[Intel-gfx] [PATCH] drm/i915: Add DPI FIFO empty status check

[Ville Syrjälä]

On Wed, Dec 09, 2015 at 05:05:52PM +0530, Deepak M wrote:
> From: Gaurav K Singh <gaurav.k.singh at intel.com>
> 
> Before sending TURN ON packet,check the DPI
> FIFO empty status.
> 
> v2: Change in commit message
>     Checking for FIFO empty  only during TURN ON packet.
> v3: Adding a new function for DPI FIFO empty check
> 
> Signed-off-by: Gaurav K Singh <gaurav.k.singh at intel.com>
> Signed-off-by: Deepak M <m.deepak at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dsi.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index 170ae6f..eff982b 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -60,6 +60,17 @@ static void wait_for_dsi_fifo_empty(struct intel_dsi *intel_dsi, enum port port)
>  		DRM_ERROR("DPI FIFOs are not empty\n");
>  }
>  
> +static void wait_for_dpi_fifo_empty(struct intel_dsi *intel_dsi, enum port port)
> +{
> +	struct drm_encoder *encoder = &intel_dsi->base.base;
> +	struct drm_device *dev = encoder->dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;

Passing in intel_dsi just to dig out the dev_priv again seems a bit
pointless. Could just pass dev_priv directly. But I guess it matches the
already existing functions. 

BTW for future reference, we would rather see to_i915(<whatever>)
instead of <whatever>->dev_private.

Anyway, the patch seems to do what it says. I can't really judge
whether it's the right thing to do though.

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> +
> +	if (wait_for((I915_READ(MIPI_GEN_FIFO_STAT(port)) & DPI_FIFO_EMPTY)
> +					== DPI_FIFO_EMPTY, 50))
> +		DRM_ERROR("Timeout waiting for DPI FIFO empty\n");
> +}
> +
>  static void write_data(struct drm_i915_private *dev_priv, u32 reg,
>  		       const u8 *data, u32 len)
>  {
> @@ -443,8 +454,10 @@ static void intel_dsi_enable(struct intel_encoder *encoder)
>  			I915_WRITE(MIPI_MAX_RETURN_PKT_SIZE(port), 8 * 4);
>  	} else {
>  		msleep(20); /* XXX */
> -		for_each_dsi_port(port, intel_dsi->ports)
> +		for_each_dsi_port(port, intel_dsi->ports) {
> +			wait_for_dpi_fifo_empty(intel_dsi, port);
>  			dpi_send_cmd(intel_dsi, TURN_ON, false, port);
> +		}
>  		msleep(100);
>  
>  		drm_panel_enable(intel_dsi->panel);
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC