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

[Yongbang Shi]

> On Mon, Mar 03, 2025 at 01:02:44PM +0800, Yongbang Shi wrote:
> > > On Sat, 1 Mar 2025 at 11:54, Yongbang Shi <shiyongbang@xxxxxxxxxx> 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@xxxxxxxxxx> 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?
> Yes.

I'm sorry for that, just wanna make sure one more thing. I found if I only set the VGA connector's status to disconnected when HPD plugged in, it won't be active.

And If I add drm_cleanup_connector() for VGA, it work. So is this okay that I use this cleanup in HPD?


> > > > 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!