linux-kernel - Re: [PATCH v8 17/19] drm/mediatek: add hpd debounce

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Date:   Mon, 21 Mar 2022 15:24:52 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     Guillaume Ranquet <granquet@...libre.com>,
        <chunkuang.hu@...nel.org>, <p.zabel@...gutronix.de>,
        <airlied@...ux.ie>, <daniel@...ll.ch>, <robh+dt@...nel.org>,
        <maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
        <tzimmermann@...e.de>, <matthias.bgg@...il.com>,
        <chunfeng.yun@...iatek.com>, <kishon@...com>, <vkoul@...nel.org>,
        <deller@....de>, <ck.hu@...iatek.com>, <jitao.shi@...iatek.com>,
        <angelogioacchino.delregno@...labora.com>
CC:     <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-phy@...ts.infradead.org>, <linux-fbdev@...r.kernel.org>
Subject: Re: [PATCH v8 17/19] drm/mediatek: add hpd debounce

On Fri, 2022-02-18 at 15:54 +0100, Guillaume Ranquet wrote:
> From: Jitao Shi <jitao.shi@...iatek.com>
> 
> Implement the DP HDP debounce described in DP 1.4a 3.3.
> 
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>

Reviewed-by: Rex-BC Chen <rex-bc.chen@...iatek.com>

> ---
>  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);
>