Re: [PATCH] drm/i915/dp: Correctly advertise HBR3 for GEN11+

[Manasi Navare <manasi.d.navare@intel.com>]

On Mon, Jun 03, 2019 at 02:49:40PM -0700, matthew.s.atwood@intel.com wrote:
> From: Matt Atwood <matthew.s.atwood@intel.com>
> 
> intel_dp_set_source_rates() calls intel_dp_is_edp(), which is unsafe to
> use before encoder_type is set. This caused GEN11+ to incorrectly strip
> HBR3 from source rates. Move intel_dp_set_source_rates() to after
> encoder_type is set. Add comment to intel_dp_is_edp() describing unsafe
> usages.

May be also add a WARN_ON inside intel_dp_is_edp() for encoder->type
still set to INTEL_OUTPUT_DDI

> 
> Fixes: b265a2a6255f5 ("drm/i915/icl: combo port vswing programming
> changes per BSPEC")
> Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 24b56b2a76c8..a4490bcad684 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -141,6 +141,8 @@ static const u8 valid_dsc_slicecount[] = {1, 2, 4};
>   *
>   * If a CPU or PCH DP output is attached to an eDP panel, this function
>   * will return true, and false otherwise.
> + *
> + * This function is not safe to use prior to encoder type being set.
>   */
>  bool intel_dp_is_edp(struct intel_dp *intel_dp)

IMHO, this comment and WARN_ON like I mentioned above should be a separate
patch since its just a cleanup and no functional change.

Manasi

>  {
> @@ -7342,8 +7344,6 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  		 intel_dig_port->max_lanes, port_name(port)))
>  		return false;
>  
> -	intel_dp_set_source_rates(intel_dp);
> -
>  	intel_dp->reset_link_params = true;
>  	intel_dp->pps_pipe = INVALID_PIPE;
>  	intel_dp->active_pipe = INVALID_PIPE;
> @@ -7388,6 +7388,8 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  			type == DRM_MODE_CONNECTOR_eDP ? "eDP" : "DP",
>  			port_name(port));
>  
> +	intel_dp_set_source_rates(intel_dp);
> +
>  	drm_connector_init(dev, connector, &intel_dp_connector_funcs, type);
>  	drm_connector_helper_add(connector, &intel_dp_connector_helper_funcs);
>  
> -- 
> 2.17.2
> 
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