Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Content-Type: text/plain;
        charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.21\))
Subject: Re: [PATCH v4 02/10] drm/ingenic: Add support for JZ4780 and HDMI
 output
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <1E10A04A-4A78-4B47-B0FB-1E8C99456DA1@goldelico.com>
Date:   Tue, 28 Sep 2021 14:06:03 +0200
Cc:     Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Kees Cook <keescook@chromium.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Robert Foss <robert.foss@linaro.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Ezequiel Garcia <ezequiel@collabora.com>,
        Harry Wentland <harry.wentland@amd.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        Maxime Ripard <maxime@cerno.tech>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Paul Boddie <paul@boddie.org.uk>, devicetree@vger.kernel.org,
        linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        letux-kernel@openphoenux.org, Jonas Karlman <jonas@kwiboo.se>,
        dri-devel@lists.freedesktop.org
Content-Transfer-Encoding: quoted-printable
Message-Id: <17BF1D7A-2057-448B-9FD2-907DE0EFD281@goldelico.com>
References: <cover.1632761067.git.hns@goldelico.com>
 <68cca888be1894ce45f1a93cfabeb5aa1f88c20a.1632761067.git.hns@goldelico.com>
 <OA150R.JLKJBJP8V7FJ2@crapouillou.net>
 <1E10A04A-4A78-4B47-B0FB-1E8C99456DA1@goldelico.com>
To:     Paul Cercueil <paul@crapouillou.net>
Precedence: bulk

Hi Paul,

> Am 28.09.2021 um 12:21 schrieb H. Nikolaus Schaller =
<hns@goldelico.com>:
>=20
>>> @@ -1492,10 +1555,16 @@ static int ingenic_drm_init(void)
>>> {
>>> 	int err;
>>> +	if (IS_ENABLED(CONFIG_DRM_INGENIC_DW_HDMI)) {
>>> +		err =3D =
platform_driver_register(ingenic_dw_hdmi_driver_ptr);
>>> +		if (err)
>>> +			return err;
>>> +	}
>>=20
>> I don't see why you need to register the ingenic-dw-hdmi driver here. =
Just register it in the ingenic-dw-hdmi driver.
>=20
> Ok, I never though about this (as the code was not from me). We =
apparently just followed the IPU code pattern (learning by example).
>=20
> It indeed looks not necessary and would also avoid the =
ingenic_dw_hdmi_driver_ptr dependency.
>=20
> But: what is ingenic_ipu_driver_ptr then good for?
>=20
> If we can get rid of this as well, we can drop patch 1/10 =
("drm/ingenic: Fix drm_init error path if IPU was registered") =
completely.

A quick test shows that it *is* required. At least if I configure =
everything as modules.
But like you I can't explain why.

Well, just a very rough idea (may be wrong): the bridge chain is not =
like an i2c bus and
clients are not automatically loaded/probed if linked in the device =
tree. Therefore the
consumer (ingenic_drm_drv) must register the "clients" like IPU and =
HDMI.

BR,
Nikolaus