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: <6506e448-3851-436f-9354-42f9ef844d27@huawei.com>
Date: Sat, 1 Mar 2025 16:45:40 +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 Thu, Feb 27, 2025 at 09:46:10PM +0800, Yongbang Shi wrote:
>>> 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.
> You can go to the display settings in GDM. It would be interesting to
> observe if it notes the second monitor or not. Last, but not least, you
> can use a simple tool like 'xrandr' under your XOrg session to set the
> display resolution.

Thank you for your advice!
Right, there are DP and VGA two monitors. I tried to totally remove the vga connector in driver, the problem is gone.
So do I need to clear the vga connector, if dp is plugged in?
And also, I used xrandr to set modes after 'startx'. Changing resolutions works,
but there are errs when set some low resolutions.