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Subject: Re: [PATCH v4 10/10] drm/ingenic: add some jz4780 specific features
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <E40D4D33-536F-4218-BEDD-C64539F15D40@goldelico.com>
Date:   Tue, 28 Sep 2021 13:50:13 +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
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References: <cover.1632761067.git.hns@goldelico.com>
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To:     Paul Cercueil <paul@crapouillou.net>
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> Am 28.09.2021 um 12:06 schrieb H. Nikolaus Schaller =
<hns@goldelico.com>:
>=20
>>>=20
>>> +
>>> +	/* RGB output control may be superfluous. */
>>> +	if (soc_info->has_rgbc)
>>> +		regmap_write(priv->map, JZ_REG_LCD_RGBC,
>>> +			     JZ_LCD_RGBC_RGB_FORMAT_ENABLE |
>>> +			     JZ_LCD_RGBC_ODD_RGB |
>>> +			     JZ_LCD_RGBC_EVEN_RGB);
>>=20
>> ingenic-drm only supports RGB output right now, so I guess the =
RGB_FORMAT_ENABLE bit needs to be set in patch [2/10], otherwise patch =
[2/10] cannot state that it adds support for the JZ4780, if it doesn't =
actually work.

interestingly it works without setting anything in this register.

>>=20
>> The other two bits can be dropped, they are already set in =
ingenic_drm_encoder_atomic_mode_set().
>=20
> Ok.

Setting it manually doesn't change anything visible:

root@letux:~# devmem2 0x13050090
/dev/mem opened.
Memory mapped at address 0x77e14000.
Value at address 0x13050090 (0x77e14090): 0x0
root@letux:~# devmem2 0x13050090 w 0x80
/dev/mem opened.
Memory mapped at address 0x77e38000.
Value at address 0x13050090 (0x77e38090): 0x0
Written 0x80; readback 0x80
root@letux:~#=20

Same for 0x130A0090. Maybe this lcdc register
is not used at all - at least for HDMI?

So I'd suggest to drop this whole patch from v5.

BR and thanks,
Nikolaus