drm/i915: fix up ilk drps/ips locking

We change the drps/ips sw/hw state from different callers: Our own irq
handler, the external intel-ips module and from process context. Most
of these callers don't take any lock at all.

Protect everything by making the mchdev_lock irqsave and grabbing it in
all relevant callsites. Note that we have to convert a few sleeps in the
drps enable/disable code to delays, but alas, I'm not volunteering to
restructure the code around a few work items.

For paranoia add a spin_locked assert to ironlake_set_drps, too.

v2: Move one access inside the lock protection. Caught by the
dev_priv->ips mass-rename ...

v3: Resolve rebase conflict.

Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 11 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 3e203da61c69..d15ea50f5854 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -296,14 +296,22 @@ static void i915_hotplug_work_func(struct work_struct *work)
         drm_helper_hpd_irq_event(dev);
 }
 
+/* defined intel_pm.c */
+extern spinlock_t mchdev_lock;
+
 static void ironlake_handle_rps_change(struct drm_device *dev)
 {
         drm_i915_private_t *dev_priv = dev->dev_private;
         u32 busy_up, busy_down, max_avg, min_avg;
-        u8 new_delay = dev_priv->cur_delay;
+        u8 new_delay;
+        unsigned long flags;
+
+        spin_lock_irqsave(&mchdev_lock, flags);
 
         I915_WRITE16(MEMINTRSTS, I915_READ(MEMINTRSTS));
 
+        new_delay = dev_priv->cur_delay;
+
         I915_WRITE16(MEMINTRSTS, MEMINT_EVAL_CHG);
         busy_up = I915_READ(RCPREVBSYTUPAVG);
         busy_down = I915_READ(RCPREVBSYTDNAVG);
@@ -326,6 +334,8 @@ static void ironlake_handle_rps_change(struct drm_device *dev)
         if (ironlake_set_drps(dev, new_delay))
                 dev_priv->cur_delay = new_delay;
 
+        spin_unlock_irqrestore(&mchdev_lock, flags);
+
         return;
 }