linux-kernel - Re: [PATCH v3 drm-dp 7/8] drm/hisilicon/hibmc: Enable this hot plug detect of irq feature

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Message-ID: <6634386b-afc1-4e31-a2f4-9c1afed2d1d8@huawei.com>
Date: Mon, 24 Feb 2025 22:03:20 +0800
From: Yongbang Shi <shiyongbang@...wei.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: <xinliang.liu@...aro.org>, <tiantao6@...ilicon.com>,
	<maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
	<tzimmermann@...e.de>, <airlied@...il.com>, <daniel@...ll.ch>,
	<kong.kongxinwei@...ilicon.com>, <liangjian010@...wei.com>,
	<chenjianmin@...wei.com>, <lidongming5@...wei.com>, <libaihan@...wei.com>,
	<shenjian15@...wei.com>, <shaojijie@...wei.com>,
	<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
	<shiyongbang@...wei.com>
Subject: Re: [PATCH v3 drm-dp 7/8] drm/hisilicon/hibmc: Enable this hot plug
 detect of irq feature

> On Sat, Feb 22, 2025 at 06:35:48PM +0800, Yongbang Shi wrote:
>>>> +static int hibmc_dp_hpd_event(struct drm_client_dev *client)
>>>> +{
>>>> +	struct hibmc_dp *dp = container_of(client, struct hibmc_dp, client);
>>>> +	struct hibmc_drm_private *priv = to_hibmc_drm_private(dp->drm_dev);
>>>> +	struct drm_display_mode *mode = &priv->crtc.state->adjusted_mode;
>>>> +	int ret;
>>>> +
>>>> +	if (dp->hpd_status) {
>>>> +		hibmc_dp_hpd_cfg(&priv->dp);
>>>> +		ret = hibmc_dp_prepare(dp, mode);
>>>> +		if (ret)
>>>> +			return ret;
>>>> +
>>>> +		hibmc_dp_display_en(dp, true);
>>>> +	} else {
>>>> +		hibmc_dp_display_en(dp, false);
>>>> +		hibmc_dp_reset_link(&priv->dp);
>>>> +	}
>>> If I understand this correctly, you are using a separate drm_client to
>>> enable and disable the link & display. Why is it necessary? Existing
>>> drm_clients and userspace compositors use drm framework, they should be
>>> able to turn the display on and off as required.
>>>
>> Thanks for your asking, there are cfg/reset process when the connector 's pluging in/out.
>> We want to cfg DP registers again when the connector changes. Not only dp link training, but also cfg
>> the different video modes into DP registers.
> Why? The link training and mode programming should happen during
> pre_enable / enable stage (legacy or atomic).

Hi Dmitry,

Right, that's what I'm curious about. It won't call encoder enble/disable functions when I triggered HPD.
And I'm sure the drm_connector_helper_hpd_irq_event() is called. So I add a drm_client for it.


>>