drm/i915: Take forcewake once for the entire GMBUS transaction

As we do many register reads within a very short period of time, hold
the GMBUS powerwell from start to finish.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Weinehall <david.weinehall@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160819164503.17845-1-chris@chris-wilson.co.ukReviewed-by: David Weinehall <david.weinehall@linux.intel.com>

drivers/gpu/drm/i915/intel_i2c.c

@@ -255,67 +255,59 @@ intel_gpio_setup(struct intel_gmbus *bus, unsigned int pin)
 	algo->data = bus;
 }
 
-static int
-gmbus_wait_hw_status(struct drm_i915_private *dev_priv,
-		     u32 gmbus2_status,
-		     u32 gmbus4_irq_en)
+static int gmbus_wait(struct drm_i915_private *dev_priv, u32 status, u32 irq_en)
 {
-	int i;
-	u32 gmbus2 = 0;
 	DEFINE_WAIT(wait);
-
-	if (!HAS_GMBUS_IRQ(dev_priv))
-		gmbus4_irq_en = 0;
+	u32 gmbus2;
+	int ret;
 
 	/* Important: The hw handles only the first bit, so set only one! Since
 	 * we also need to check for NAKs besides the hw ready/idle signal, we
-	 * need to wake up periodically and check that ourselves. */
-	I915_WRITE(GMBUS4, gmbus4_irq_en);
-
-	for (i = 0; i < msecs_to_jiffies_timeout(50); i++) {
-		prepare_to_wait(&dev_priv->gmbus_wait_queue, &wait,
-				TASK_UNINTERRUPTIBLE);
+	 * need to wake up periodically and check that ourselves.
+	 */
+	if (!HAS_GMBUS_IRQ(dev_priv))
+		irq_en = 0;
 
-		gmbus2 = I915_READ_NOTRACE(GMBUS2);
-		if (gmbus2 & (GMBUS_SATOER | gmbus2_status))
-			break;
+	add_wait_queue(&dev_priv->gmbus_wait_queue, &wait);
+	I915_WRITE_FW(GMBUS4, irq_en);
 
-		schedule_timeout(1);
-	}
-	finish_wait(&dev_priv->gmbus_wait_queue, &wait);
+	status |= GMBUS_SATOER;
+	ret = wait_for_us((gmbus2 = I915_READ_FW(GMBUS2)) & status, 2);
+	if (ret)
+		ret = wait_for((gmbus2 = I915_READ_FW(GMBUS2)) & status, 50);
 
-	I915_WRITE(GMBUS4, 0);
+	I915_WRITE_FW(GMBUS4, 0);
+	remove_wait_queue(&dev_priv->gmbus_wait_queue, &wait);
 
 	if (gmbus2 & GMBUS_SATOER)
 		return -ENXIO;
-	if (gmbus2 & gmbus2_status)
-		return 0;
-	return -ETIMEDOUT;
+
+	return ret;
 }
 
 static int
 gmbus_wait_idle(struct drm_i915_private *dev_priv)
 {
+	DEFINE_WAIT(wait);
+	u32 irq_enable;
 	int ret;
 
-	if (!HAS_GMBUS_IRQ(dev_priv))
-		return intel_wait_for_register(dev_priv,
-					       GMBUS2, GMBUS_ACTIVE, 0,
-					       10);
-
 	/* Important: The hw handles only the first bit, so set only one! */
-	I915_WRITE(GMBUS4, GMBUS_IDLE_EN);
+	irq_enable = 0;
+	if (HAS_GMBUS_IRQ(dev_priv))
+		irq_enable = GMBUS_IDLE_EN;
 
-	ret = wait_event_timeout(dev_priv->gmbus_wait_queue,
-				 (I915_READ_NOTRACE(GMBUS2) & GMBUS_ACTIVE) == 0,
-				 msecs_to_jiffies_timeout(10));
+	add_wait_queue(&dev_priv->gmbus_wait_queue, &wait);
+	I915_WRITE_FW(GMBUS4, irq_enable);
 
-	I915_WRITE(GMBUS4, 0);
+	ret = intel_wait_for_register_fw(dev_priv,
+					 GMBUS2, GMBUS_ACTIVE, 0,
+					 10);
 
-	if (ret)
-		return 0;
-	else
-		return -ETIMEDOUT;
+	I915_WRITE_FW(GMBUS4, 0);
+	remove_wait_queue(&dev_priv->gmbus_wait_queue, &wait);
+
+	return ret;
 }
 
 static int
@@ -323,7 +315,7 @@ gmbus_xfer_read_chunk(struct drm_i915_private *dev_priv,
 		      unsigned short addr, u8 *buf, unsigned int len,
 		      u32 gmbus1_index)
 {
-	I915_WRITE(GMBUS1,
+	I915_WRITE_FW(GMBUS1,
 		      gmbus1_index |
 		      GMBUS_CYCLE_WAIT |
 		      (len << GMBUS_BYTE_COUNT_SHIFT) |
@@ -333,12 +325,11 @@ gmbus_xfer_read_chunk(struct drm_i915_private *dev_priv,
 		int ret;
 		u32 val, loop = 0;
 
-		ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_RDY,
-					   GMBUS_HW_RDY_EN);
+		ret = gmbus_wait(dev_priv, GMBUS_HW_RDY, GMBUS_HW_RDY_EN);
 		if (ret)
 			return ret;
 
