drm/i915: reference counted forcewake

Provide a reference count to track the forcewake state of the GPU and
give a safe mechanism for userspace to wake the GT. This also potentially
saves a UC read if the GT is known to be awake already.

The reference count is atomic, but the register access and hardware wake
sequence is protected by struct_mutex.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 52d2306..3b1147d 100644 (file)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -874,7 +874,7 @@ static int i915_cur_delayinfo(struct seq_file *m, void *unused)
                int max_freq;
 
                /* RPSTAT1 is in the GT power well */
-               __gen6_gt_force_wake_get(dev_priv);
+               gen6_gt_force_wake_get(dev_priv);
 
                rpstat = I915_READ(GEN6_RPSTAT1);
                rpupei = I915_READ(GEN6_RP_CUR_UP_EI);
@@ -919,7 +919,7 @@ static int i915_cur_delayinfo(struct seq_file *m, void *unused)
                seq_printf(m, "Max non-overclocked (RP0) frequency: %dMHz\n",
                           max_freq * 50);
 
-               __gen6_gt_force_wake_put(dev_priv);
+               gen6_gt_force_wake_put(dev_priv);
        } else {
                seq_printf(m, "no P-state info available\n");
        }

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index c34a8dd..52e52ce 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -263,7 +263,7 @@ void intel_detect_pch (struct drm_device *dev)
        }
 }
 
-void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
+static void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
 {
        int count;
 
@@ -279,12 +279,38 @@ void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
                udelay(10);
 }
 
-void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
+/*
+ * Generally this is called implicitly by the register read function. However,
+ * if some sequence requires the GT to not power down then this function should
+ * be called at the beginning of the sequence followed by a call to
+ * gen6_gt_force_wake_put() at the end of the sequence.
+ */
+void gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
+{
+       WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+
+       /* Forcewake is atomic in case we get in here without the lock */
+       if (atomic_add_return(1, &dev_priv->forcewake_count) == 1)
+               __gen6_gt_force_wake_get(dev_priv);
+}
+
+static void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
 {
        I915_WRITE_NOTRACE(FORCEWAKE, 0);
        POSTING_READ(FORCEWAKE);
 }
 
+/*
+ * see gen6_gt_force_wake_get()
+ */
+void gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
+{
+       WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+
+       if (atomic_dec_and_test(&dev_priv->forcewake_count))
+               __gen6_gt_force_wake_put(dev_priv);
+}
+
 void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
 {
        int loop = 500;

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 083644e..bafb387 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -709,6 +709,8 @@ typedef struct drm_i915_private {
        struct intel_fbdev *fbdev;
 
        struct drm_property *broadcast_rgb_property;
+
+       atomic_t forcewake_count;
 } drm_i915_private_t;
 
 enum i915_cache_level {
@@ -1329,8 +1331,8 @@ extern void intel_display_print_error_state(struct seq_file *m,
  * must be set to prevent GT core from power down and stale values being
  * returned.
  */
-void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv);
-void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv);
+void gen6_gt_force_wake_get(struct drm_i915_private *dev_priv);
+void gen6_gt_force_wake_put(struct drm_i915_private *dev_priv);
 void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv);
 
 /* We give fast paths for the really cool registers */
@@ -1343,15 +1345,16 @@ void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv);
 static inline u##x i915_read##x(struct drm_i915_private *dev_priv, u32 reg) { \
        u##x val = 0; \
        if (NEEDS_FORCE_WAKE((dev_priv), (reg))) { \
-               __gen6_gt_force_wake_get(dev_priv); \
+               gen6_gt_force_wake_get(dev_priv); \
                val = read##y(dev_priv->regs + reg); \
-               __gen6_gt_force_wake_put(dev_priv); \
+               gen6_gt_force_wake_put(dev_priv); \
        } else { \
                val = read##y(dev_priv->regs + reg); \
        } \
        trace_i915_reg_rw(false, reg, val, sizeof(val)); \
        return val; \
 }
+
 __i915_read(8, b)
 __i915_read(16, w)
 __i915_read(32, l)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 6225c33..edd208e 100644 (file)
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -396,7 +396,6 @@ static void gen6_pm_irq_handler(struct drm_device *dev)
                        I915_WRITE(GEN6_RP_INTERRUPT_LIMITS,
                                   I915_READ(GEN6_RP_INTERRUPT_LIMITS) & ~0x3f0000);
                }
-
        }
 
        gen6_set_rps(dev, new_delay);

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a38fb39..220c3e0 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1540,7 +1540,7 @@ static void sandybridge_blit_fbc_update(struct drm_device *dev)
        u32 blt_ecoskpd;
 
        /* Make sure blitter notifies FBC of writes */
-       __gen6_gt_force_wake_get(dev_priv);
+       gen6_gt_force_wake_get(dev_priv);
        blt_ecoskpd = I915_READ(GEN6_BLITTER_ECOSKPD);
        blt_ecoskpd |= GEN6_BLITTER_FBC_NOTIFY <<
                GEN6_BLITTER_LOCK_SHIFT;
@@ -1551,7 +1551,7 @@ static void sandybridge_blit_fbc_update(struct drm_device *dev)
                         GEN6_BLITTER_LOCK_SHIFT);
        I915_WRITE(GEN6_BLITTER_ECOSKPD, blt_ecoskpd);
        POSTING_READ(GEN6_BLITTER_ECOSKPD);
-       __gen6_gt_force_wake_put(dev_priv);
+       gen6_gt_force_wake_put(dev_priv);
 }
 
 static void ironlake_enable_fbc(struct drm_crtc *crtc, unsigned long interval)
@@ -6973,7 +6973,7 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
         * userspace...
         */
        I915_WRITE(GEN6_RC_STATE, 0);
-       __gen6_gt_force_wake_get(dev_priv);
+       gen6_gt_force_wake_get(dev_priv);
 
        /* disable the counters and set deterministic thresholds */
        I915_WRITE(GEN6_RC_CONTROL, 0);
@@ -7074,7 +7074,7 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
        /* enable all PM interrupts */
        I915_WRITE(GEN6_PMINTRMSK, 0);
 
-       __gen6_gt_force_wake_put(dev_priv);
+       gen6_gt_force_wake_put(dev_priv);
 }
 
 void intel_enable_clock_gating(struct drm_device *dev)