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 | 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 610651dd6365..50a4159095a1 100644 --- a/drivers/gpu/drm/mediatek/mtk_dp.c +++ b/drivers/gpu/drm/mediatek/mtk_dp.c @@ -105,6 +105,8 @@ 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 = { @@ -1551,7 +1553,11 @@ 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); + dev_dbg(mtk_dp->dev, "drm_helper_hpd_irq_event\n"); + drm_helper_hpd_irq_event(mtk_dp->bridge.dev); if (mtk_dp->train_info.cable_state_change) { @@ -1614,6 +1620,12 @@ 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; } @@ -2058,6 +2070,13 @@ 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; @@ -2135,6 +2154,9 @@ 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); @@ -2147,6 +2169,7 @@ 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