Commit 05646543 authored Apr 11, 2017 by Chris Wilson

drm/i915: Acquire uncore.lock over intel_uncore_wait_for_register()



We acquire the forcewake and use I915_READ_FW instead for the atomic
wait within intel_uncore_wait_for_register. However, this still leaves
us vulnerable to concurrent mmio access to the register, which can cause
system hangs on gen7. The protection is to acquire uncore.lock around
each register, so lets add it back.

v2: Wrap __intel_wait_for_register_fw() to re-use its atomic wait_for
loop and spare adding another for ourselves.
v3: Add might_sleep() annotation

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170411101340.31994-3-chris@chris-wilson.co.uk


Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

parent 02b312d0

drivers/gpu/drm/i915/intel_uncore.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -1662,14 +1662,22 @@ int intel_wait_for_register(struct drm_i915_private *dev_priv,
		u32 value,
		unsigned int timeout_ms)
		{

		unsigned fw =
		intel_uncore_forcewake_for_reg(dev_priv, reg, FW_REG_READ);
		int ret;

		intel_uncore_forcewake_get(dev_priv, fw);
		ret = wait_for_us((I915_READ_FW(reg) & mask) == value, 2);
		intel_uncore_forcewake_put(dev_priv, fw);
		might_sleep();

		spin_lock_irq(&dev_priv->uncore.lock);
		intel_uncore_forcewake_get__locked(dev_priv, fw);

		ret = __intel_wait_for_register_fw(dev_priv,
		reg, mask, value,
		2, 0, NULL);

		intel_uncore_forcewake_put__locked(dev_priv, fw);
		spin_unlock_irq(&dev_priv->uncore.lock);

		if (ret)
		ret = wait_for((I915_READ_NOTRACE(reg) & mask) == value,
		timeout_ms);

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