Re: [PATCH] drm/mediatek: DP HPD Detect with debounce

Hi, Jitao:

Jitao Shi jitao.shi@mediatek.com 於 2022年1月12日 週三 下午11:01寫道：

DP Spec 1.4a 3.3 requires dp detect the hpd with debounce.

Upstream implementations should implement HPD signal de-bouncing on an external connection. A period of 100ms should be used for detecting an HPD connect event (i.e., the event, “HPD high,” is confirmed only after HPD has been continuously asserted for 100ms). Care should be taken to not implement de-bouncing on an IRQ_HPD and on a downstream device-generated pair of HPD disconnect/reconnect events (typically HPD shall be de-asserted for more than 2ms, but less than 100ms in this case). To cover these cases, HPD de-bounce should be implemented only after HPD low has been detected for 100ms. Timing requirements in this Standard related to the detection of HPD high are to be interpreted as applying from the completion of an implementation-dependent de-bounce period.

Signed-off-by: Jitao Shi jitao.shi@mediatek.com

mtk dp driver has not been upstreamed yet. This patch seems depend on another series [1]. Please describe the dependency information here.

[1] https://patchwork.kernel.org/project/linux-mediatek/list/?series=597485

Regards, Chun-Kuang.

drivers/gpu/drm/mediatek/mtk_dp.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c index a256d55346a2..05f401a024a4 100644 --- a/drivers/gpu/drm/mediatek/mtk_dp.c +++ b/drivers/gpu/drm/mediatek/mtk_dp.c @@ -193,6 +193,8 @@ struct mtk_dp { struct mutex eld_lock; u8 connector_eld[MAX_ELD_BYTES]; struct drm_connector *conn;

•   bool need_debounce;
  

•   struct timer_list debounce_timer;
  

};

enum mtk_dp_sdp_type { @@ -2217,6 +2219,9 @@ 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);
  

@@ -2296,6 +2301,14 @@ static irqreturn_t mtk_dp_hpd_isr_handler(struct mtk_dp *mtk_dp) mtk_dp->train_state = MTK_DP_TRAIN_STATE_STARTUP; } 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;
  

}

@@ -2903,6 +2916,13 @@ static int mtk_dp_register_audio_driver(struct device *dev) return 0; }

+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; @@ -2990,6 +3010,9 @@ 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);
  

•   mtk_dp->bridge.ops =
            DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_HPD;
    drm_bridge_add(&mtk_dp->bridge);
  

@@ -3008,6 +3031,7 @@ static int mtk_dp_remove(struct platform_device *pdev)

    mtk_dp_video_mute(mtk_dp, true);
    mtk_dp_audio_mute(mtk_dp, true);

•   del_timer_sync(&mtk_dp->debounce_timer);
  
    pm_runtime_disable(&pdev->dev);
  
  

-- 2.12.5