drm/i915: Only grab correct forcewake for the engine with execlists

Rather than blindly waking up all forcewake domains on command
submission, we can teach each engine what is (or are) the correct
one to take.

On platforms with multiple forcewake domains like VLV, CHV, SKL
and BXT, this has the potential of lowering the GPU and CPU
power use and submission latency.

To implement it we add a function named
intel_uncore_forcewake_for_reg whose purpose is to query which
forcewake domains need to be taken to read or write a specific
register with raw mmio accessors.

These enables the execlists engine setup  to query which
forcewake domains are relevant per engine on the currently
running platform.

v2:
  * Kerneldoc.
  * Split from intel_uncore.c macro extraction, WARN_ON,
    no warns on old platforms. (Chris Wilson)

v3:
  * Single domain per engine, mention all registers,
    bi-directional function and a new name, fix handling
    of gen6 and gen7 writes. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1460468251-14069-1-git-send-email-tvrtko.ursulin@linux.intel.com

1 files changed, 108 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 41dd30f6ddbb..24b0a9ae3df3 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1772,3 +1772,111 @@ intel_uncore_arm_unclaimed_mmio_detection(struct drm_i915_private *dev_priv)
 
 	return false;
 }
+
+static enum forcewake_domains
+intel_uncore_forcewake_for_read(struct drm_i915_private *dev_priv,
+				i915_reg_t reg)
+{
+	enum forcewake_domains fw_domains;
+
+	if (intel_vgpu_active(dev_priv->dev))
+		return 0;
+
+	switch (INTEL_INFO(dev_priv)->gen) {
+	case 9:
+		fw_domains = __gen9_reg_read_fw_domains(i915_mmio_reg_offset(reg));
+		break;
+	case 8:
+		if (IS_CHERRYVIEW(dev_priv))
+			fw_domains = __chv_reg_read_fw_domains(i915_mmio_reg_offset(reg));
+		else
+			fw_domains = __gen6_reg_read_fw_domains(i915_mmio_reg_offset(reg));
+		break;
+	case 7:
+	case 6:
+		if (IS_VALLEYVIEW(dev_priv))
+			fw_domains = __vlv_reg_read_fw_domains(i915_mmio_reg_offset(reg));
+		else
+			fw_domains = __gen6_reg_read_fw_domains(i915_mmio_reg_offset(reg));
+		break;
+	default:
+		MISSING_CASE(INTEL_INFO(dev_priv)->gen);
+	case 5: /* forcewake was introduced with gen6 */
+	case 4:
+	case 3:
+	case 2:
+		return 0;
+	}
+
+	WARN_ON(fw_domains & ~dev_priv->uncore.fw_domains);
+
+	return fw_domains;
+}
+
+static enum forcewake_domains
+intel_uncore_forcewake_for_write(struct drm_i915_private *dev_priv,
+				 i915_reg_t reg)
+{
+	enum forcewake_domains fw_domains;
+
+	if (intel_vgpu_active(dev_priv->dev))
+		return 0;
+
+	switch (INTEL_INFO(dev_priv)->gen) {
+	case 9:
+		fw_domains = __gen9_reg_write_fw_domains(i915_mmio_reg_offset(reg));
+		break;
+	case 8:
+		if (IS_CHERRYVIEW(dev_priv))
+			fw_domains = __chv_reg_write_fw_domains(i915_mmio_reg_offset(reg));
+		else
+			fw_domains = __gen8_reg_write_fw_domains(i915_mmio_reg_offset(reg));
+		break;
+	case 7:
+	case 6:
+		fw_domains = FORCEWAKE_RENDER;
+		break;
+	default:
+		MISSING_CASE(INTEL_INFO(dev_priv)->gen);
+	case 5:
+	case 4:
+	case 3:
+	case 2:
+		return 0;
+	}
+
+	WARN_ON(fw_domains & ~dev_priv->uncore.fw_domains);
+
+	return fw_domains;
+}
+
+/**
+ * intel_uncore_forcewake_for_reg - which forcewake domains are needed to access
+ * 				    a register
+ * @dev_priv: pointer to struct drm_i915_private
+ * @reg: register in question
+ * @op: operation bitmask of FW_REG_READ and/or FW_REG_WRITE
+ *
+ * Returns a set of forcewake domains required to be taken with for example
+ * intel_uncore_forcewake_get for the specified register to be accessible in the
+ * specified mode (read, write or read/write) with raw mmio accessors.
+ *
+ * NOTE: On Gen6 and Gen7 write forcewake domain (FORCEWAKE_RENDER) requires the
+ * callers to do FIFO management on their own or risk losing writes.
+ */
+enum forcewake_domains
+intel_uncore_forcewake_for_reg(struct drm_i915_private *dev_priv,
+			       i915_reg_t reg, unsigned int op)
+{
+	enum forcewake_domains fw_domains = 0;
+
+	WARN_ON(!op);
+
+	if (op & FW_REG_READ)
+		fw_domains = intel_uncore_forcewake_for_read(dev_priv, reg);
+
+	if (op & FW_REG_WRITE)
+		fw_domains |= intel_uncore_forcewake_for_write(dev_priv, reg);
+
+	return fw_domains;
+}