@@ -1419,12 +1426,14 @@ 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();

}



static const struct reg_whitelist {

drivers/gpu/drm/i915/selftests/intel_uncore.c

+3 −0
Original line number Diff line number Diff line
@@ -148,7 +148,10 @@ static int intel_uncore_check_forcewake_domains(struct drm_i915_private *dev_pri 
	for_each_set_bit(offset, valid, FW_RANGE) {

		i915_reg_t reg = { offset };



		iosf_mbi_punit_acquire();

		intel_uncore_forcewake_reset(dev_priv, false);

		iosf_mbi_punit_release();



		check_for_unclaimed_mmio(dev_priv);



		(void)I915_READ(reg);