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SubjectRe: [PATCH v10 18/21] drm/mediatek: Add mt8195 Embedded DisplayPort driver
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On Tue, 2022-06-07 at 14:44 +0800, CK Hu wrote:
> 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_handler(struct mtk_dp *mtk_dp)
> > +{
> > + bool training_done = false;
> > + short max_retry = 50;
> > + int ret = 0;
> > +
> > + do {
> > + switch (mtk_dp->train_state) {
> > + case MTK_DP_TRAIN_STATE_STARTUP:
>
> mtk_dp->train_state is initialized as MTK_DP_TRAIN_STATE_STARTUP even
> though HPD ISR does not exist. Does this mean HPD ISR is redundant?
> If
> HPD ISR is not redundant, create a new state MTK_DP_TRAIN_STATE_NONE
> for init state.
>

Hello CK,

I think we don't need MTK_DP_TRAIN_STATE_NONE.
Because it's "DP_TRAIN_STATE" not "DP_STATE", I think it's ok if we
start this state machine with "MTK_DP_TRAIN_STATE_STARTUP".

> > + mtk_dp_state_handler(mtk_dp);
> > + mtk_dp->train_state =
> > MTK_DP_TRAIN_STATE_CHECKCAP;
> > + break;
> > +
> > + case MTK_DP_TRAIN_STATE_CHECKCAP:
> > + if (mtk_dp_parse_capabilities(mtk_dp)) {
> > + mtk_dp->train_info.check_cap_count = 0;
> > + mtk_dp->train_state =
> > MTK_DP_TRAIN_STATE_CHECKEDID;
> > + } else {
> > + mtk_dp->train_info.check_cap_count++;
> > +
> > + if (mtk_dp->train_info.check_cap_count
> > >
> >
> > + MTK_DP_CHECK_SINK_CAP_TIMEOUT_COUNT
> > ) {
> > + mtk_dp-
> > > train_info.check_cap_count = 0;
> >
> > + mtk_dp->train_state =
> > MTK_DP_TRAIN_STATE_DPIDLE;
> > + ret = -ETIMEDOUT;
> > + }
> > + }
> > + break;
> > +
> > + case MTK_DP_TRAIN_STATE_CHECKEDID:
> > + mtk_dp->train_state =
> > MTK_DP_TRAIN_STATE_TRAINING_PRE;
>
> MTK_DP_TRAIN_STATE_CHECKEDID is a redundant state, drop it.
>
> > + break;
> > +
> > + case MTK_DP_TRAIN_STATE_TRAINING_PRE:
> > + mtk_dp_state_handler(mtk_dp);
> > + mtk_dp->train_state =
> > MTK_DP_TRAIN_STATE_TRAINING;
> > + break;
> > +
> > + case MTK_DP_TRAIN_STATE_TRAINING:
> > + ret = mtk_dp_train_start(mtk_dp);
> > + if (ret == 0) {
> > + mtk_dp_video_mute(mtk_dp, true);
> > + mtk_dp->train_state =
> > MTK_DP_TRAIN_STATE_NORMAL;
> > + mtk_dp_fec_enable(mtk_dp, mtk_dp-
> > > has_fec);
> >
> > + } else if (ret != -EAGAIN) {
> > + mtk_dp->train_state =
> > MTK_DP_TRAIN_STATE_DPIDLE;
> > + }
> > + break;
> > + case MTK_DP_TRAIN_STATE_NORMAL:
> > + mtk_dp_state_handler(mtk_dp);
> > + training_done = true;
> > + break;
> > + case MTK_DP_TRAIN_STATE_DPIDLE:
>
> When would this case happen?
>
> Regards,
> CK

Yes, if it's disconnected if we are still training for dp.
or failed to training min spec RBR.

BRs,
Rex
>
> > + break;
> > + default:
> > + break;
> > + }
> > +
> > + if (ret) {
> > + if (ret == -EAGAIN)
> > + continue;
> > + /*
> > + * If we get any other error number, it doesn't
> > + * make any sense to keep iterating.
> > + */
> > + break;
> > + }
> > + } while (!training_done || --max_retry);
> > +
> > + return ret;
> > +}
>
>

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