[PATCH] drm: Print some debug/error info during DP dual mode detect

[Ville Syrjälä]

On Wed, Oct 26, 2016 at 05:50:08PM +0300, Imre Deak wrote:
> There's at least one LSPCON device that occasionally returns an unexpected
> adaptor ID which leads to a failed detect. Print some debug info to help
> debugging this and future cases. Also print an error for an unexpected
> adaptor ID, so users can report it.
> 
> Cc: dri-devel at lists.freedesktop.org
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/drm_dp_dual_mode_helper.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> index 488355b..a0e603b 100644
> --- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> @@ -142,6 +142,11 @@ static bool is_hdmi_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
>  		      sizeof(dp_dual_mode_hdmi_id)) == 0;
>  }
>  
> +static bool is_type1_adaptor(uint8_t adaptor_id)
> +{
> +	return adaptor_id == 0 || adaptor_id == 0xff;
> +}
> +
>  static bool is_type2_adaptor(uint8_t adaptor_id)
>  {
>  	return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
> @@ -193,6 +198,8 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
>  	 */
>  	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
>  				    hdmi_id, sizeof(hdmi_id));
> +	DRM_DEBUG_KMS("DP dual mode HDMI ID: %*pE (err %zd)\n",
> +		      ret ? 0 : (int)sizeof(hdmi_id), hdmi_id, ret);

What does that %*pE print with size==0, nothing?

>  	if (ret)
>  		return DRM_DP_DUAL_MODE_UNKNOWN;
>  
> @@ -210,6 +217,8 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
>  	 */
>  	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
>  				    &adaptor_id, sizeof(adaptor_id));
> +	DRM_DEBUG_KMS("DP dual mode adaptor ID: %02x (err %zd)\n",
> +		      adaptor_id, ret);
>  	if (ret == 0) {
>  		if (is_lspcon_adaptor(hdmi_id, adaptor_id))
>  			return DRM_DP_DUAL_MODE_LSPCON;
> @@ -219,6 +228,10 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
>  			else
>  				return DRM_DP_DUAL_MODE_TYPE2_DVI;
>  		}
> +		if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
                                                     ^^^^^^^^^^^^^^^^^^^^^^^^
I take it that was to account for the broken adaptors that ignore the
offset?

> +			DRM_ERROR("Unexpected DP dual mode adapter ID %02x\n",
> +				  adaptor_id);

s/adapter/adaptor/ since that's what the spec called it, and I continued
down the same path to not confuse it the the i2c adapter.

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

> +
>  	}
>  
>  	if (is_hdmi_adaptor(hdmi_id))
> -- 
> 2.5.0

-- 
Ville Syrjälä
Intel OTC