Hi, Bo-Chen:
On Fri, 2022-07-01 at 14:28 +0800, Bo-Chen Chen wrote:
> From: Markus Schneider-Pargmann <msp@xxxxxxxxxxxx>
>
> This patch adds a embedded 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
> Jitao shi <jitao.shi@xxxxxxxxxxxx>
>
> Signed-off-by: Markus Schneider-Pargmann <msp@xxxxxxxxxxxx>
> Signed-off-by: Guillaume Ranquet <granquet@xxxxxxxxxxxx>
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@xxxxxxxxxxxx>
> ---
[snip]
> +/*
> + * We need to handle HPD signal in eDP even though eDP is a always
> connected
> + * device. Besides connected status, there is another feature for
> HPD signal -
> + * HPD pulse: it presents an IRQ from sink devices to source devices
> (Refer to
> + * 5.1.4 of DP1.4 spec).
> + */
> +static irqreturn_t mtk_dp_hpd_isr_handler(struct mtk_dp *mtk_dp)
> +{
> + bool connected;
> + bool hpd_connect_sta;
> + u32 irq_status = mtk_dp_swirq_get_clear(mtk_dp) |
> + mtk_dp_hwirq_get_clear(mtk_dp);
> + struct mtk_dp_train_info *train_info = &mtk_dp->train_info;
> +
> + if (irq_status & MTK_DP_HPD_INTERRUPT)
> + train_info->irq_sta.hpd_inerrupt = true;
> + if (irq_status & MTK_DP_HPD_CONNECT)
> + hpd_connect_sta = true;
> + if (irq_status & MTK_DP_HPD_DISCONNECT)
> + train_info->irq_sta.hpd_disconnect = true;
hpd_disconnect is used only in this function, so let it be local
variable.
> +
> + if (!irq_status)
> + return IRQ_HANDLED;
Move this to top of this function.
> +
> + connected = mtk_dp_plug_state(mtk_dp);
> + if (connected || !train_info->cable_plugged_in)
> + train_info->irq_sta.hpd_disconnect = false;
The truth table of (irq_status & MTK_DP_HPD_DISCONNECT, connected,
cable_plugged_in, hpd_disconnect) is
0 0 0 0
0 0 1 0
0 1 0 0
0 1 1 0
1 0 0 0
1 0 1 1
1 1 0 0
1 1 1 0
So the only case that hpd_disconnect is true is
(irq_status & MTK_DP_HPD_DISCONNECT) && !connected && train_info-
>cable_plugged_in)
And train_info->cable_plugged_in is the previous status. The previous
status is connected. And irq_status and connected is the new status.
The new status is disconnected.
I have a question. Why we need both irq_status and connected for new
status? I think connected is enough for new status, so we could ignore
irq_status.
Regards,
CK
> + else if (!connected || train_info->cable_plugged_in)
> + hpd_connect_sta = false;
> +
> + if (!(hpd_connect_sta || train_info->irq_sta.hpd_disconnect))
> + return IRQ_WAKE_THREAD;
> +
> + if (hpd_connect_sta) {
> + hpd_connect_sta = false;
> + train_info->cable_plugged_in = true;
> + } else {
> + train_info->irq_sta.hpd_disconnect = false;
> + train_info->cable_plugged_in = false;
> + }
> + train_info->cable_state_change = true;
> +
> + return IRQ_WAKE_THREAD;
> +}
> +
