Therefore,
1. If HPD low (which means plugging out) is more than 100ms,
we need to do de-bouncing (which means we need to wait for 100ms).
2. If HPD low is less than 100ms,
we don't need to care about the de-bouncing.
In this patch, we can see the timer start to count 100ms and clear the
need_debounce to false.
There will be two situation when HPD high:
1. If the timer is expired (which means it's more than 100ms):
- need_debounce will be set as true.
- When HPD high (plugging event comes), need_debounce will be true
and then we need to do de-bouncing (wait for 100ms).
2. If the timer is not expired (which means it's less than 100ms):
- need_debounce keeps as false.
- When HPD high (plugging event comes), need_debounce will be false
and no need to do de-bouncing.
HPD_______ __________________
| |<- 100ms ->
|____________|
<- 100ms ->
Original issue is that we do not implement the HPD de-bouncing and the
device (Dell Adapter - USB-C to HDMI) will not be detected.
After applying this patch, we can detect the device
(Dell Adapter - USB-C to HDMI) successfully.
We test the following devices and they can be detected successfully:
- Dell Adapter - USB-C to HDMI
- Acer 1in1 HDMI dongle
- Ugreen 1in1 HDMI dongle
- innowatt HDMI + USB3 hub
- Acer 2in1 HDMI dongle
- Apple 3in1 HDMI dongle (A2119)
- J5Create 3in1 HDMI dongle (JAC379)
Tested-by: Rex-BC Chen <rex-bc.chen@xxxxxxxxxxxx>
BRs,
Rex
>
> Signed-off-by: Jitao Shi <jitao.shi@xxxxxxxxxxxx>
> Signed-off-by: Guillaume Ranquet <granquet@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/mediatek/mtk_dp.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c
> b/drivers/gpu/drm/mediatek/mtk_dp.c
> index 2a3d5f15b651b..fe91ab8b2fd89 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -178,6 +178,8 @@ struct mtk_dp {
> struct device *codec_dev;
> u8 connector_eld[MAX_ELD_BYTES];
> struct drm_connector *conn;
> + bool need_debounce;
> + struct timer_list debounce_timer;
> };
>
> static struct regmap_config mtk_dp_regmap_config = {
> @@ -1698,6 +1700,9 @@ static irqreturn_t mtk_dp_hpd_event_thread(int
> hpd, void *dev)
> if (event < 0)
> return IRQ_HANDLED;
>
> + if (mtk_dp->need_debounce && mtk_dp-
> >train_info.cable_plugged_in)
> + msleep(100);
> +
> if (mtk_dp->drm_dev) {
> dev_info(mtk_dp->dev, "drm_helper_hpd_irq_event\n");
> drm_helper_hpd_irq_event(mtk_dp->bridge.dev);
> @@ -1776,6 +1781,13 @@ static irqreturn_t
> mtk_dp_hpd_isr_handler(struct mtk_dp *mtk_dp)
> }
> train_info->cable_state_change = true;
>
> + if (train_info->cable_state_change) {
> + if (!train_info->cable_plugged_in) {
> + mod_timer(&mtk_dp->debounce_timer, jiffies +
> msecs_to_jiffies(100) - 1);
> + mtk_dp->need_debounce = false;
> + }
> + }
> +
> return IRQ_WAKE_THREAD;
> }
>
> @@ -2239,6 +2251,13 @@ static const struct drm_bridge_funcs
> mtk_dp_bridge_funcs = {
> .detect = mtk_dp_bdg_detect,
> };
>
> +static void mtk_dp_debounce_timer(struct timer_list *t)
> +{
> + struct mtk_dp *mtk_dp = from_timer(mtk_dp, t, debounce_timer);
> +
> + mtk_dp->need_debounce = true;
> +}
> +
> static int mtk_dp_probe(struct platform_device *pdev)
> {
> struct mtk_dp *mtk_dp;
> @@ -2319,6 +2338,9 @@ static int mtk_dp_probe(struct platform_device
> *pdev)
> else
> mtk_dp->bridge.type = DRM_MODE_CONNECTOR_DisplayPort;
>
> + mtk_dp->need_debounce = true;
> + timer_setup(&mtk_dp->debounce_timer, mtk_dp_debounce_timer, 0);
> +
> pm_runtime_enable(dev);
> pm_runtime_get_sync(dev);
>
> @@ -2332,6 +2354,7 @@ static int mtk_dp_remove(struct platform_device
> *pdev)
> platform_device_unregister(mtk_dp->phy_dev);
>
> mtk_dp_video_mute(mtk_dp, true);
> + del_timer_sync(&mtk_dp->debounce_timer);
>
> pm_runtime_disable(&pdev->dev);
>
