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Commit 7909c7f1 authored by Padmanabhan Komanduru's avatar Padmanabhan Komanduru
Browse files

drm/msm/dp: downshift the link rate during link training logic 



For the link training related tests during Link CTS, there can
be a need to downshift the link rate level lower than the
minimum link rate needed to support a given display resolution.
This is needed both in the HPD high and HPD IRQ path. The Link
Training flow chart in the spec doesn't insist on limiting the
downshift to the minimum required link rate for the resolution.
Hence, allow the complete downshift of the link rate till 1.62
Ghz if needed.

Change-Id: I91135c315c1b6c252cc8751da429a15d8b92ec9f
Signed-off-by: default avatarPadmanabhan Komanduru <pkomandu@codeaurora.org>
parent 8cf0c22b

drivers/gpu/drm/msm/dp/dp_ctrl.c

+8 −20
Original line number Diff line number Diff line
@@ -860,40 +860,24 @@ static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl) 
static int dp_ctrl_link_rate_down_shift(struct dp_ctrl_private *ctrl)

{

	int ret = 0;

	u32 min_req_link_rate_khz;

	u32 new_proposed_link_bw_code;

	u32 new_proposed_link_rate_khz;



	if (!ctrl)

		return -EINVAL;



	min_req_link_rate_khz = ctrl->panel->get_min_req_link_rate(ctrl->panel);



	switch (ctrl->link->link_params.bw_code) {

	case DP_LINK_BW_8_1:

		new_proposed_link_bw_code = DP_LINK_BW_5_4;

		ctrl->link->link_params.bw_code = DP_LINK_BW_5_4;

		break;

	case DP_LINK_BW_5_4:

		new_proposed_link_bw_code = DP_LINK_BW_2_7;

		ctrl->link->link_params.bw_code = DP_LINK_BW_2_7;

		break;

	case DP_LINK_BW_2_7:

	case DP_LINK_BW_1_62:

	default:

		new_proposed_link_bw_code = DP_LINK_BW_1_62;

		ctrl->link->link_params.bw_code = DP_LINK_BW_1_62;

		break;

	};



	new_proposed_link_rate_khz = drm_dp_bw_code_to_link_rate(

						new_proposed_link_bw_code);



	pr_debug("new proposed link rate=%d khz\n", new_proposed_link_rate_khz);

	pr_debug("min required link rate=%d khz\n", min_req_link_rate_khz);



	if (new_proposed_link_rate_khz >= min_req_link_rate_khz)

		ctrl->link->link_params.bw_code = new_proposed_link_bw_code;

	else

		pr_debug("can't go below min required link rate\n");



	pr_debug("new bw code=0x%x\n", ctrl->link->link_params.bw_code);



	return ret;
@@ -1165,8 +1149,12 @@ static int dp_ctrl_handle_sink_request(struct dp_ctrl *dp_ctrl, 
	ctrl = container_of(dp_ctrl, struct dp_ctrl_private, dp_ctrl);



	do {

		if (ret == -EAGAIN)

		if (ret == -EAGAIN) {

			/* try with lower link rate */

			dp_ctrl_link_rate_down_shift(ctrl);



			ctrl->catalog->mainlink_ctrl(ctrl->catalog, false);

		}



		ctrl->catalog->phy_lane_cfg(ctrl->catalog,

			ctrl->orientation, ctrl->link->link_params.lane_count);