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: <vrsy4hao4qu3hlcbmjyfyibeearhhjgtik3e6o3v2eyzkatdve@kdb7cyvl45tu>
Date: Wed, 26 Feb 2025 08:51:33 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Yongbang Shi <shiyongbang@...wei.com>
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
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?

-- 
With best wishes
Dmitry