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

From: Sam Ravnborg <sam@ravnborg.org>
To: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Cc: "Andrzej Hajda" <andrzej.hajda@intel.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Robert Foss" <rfoss@kernel.org>,
	"Laurent Pinchart" <Laurent.pinchart@ideasonboard.com>,
	"Jonas Karlman" <jonas@kwiboo.se>,
	"Jernej Skrabec" <jernej.skrabec@gmail.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"David Airlie" <airlied@gmail.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Sandy Huang" <hjc@rock-chips.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Andy Yan" <andy.yan@rock-chips.com>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Mark Yao" <markyao0591@gmail.com>,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org,
	kernel@collabora.com, "Alexandre ARNOUD" <aarnoud@me.com>,
	"Luis de Arquer" <ldearquer@gmail.com>,
	"Algea Cao" <algea.cao@rock-chips.com>
Subject: Re: [PATCH 13/14] drm/bridge: synopsys: Add DW HDMI QP TX controller driver
Date: Tue, 4 Jun 2024 22:41:10 +0200	[thread overview]
Message-ID: <20240604204110.GA84949@ravnborg.org> (raw)
In-Reply-To: <59519381-2729-4839-9882-65a981a0c551@collabora.com>

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

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