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: <CAA8EJpqHmhUxLE57XNeh-nVtSP7WvtBE=FiFWk9kqM_P+AC=0A@mail.gmail.com>
Date: Mon, 24 Feb 2025 18:16:24 +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 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).

-- 
With best wishes
Dmitry