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

[Yongbang Shi <shiyongbang@huawei.com>]

> On Sat, 1 Mar 2025 at 11:54, Yongbang Shi <shiyongbang@huawei.com> wrote:
>>
>>> On Sat, Mar 01, 2025 at 04:45:40PM +0800, Yongbang Shi wrote:
>>>>> 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@huawei.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?
>>> Unless your hardware can not manage two outputs at the same time, no,
>>> you don't have to. Just check how it behaves on x86 systems. Ideally
>>> your driver should have the same behaviour.
>> Our hardware cannot support two outputs with different timing, so I used the one crtc and one plane that DP and VGA share. And just add a new DP connector
>> with a encoder, just like the previous VGA's code logic. But the HPD problem makes me feel confused, should I change the framwork structure to slove this problem?
> I think registering a single CRTC is a correct way. Then it is logical
> that there is no mode set on the DP when you connect it. The userspace
> can not output any data. However if you disconnect VGA and connect DP
> then it should become active and should output your desktop
> environment.

Okay, Thank you for your guidance. So I need to disconnect VGA when I get the HPD (plugged in) , then
userapce will active and enanble DP, right?


>> And also, I will check whether this driver works good on the x86 server. Right now, I'm testing on arm64 server.
>>
>>>> And also, I used xrandr to set modes after 'startx'. Changing resolutions works,
>>>> but there are errs when set some low resolutions.
>>> That's a separate topic, most likely related to timing or to some other
>>> issues. You can fix that separately (but please do, switching modes
>>> should work).
>> Okay!
>>
>>
>