From: Jitao Shi jitao.shi@mediatek.com
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@mediatek.com Reviewed-by: Rex-BC Chen rex-bc.chen@mediatek.com Signed-off-by: Jitao Shi jitao.shi@mediatek.com Signed-off-by: Guillaume Ranquet granquet@baylibre.com --- drivers/gpu/drm/mediatek/mtk_dp.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c index 4789853ec5ff..c056bc3ca9f6 100644 --- a/drivers/gpu/drm/mediatek/mtk_dp.c +++ b/drivers/gpu/drm/mediatek/mtk_dp.c @@ -154,6 +154,8 @@ struct mtk_dp { struct mutex dp_lock;
struct drm_connector *conn; + bool need_debounce; + struct timer_list debounce_timer; };
static struct regmap_config mtk_dp_regmap_config = { @@ -1970,6 +1972,9 @@ 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); @@ -2047,6 +2052,11 @@ static irqreturn_t mtk_dp_hpd_isr_handler(struct mtk_dp *mtk_dp) } train_info->cable_state_change = true;
+ 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; }
@@ -2474,6 +2484,13 @@ 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; @@ -2547,6 +2564,9 @@ 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);
@@ -2559,6 +2579,7 @@ 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);