[PATCH 9/9] drm/i915/bxt: Enable IPC support

[Mahesh Kumar]

From: "Kumar, Mahesh" <mahesh1.kumar at intel.com>

This patch adds IPC support for platforms. This patch enables IPC
only for BXT/KBL platform as for SKL recommendation is to keep it disabled.
IPC (Isochronous Priority Control) is the hardware feature, which
dynamically controls the memory read priority of Display.

When IPC is enabled, plane read requests are sent at high priority until
filling above the transition watermark, then the requests are sent at
lower priority until dropping below the level 0 watermark.
The lower priority requests allow other memory clients to have better
memory access. When IPC is disabled, all plane read requests are sent at
high priority.

Changes since V1:
 - Remove commandline parameter to disable ipc
 - Address Paulo's comments
Changes since V2:
 - Address review comments
 - Set ipc_enabled flag
Changes since V3:
 - move ipc_enabled flag assignment inside intel_ipc_enable function
Changes since V4:
 - Re-enable IPC after suspend/resume
Changes since V5:
 - Enable IPC for all gen >=9 except SKL

Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c      |  4 +++-
 drivers/gpu/drm/i915/i915_reg.h      |  1 +
 drivers/gpu/drm/i915/intel_display.c |  1 +
 drivers/gpu/drm/i915/intel_drv.h     |  1 +
 drivers/gpu/drm/i915/intel_pm.c      | 16 ++++++++++++++++
 5 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 9167a73f3c69..78332b0bc7a4 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1334,7 +1334,7 @@ int i915_driver_load(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	intel_runtime_pm_enable(dev_priv);
 
-	dev_priv->ipc_enabled = false;
+	intel_enable_ipc(dev_priv);
 
 	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG))
 		DRM_INFO("DRM_I915_DEBUG enabled\n");
@@ -2600,6 +2600,8 @@ static int intel_runtime_resume(struct device *kdev)
 
 	enable_rpm_wakeref_asserts(dev_priv);
 
+	intel_enable_ipc(dev_priv);
+
 	if (ret)
 		DRM_ERROR("Runtime resume failed, disabling it (%d)\n", ret);
 	else
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 64cc674b652a..09af90f8cd0a 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6728,6 +6728,7 @@ enum {
 #define  DISP_FBC_WM_DIS		(1<<15)
 #define DISP_ARB_CTL2	_MMIO(0x45004)
 #define  DISP_DATA_PARTITION_5_6	(1<<6)
+#define  DISP_IPC_ENABLE		(1<<3)
 #define DBUF_CTL	_MMIO(0x45008)
 #define  DBUF_POWER_REQUEST		(1<<31)
 #define  DBUF_POWER_STATE		(1<<30)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 4e03ca6c946f..4769a241b5fb 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15694,6 +15694,7 @@ void intel_display_resume(struct drm_device *dev)
 	if (!ret)
 		ret = __intel_display_resume(dev, state, &ctx);
 
+	intel_enable_ipc(dev_priv);
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index d17a32437f07..d90b239bd85d 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1883,6 +1883,7 @@ bool ilk_disable_lp_wm(struct drm_device *dev);
 int sanitize_rc6_option(struct drm_i915_private *dev_priv, int enable_rc6);
 int skl_check_pipe_max_pixel_rate(struct intel_crtc *intel_crtc,
 				  struct intel_crtc_state *cstate);
+void intel_enable_ipc(struct drm_i915_private *dev_priv);
 static inline int intel_enable_rc6(void)
 {
 	return i915.enable_rc6;
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 7d624fac8554..de2f0044bc88 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5770,6 +5770,22 @@ void intel_update_watermarks(struct intel_crtc *crtc)
 		dev_priv->display.update_wm(crtc);
 }
 
+void intel_enable_ipc(struct drm_i915_private *dev_priv)
+{
+	u32 val;
+
+	dev_priv->ipc_enabled = false;
+	if (INTEL_GEN(dev_priv) < 9 || IS_SKYLAKE(dev_priv))
+		return;
+
+	val = I915_READ(DISP_ARB_CTL2);
+
+	val |= DISP_IPC_ENABLE;
+
+	I915_WRITE(DISP_ARB_CTL2, val);
+	dev_priv->ipc_enabled = true;
+}
+
 /*
  * Lock protecting IPS related data structures
  */
-- 
2.13.0