[Intel-gfx] [PATCH v3 1/2] drm/i915/dp: Helper for checking DDI_BUF_CTL Idle status

[Ville Syrjälä]

On Wed, Jun 24, 2020 at 03:11:07PM -0700, Manasi Navare wrote:
> Modify the helper to add a fixed delay or poll with timeout
> based on platform specification to check for either Idle bit
> set (DDI_BUF_CTL is idle for disable case)
> 
> v2:
> * Use 2 separate functions or idle and active (Ville)
> 
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Imre Deak <imre.deak at intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 884b507c5f55..7d5c8ab88fc4 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -1184,16 +1184,15 @@ static void intel_prepare_hdmi_ddi_buffers(struct intel_encoder *encoder,
>  static void intel_wait_ddi_buf_idle(struct drm_i915_private *dev_priv,
>  				    enum port port)
>  {
> -	i915_reg_t reg = DDI_BUF_CTL(port);
> -	int i;
> -
> -	for (i = 0; i < 16; i++) {
> -		udelay(1);
> -		if (intel_de_read(dev_priv, reg) & DDI_BUF_IS_IDLE)
> -			return;
> +	if (IS_BROXTON(dev_priv)) {
> +		udelay(16);
> +		return;
>  	}
> -	drm_err(&dev_priv->drm, "Timeout waiting for DDI BUF %c idle bit\n",
> -		port_name(port));
> +
> +	if (wait_for_us((intel_de_read(dev_priv, DDI_BUF_CTL(port)) &
> +			 DDI_BUF_IS_IDLE), 600))

Why 600?

> +		drm_err(&dev_priv->drm, "Timeout waiting for DDI BUF %c to get idle\n",
> +			port_name(port));
>  }
>  
>  static u32 hsw_pll_to_ddi_pll_sel(const struct intel_shared_dpll *pll)
> -- 
> 2.19.1

-- 
Ville Syrjälä
Intel