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: <ade54ddd-79ea-4335-9058-c17e4525e83f@huawei.com>
Date: Thu, 27 Feb 2025 21:46:10 +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 Tue, Feb 25, 2025 at 09:57:17PM +0800, Yongbang Shi wrote:
>>> On Mon, 24 Feb 2025 at 16:03, Yongbang Shi <shiyongbang@...wei.com> wrote:
>>>>> 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.I
>>> It should be userspace, who triggers the enable/disable (or it should
>>> be the in-kernel fbdev / fbcon, which interface through the generic
>>> drm_fbdev client).
>> Right, I knew it. When I insmode my driver firstly (or restart display service), it will call disable, modeset and enable,
>> by user, but it won't call when HPD triggered .
> - Is HPD even properly delivered to userspace? What kind of compsitor
>    are you using? Is .detect working properly and reporting a correct
>    plug-in state?

Thanks for your answering. I'm not very good understanding about userspace in framework. In my opinion, when I call
this drm_connector_helper_hpd_irq_event(), the HPD will deliver to userspace.
I use Xorg, and the display service is GDM.
The .detect is called and the getting modes info is correct.
I find that it would only trigger(disable, modeset and enable), when I changed resolutions, restart display service and insmod driver.