-		val = I915_READ(GMBUS3);
+		val = I915_READ_FW(GMBUS3);
 		do {
 			*buf++ = val & 0xff;
 			val >>= 8;
@@ -385,8 +376,8 @@ gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv,
 		len -= 1;
 	}
 
-	I915_WRITE(GMBUS3, val);
-	I915_WRITE(GMBUS1,
+	I915_WRITE_FW(GMBUS3, val);
+	I915_WRITE_FW(GMBUS1,
 		      GMBUS_CYCLE_WAIT |
 		      (chunk_size << GMBUS_BYTE_COUNT_SHIFT) |
 		      (addr << GMBUS_SLAVE_ADDR_SHIFT) |
@@ -399,10 +390,9 @@ gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv,
 			val |= *buf++ << (8 * loop);
 		} while (--len && ++loop < 4);
 
-		I915_WRITE(GMBUS3, val);
+		I915_WRITE_FW(GMBUS3, val);
 
-		ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_RDY,
-					   GMBUS_HW_RDY_EN);
+		ret = gmbus_wait(dev_priv, GMBUS_HW_RDY, GMBUS_HW_RDY_EN);
 		if (ret)
 			return ret;
 	}
@@ -460,13 +450,13 @@ gmbus_xfer_index_read(struct drm_i915_private *dev_priv, struct i2c_msg *msgs)
 
 	/* GMBUS5 holds 16-bit index */
 	if (gmbus5)
-		I915_WRITE(GMBUS5, gmbus5);
+		I915_WRITE_FW(GMBUS5, gmbus5);
 
 	ret = gmbus_xfer_read(dev_priv, &msgs[1], gmbus1_index);
 
 	/* Clear GMBUS5 after each index transfer */
 	if (gmbus5)
-		I915_WRITE(GMBUS5, 0);
+		I915_WRITE_FW(GMBUS5, 0);
 
 	return ret;
 }
@@ -478,11 +468,15 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 					       struct intel_gmbus,
 					       adapter);
 	struct drm_i915_private *dev_priv = bus->dev_priv;
+	const unsigned int fw =
+		intel_uncore_forcewake_for_reg(dev_priv, GMBUS0,
+					       FW_REG_READ | FW_REG_WRITE);
 	int i = 0, inc, try = 0;
 	int ret = 0;
 
+	intel_uncore_forcewake_get(dev_priv, fw);
 retry:
-	I915_WRITE(GMBUS0, bus->reg0);
+	I915_WRITE_FW(GMBUS0, bus->reg0);
 
 	for (; i < num; i += inc) {
 		inc = 1;
@@ -496,8 +490,8 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 		}
 
 		if (!ret)
-			ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_WAIT_PHASE,
-						   GMBUS_HW_WAIT_EN);
+			ret = gmbus_wait(dev_priv,
+					 GMBUS_HW_WAIT_PHASE, GMBUS_HW_WAIT_EN);
 		if (ret == -ETIMEDOUT)
 			goto timeout;
 		else if (ret)
@@ -508,7 +502,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 	 * a STOP on the very first cycle. To simplify the code we
 	 * unconditionally generate the STOP condition with an additional gmbus
 	 * cycle. */
-	I915_WRITE(GMBUS1, GMBUS_CYCLE_STOP | GMBUS_SW_RDY);
+	I915_WRITE_FW(GMBUS1, GMBUS_CYCLE_STOP | GMBUS_SW_RDY);
 
 	/* Mark the GMBUS interface as disabled after waiting for idle.
 	 * We will re-enable it at the start of the next xfer,
@@ -519,7 +513,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 			 adapter->name);
 		ret = -ETIMEDOUT;
 	}
-	I915_WRITE(GMBUS0, 0);
+	I915_WRITE_FW(GMBUS0, 0);
 	ret = ret ?: i;
 	goto out;
 
@@ -548,9 +542,9 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 	 * of resetting the GMBUS controller and so clearing the
 	 * BUS_ERROR raised by the slave's NAK.
 	 */
-	I915_WRITE(GMBUS1, GMBUS_SW_CLR_INT);
-	I915_WRITE(GMBUS1, 0);
-	I915_WRITE(GMBUS0, 0);
+	I915_WRITE_FW(GMBUS1, GMBUS_SW_CLR_INT);
+	I915_WRITE_FW(GMBUS1, 0);
+	I915_WRITE_FW(GMBUS0, 0);
 
 	DRM_DEBUG_KMS("GMBUS [%s] NAK for addr: %04x %c(%d)\n",
 			 adapter->name, msgs[i].addr,
@@ -573,7 +567,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 timeout:
 	DRM_DEBUG_KMS("GMBUS [%s] timed out, falling back to bit banging on pin %d\n",
 		      bus->adapter.name, bus->reg0 & 0xff);
-	I915_WRITE(GMBUS0, 0);
+	I915_WRITE_FW(GMBUS0, 0);
 
 	/*
 	 * Hardware may not support GMBUS over these pins? Try GPIO bitbanging
@@ -582,6 +576,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 	ret = -EAGAIN;
 
 out:
+	intel_uncore_forcewake_put(dev_priv, fw);
 	return ret;
 }