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

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Date: Wed, 5 Jun 2024 00:34:57 +0300
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Sam Ravnborg <sam@...nborg.org>
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

On 6/4/24 11:41 PM, Sam Ravnborg wrote:
> 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?

Could it be related to the glue driver (updated in the next patch) which
is also responsible for setting up the encoder?

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

Thanks for the heads up! Will try to get back to this soon and investigate.

Cristian