> -----Original Message-----
> From: Nautiyal, Ankit K <ankit.k.nautiyal@xxxxxxxxx>
> Sent: Monday, November 8, 2021 11:54 AM
> To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Shankar, Uma <uma.shankar@xxxxxxxxx>; Sharma, Swati2
> <swati2.sharma@xxxxxxxxx>
> Subject: [PATCH v2 2/2] drm/i915/dp: For PCON TMDS mode set only the relavant
> bits in config DPCD
>
> Currently we reset the whole PCON linkConfig DPCD to set the TMDS mode.
> This also resets the Source control bit and HDMI link enable bit and goes to
> autonomous mode of operation, which is seen to spoil the PCONs internal state.
>
> This patch avoids resetting the PCON link config register and sets only the source
> control bit, with FRL Enable bit set to 0 (TMDS mode) in the configuration DPCD. It
> then enables the HDMI Link Enable bit.
>
> v2: Removed the redundant resetting of the bits as the buffer is already initialized to
> 0. (Uma) Updated comments and commit message.
Looks Good to me.
Reviewed-by: Uma Shankar <uma.shankar@xxxxxxxxx>
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_dp.c | 24 +++++++++++++++++++++++-
> 1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index f5fd106e555c..a0ff16bc18f5 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2287,6 +2287,28 @@ static bool intel_dp_is_hdmi_2_1_sink(struct intel_dp
> *intel_dp)
> return false;
> }
>
> +static
> +int intel_dp_pcon_set_tmds_mode(struct intel_dp *intel_dp) {
> + int ret;
> + u8 buf = 0;
> +
> + /* Set PCON source control mode */
> + buf |= DP_PCON_ENABLE_SOURCE_CTL_MODE;
> +
> + ret = drm_dp_dpcd_writeb(&intel_dp->aux,
> DP_PCON_HDMI_LINK_CONFIG_1, buf);
> + if (ret < 0)
> + return ret;
> +
> + /* Set HDMI LINK ENABLE */
> + buf |= DP_PCON_ENABLE_HDMI_LINK;
> + ret = drm_dp_dpcd_writeb(&intel_dp->aux,
> DP_PCON_HDMI_LINK_CONFIG_1, buf);
> + if (ret < 0)
> + return ret;
> +
> + return 0;
> +}
> +
> void intel_dp_check_frl_training(struct intel_dp *intel_dp) {
> struct drm_i915_private *dev_priv = dp_to_i915(intel_dp); @@ -2305,7
> +2327,7 @@ void intel_dp_check_frl_training(struct intel_dp *intel_dp)
> int ret, mode;
>
> drm_dbg(&dev_priv->drm, "Couldn't set FRL mode, continuing with
> TMDS mode\n");
> - ret = drm_dp_pcon_reset_frl_config(&intel_dp->aux);
> + ret = intel_dp_pcon_set_tmds_mode(intel_dp);
> mode = drm_dp_pcon_hdmi_link_mode(&intel_dp->aux, NULL);
>
> if (ret < 0 || mode != DP_PCON_HDMI_MODE_TMDS)
> --
> 2.25.1
