Re: [PATCH v5 4/8] drm/i915/bxt: Enable IPC support

[Paulo Zanoni <paulo.r.zanoni@intel.com>]

Em Sex, 2016-11-18 às 20:39 +0530, Mahesh Kumar escreveu:
> 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
> Changes since V2:
>  - Address review comments
>  - Set ipc_enabled flag
> 
> Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.c  |  1 +
>  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, 18 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c
> b/drivers/gpu/drm/i915/i915_drv.c
> index 1b0a589..4074601 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1244,6 +1244,7 @@ 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);

So now we have to places that touch dev_priv->ipc_enabled. This one and
intel_enable_ipc(). Please move that "dev_priv->ipc_enabled = false"
line to inside intel_enable_ipc(). It's much easier to read the code
when there's a single function responsible for setting the appropriate
value to a variable.


Besides, my understanding of your discussion with Maarten in the last
revision of this patch was that we needed to change where
intel_enable_ipc() is called in order to make sure the bit stays
enabled after suspend/resume. If that's not needed, why is it not
needed?

>  
>  	/* Everything is in place, we can now relax! */
>  	DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
> diff --git a/drivers/gpu/drm/i915/i915_reg.h
> b/drivers/gpu/drm/i915/i915_reg.h
> index c70c07a..300418a 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -6076,6 +6076,7 @@ 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 cd132c2..ad542a2 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1745,6 +1745,7 @@ bool skl_ddb_allocation_overlaps(const struct
> skl_ddb_entry **entries,
>  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 df39b50..d8090aa 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4682,6 +4682,21 @@ 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;
> +
> +	if (!(IS_BROXTON(dev_priv) || IS_KABYLAKE(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
>   */
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