On Thursday 13 October 2016 04:49 PM, Maarten Lankhorst wrote:
Op 13-10-16 om 12:58 schreef Kumar, Mahesh:
From: Mahesh Kumar <mahesh1.ku...@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 is disabled.
IPC (Isochronous Priority Control) is the hardware feature, which
dynamically controles 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

Signed-off-by: Mahesh Kumar <mahesh1.ku...@intel.com>
  drivers/gpu/drm/i915/i915_drv.c  |  2 ++
  drivers/gpu/drm/i915/i915_reg.h  |  1 +
  drivers/gpu/drm/i915/intel_drv.h |  1 +
  drivers/gpu/drm/i915/intel_pm.c  | 15 +++++++++++++++
  4 files changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index b5f601c..58abbaa 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1415,6 +1415,8 @@ int i915_driver_load(struct pci_dev *pdev, const struct 
pci_device_id *ent)
intel_runtime_pm_enable(dev_priv); + intel_enable_ipc(dev_priv);
        /* Everything is in place, we can now relax! */
        DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
                 driver.name, driver.major, driver.minor, driver.patchlevel,
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index a9c467c..c9ebf23 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6144,6 +6144,7 @@ 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_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 2c1897b..45b0fa4 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1766,6 +1766,7 @@ void skl_write_plane_wm(struct intel_crtc *intel_crtc,
  uint32_t ilk_pipe_pixel_rate(const struct intel_crtc_state *pipe_config);
  bool ilk_disable_lp_wm(struct drm_device *dev);
  int sanitize_rc6_option(struct drm_i915_private *dev_priv, int enable_rc6);
+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 4263212..543aa5d 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4833,6 +4833,21 @@ void intel_update_watermarks(struct drm_crtc *crtc)
+void intel_enable_ipc(struct drm_i915_private *dev_priv)
+       u32 val;
+       /* enable IPC only for Broxton for now*/
+       if (!IS_BROXTON(dev_priv) || !IS_KABYLAKE(dev_priv))
+               return;
This comment doesn't match the code.
Is it ok to enable IPC right away? Not when the driver is writing the first 
watermarks? (distrust_bios_wm)
And what about suspend/resume, should this flag be set again after resume?

hmm.. comment should have been Broxton/Kabylake.
Yes we can enable IPC at any time. In future BIOS itself may enable IPC. (though I'm not sure about the behavior if WM programmed by BIOS are not correct) We don't reset (save/restore) this during suspend/resume, it's onetime programming.

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