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: <6jx5ldpidy2ycrqognfiv5ttqr5ia4dtbryta3kc2mkndrvvgo@qzuakucz765k>
Date: Mon, 24 Feb 2025 04:52:43 +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 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).

> 
> 

-- 
With best wishes
Dmitry