In theory, the different register blocks were meant to be only ever touched when holding either the struct_mutex, mode_config.lock or even a specific localised lock. This does not seem to be the case, and the hardware reacts extremely badly if we attempt to concurrently access two registers within the same cacheline. The HSD suggests that we only need to do this workaround for display range registers. However, upon review we need to serialize the multiple stages in our register write functions - if only for preemption protection. Irrespective of the hardware requirements, the current io functions are a little too loose with respect to the combination of pre- and post-condition testing that we do in conjunction with the actual io. As a result, we may be pre-empted and generate both false-postive and false-negative errors. Note well that this is a "90%" solution, there remains a few direct users of ioread/iowrite which will be fixed up in the next few patches. Since they are more invasive and that this simple change will prevent almost all lockups on Haswell, we kept this patch simple to facilitate backporting to stable. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=63914 Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- drivers/gpu/drm/i915/i915_drv.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c index 613e786..401502d 100644 --- a/drivers/gpu/drm/i915/i915_drv.c +++ b/drivers/gpu/drm/i915/i915_drv.c @@ -1271,21 +1271,21 @@ hsw_unclaimed_reg_check(struct drm_i915_private *dev_priv, u32 reg) #define __i915_read(x, y) \ u##x i915_read##x(struct drm_i915_private *dev_priv, u32 reg) { \ + unsigned long irqflags; \ u##x val = 0; \ + spin_lock_irqsave(&dev_priv->gt_lock, irqflags); \ if (IS_GEN5(dev_priv->dev)) \ ilk_dummy_write(dev_priv); \ if (NEEDS_FORCE_WAKE((dev_priv), (reg))) { \ - unsigned long irqflags; \ - spin_lock_irqsave(&dev_priv->gt_lock, irqflags); \ if (dev_priv->forcewake_count == 0) \ dev_priv->gt.force_wake_get(dev_priv); \ val = read##y(dev_priv->regs + reg); \ if (dev_priv->forcewake_count == 0) \ dev_priv->gt.force_wake_put(dev_priv); \ - spin_unlock_irqrestore(&dev_priv->gt_lock, irqflags); \ } else { \ val = read##y(dev_priv->regs + reg); \ } \ + spin_unlock_irqrestore(&dev_priv->gt_lock, irqflags); \ trace_i915_reg_rw(false, reg, val, sizeof(val)); \ return val; \ } @@ -1298,8 +1298,10 @@ __i915_read(64, q) #define __i915_write(x, y) \ void i915_write##x(struct drm_i915_private *dev_priv, u32 reg, u##x val) { \ + unsigned long irqflags; \ u32 __fifo_ret = 0; \ trace_i915_reg_rw(true, reg, val, sizeof(val)); \ + spin_lock_irqsave(&dev_priv->gt_lock, irqflags); \ if (NEEDS_FORCE_WAKE((dev_priv), (reg))) { \ __fifo_ret = __gen6_gt_wait_for_fifo(dev_priv); \ } \ @@ -1311,6 +1313,7 @@ void i915_write##x(struct drm_i915_private *dev_priv, u32 reg, u##x val) { \ gen6_gt_check_fifodbg(dev_priv); \ } \ hsw_unclaimed_reg_check(dev_priv, reg); \ + spin_unlock_irqrestore(&dev_priv->gt_lock, irqflags); \ } __i915_write(8, b) __i915_write(16, w) -- 1.8.3.2 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
