linux-kernel - Re: [PATCH 13/14] drm/bridge: synopsys: Add DW HDMI QP TX controller driver

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Date: Tue, 4 Jun 2024 22:41:10 +0200
From: Sam Ravnborg <sam@...nborg.org>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Sandy Huang <hjc@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	Andy Yan <andy.yan@...k-chips.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Mark Yao <markyao0591@...il.com>, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
	kernel@...labora.com, Alexandre ARNOUD <aarnoud@...com>,
	Luis de Arquer <ldearquer@...il.com>,
	Algea Cao <algea.cao@...k-chips.com>
Subject: Re: [PATCH 13/14] drm/bridge: synopsys: Add DW HDMI QP TX controller
 driver

Hi Cristian.

On Tue, Jun 04, 2024 at 10:32:04PM +0300, Cristian Ciocaltea wrote:
> Hi Sam,
> 
> On 6/1/24 5:32 PM, Sam Ravnborg wrote:
> > Hi Cristian,
> > 
> > a few drive-by comments below.
> > 
> > 	Sam
> > 
> > 
> >> +
> >> +static const struct drm_connector_funcs dw_hdmi_qp_connector_funcs = {
> >> +	.fill_modes = drm_helper_probe_single_connector_modes,
> >> +	.detect = dw_hdmi_connector_detect,
> >> +	.destroy = drm_connector_cleanup,
> >> +	.force = dw_hdmi_qp_connector_force,
> >> +	.reset = drm_atomic_helper_connector_reset,
> >> +	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> >> +	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> >> +};
> >> +
> >> +static int dw_hdmi_qp_bridge_attach(struct drm_bridge *bridge,
> >> +				    enum drm_bridge_attach_flags flags)
> >> +{
> >> +	struct dw_hdmi *hdmi = bridge->driver_private;
> >> +
> >> +	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
> >> +		return drm_bridge_attach(bridge->encoder, hdmi->next_bridge,
> >> +					 bridge, flags);
> >> +
> >> +	return dw_hdmi_connector_create(hdmi, &dw_hdmi_qp_connector_funcs);
> >> +}
> > 
> > Are there any users left that requires the display driver to create the
> > connector?
> > In other words - could this driver fail if DRM_BRIDGE_ATTACH_NO_CONNECTOR
> > is not passed and drop dw_hdmi_connector_create()?
> > 
> > I did not try to verify this - just a naive question.
> 
> I've just tested this and it doesn't work - dw_hdmi_connector_create()
> is still needed.

Hmm, seems the display driver or some other bridge driver fails to
support "DRM_BRIDGE_ATTACH_NO_CONNECTOR".
what other drivers are involved?

Note that my comments here should be seen as potential future
improvements, and do not block the patch from being used.

	Sam