From: Jitao Shi <jitao.shi@xxxxxxxxxxxx>
>From the DP spec 1.4a chapter 3.3, upstream devices should implement
HPD signal de-bouncing on an external connection.
A period of 100ms should be used to detect an HPD connect event.
To cover these cases, HPD de-bounce should be implemented only after
HPD low has been detected for at least 100ms.
Therefore,
1. If HPD is low (which means plugging out) for longer than 100ms:
we need to do de-bouncing (which means we need to wait for 100ms).
2. If HPD low is for less than 100ms:
we don't need to care about the de-bouncing.
In this patch, we start a 100ms timer and use a need_debounce boolean
to implement the feature.
Two cases when HPD is high:
1. If the timer is expired (>100ms):
- need_debounce is 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 (<100ms):
- need_debounce is false.
- When HPD high (plugging event comes), need_debounce will be false
and no need to do de-bouncing.
HPD_______ __________________
| |<- 100ms ->
|____________|
<- 100ms ->
Without HPD de-bouncing, USB-C to HDMI Adapaters will not be detected.
The change has been successfully tested with the following devices:
- 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>
Reviewed-by: Rex-BC Chen <rex-bc.chen@xxxxxxxxxxxx>
Signed-off-by: Jitao Shi <jitao.shi@xxxxxxxxxxxx>
Signed-off-by: Guillaume Ranquet <granquet@xxxxxxxxxxxx>
Signed-off-by: Bo-Chen Chen <rex-bc.chen@xxxxxxxxxxxx>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
---
drivers/gpu/drm/mediatek/mtk_dp.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 80d7d6488105..80dd2b999463 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -94,6 +94,8 @@ struct mtk_dp {
bool enabled;
struct drm_connector *conn;
+ bool need_debounce;
+ struct timer_list debounce_timer;
};
static struct regmap_config mtk_dp_regmap_config = {
@@ -1486,6 +1488,9 @@ static irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
{
struct mtk_dp *mtk_dp = dev;
+ if (mtk_dp->need_debounce && mtk_dp->train_info.cable_plugged_in)
+ msleep(100);
+
dev_dbg(mtk_dp->dev, "drm_helper_hpd_irq_event\n");
drm_helper_hpd_irq_event(mtk_dp->bridge.dev);
@@ -1538,6 +1543,10 @@ static irqreturn_t mtk_dp_hpd_event(int hpd, void *dev)
mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
DP_PWR_STATE_BANDGAP_TPLL,
DP_PWR_STATE_MASK);
+
+ mod_timer(&mtk_dp->debounce_timer,
+ jiffies + msecs_to_jiffies(100) - 1);
+ mtk_dp->need_debounce = false;
} else {
mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
DP_PWR_STATE_BANDGAP_TPLL_LANE,
@@ -1962,6 +1971,13 @@ 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;
@@ -2039,6 +2055,9 @@ static int mtk_dp_probe(struct platform_device *pdev)
drm_bridge_add(&mtk_dp->bridge);
+ 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);
@@ -2051,6 +2070,7 @@ 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);
--
2.18.0
