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SubjectRe: [PATCH v10 18/21] drm/mediatek: Add mt8195 Embedded DisplayPort driver
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Hi, Rex:

On Mon, 2022-05-23 at 12:47 +0200, Guillaume Ranquet wrote:
> From: Markus Schneider-Pargmann <msp@baylibre.com>
>
> This patch adds a DisplayPort driver for the Mediatek mt8195 SoC.
>
> It supports the mt8195, the embedded DisplayPort units. It offers
> DisplayPort 1.4 with up to 4 lanes.
>
> The driver creates a child device for the phy. The child device will
> never exist without the parent being active. As they are sharing a
> register range, the parent passes a regmap pointer to the child so
> that
> both can work with the same register range. The phy driver sets
> device
> data that is read by the parent to get the phy device that can be
> used
> to control the phy properties.
>
> This driver is based on an initial version by
> Jason-JH.Lin <jason-jh.lin@mediatek.com>.
>
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> ---

[snip]

> +
> +static int mtk_dp_train_start(struct mtk_dp *mtk_dp)
> +{
> + int ret = 0;
> + u8 lane_count;
> + u8 link_rate;
> + u8 train_limit;
> + u8 max_link_rate;
> + u8 plug_wait;
> +
> + for (plug_wait = 7; !mtk_dp_plug_state(mtk_dp) && plug_wait >
> 0;
> + --plug_wait)
> + /* Avoid short pulses on the HPD isr */
> + usleep_range(1000, 5000);
> + if (plug_wait == 0) {
> + mtk_dp->train_state = MTK_DP_TRAIN_STATE_DPIDLE;

After return, mtk_dp->train_state would be set to
MTK_DP_TRAIN_STATE_DPIDLE, so drop this.

> + return -ENODEV;
> + }
> +
> + link_rate = mtk_dp->rx_cap[1];
> + lane_count = mtk_dp->rx_cap[2] & 0x1F;
> +
> + mtk_dp->train_info.link_rate = min(mtk_dp->max_linkrate,
> link_rate);
> + mtk_dp->train_info.lane_count = min(mtk_dp->max_lanes,
> lane_count);
> + link_rate = mtk_dp->train_info.link_rate;
> + lane_count = mtk_dp->train_info.lane_count;
> +
> + switch (link_rate) {
> + case MTK_DP_LINKRATE_RBR:
> + case MTK_DP_LINKRATE_HBR:
> + case MTK_DP_LINKRATE_HBR2:
> + case MTK_DP_LINKRATE_HBR25:
> + case MTK_DP_LINKRATE_HBR3:
> + break;
> + default:
> + mtk_dp->train_info.link_rate = MTK_DP_LINKRATE_HBR3;
> + break;
> + };
> +
> + max_link_rate = link_rate;
> + for (train_limit = 6; train_limit > 0; train_limit--) {
> + mtk_dp->train_info.cr_done = false;
> + mtk_dp->train_info.eq_done = false;
> +
> + mtk_dp_train_change_mode(mtk_dp);
> + ret = mtk_dp_train_flow(mtk_dp, link_rate, lane_count);
> + if (ret)
> + return ret;
> +
> + if (!mtk_dp->train_info.cr_done) {
> + switch (link_rate) {
> + case MTK_DP_LINKRATE_RBR:
> + lane_count = lane_count / 2;
> + link_rate = max_link_rate;
> + if (lane_count == 0) {
> + mtk_dp->train_state =
> + MTK_DP_TRAIN_STATE_DPID
> LE;

After return, mtk_dp->train_state would be set to
MTK_DP_TRAIN_STATE_DPIDLE, so drop this.

Regards,
CK

> + return -EIO;
> + }
> + break;
> + case MTK_DP_LINKRATE_HBR:
> + link_rate = MTK_DP_LINKRATE_RBR;
> + break;
> + case MTK_DP_LINKRATE_HBR2:
> + link_rate = MTK_DP_LINKRATE_HBR;
> + break;
> + case MTK_DP_LINKRATE_HBR3:
> + link_rate = MTK_DP_LINKRATE_HBR2;
> + break;
> + default:
> + return -EINVAL;
> + };
> + } else if (!mtk_dp->train_info.eq_done) {
> + if (lane_count == 0)
> + return -EIO;
> +
> + lane_count /= 2;
> + } else {
> + break;
> + }
> + }
> +
> + if (train_limit == 0)
> + return -ETIMEDOUT;
> +
> + return 0;
> +}
> +

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