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Subject: Re: [PATCH v16 4/4] drm/bridge: dw-hdmi: fix bus formats negotiation
 for 8 bit modes
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <fca28594-8d4e-dd2f-93a0-a052cb888d90@baylibre.com>
Date:   Wed, 2 Mar 2022 12:15:48 +0100
Cc:     Paul Boddie <paul@boddie.org.uk>,
        Maxime Ripard <maxime@cerno.tech>,
        Jonas Karlman <jonas@kwiboo.se>,
        David Airlie <airlied@linux.ie>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        linux-mips <linux-mips@vger.kernel.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Paul Cercueil <paul@crapouillou.net>,
        Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
        Robert Foss <robert.foss@linaro.org>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@openphoenux.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
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References: <cover.1645895582.git.hns@goldelico.com>
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 <5da069b6-8a99-79c2-109c-c85715165857@baylibre.com>
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 <fca28594-8d4e-dd2f-93a0-a052cb888d90@baylibre.com>
To:     Neil Armstrong <narmstrong@baylibre.com>
Precedence: bulk

Hi Neil,

> Am 02.03.2022 um 11:25 schrieb Neil Armstrong =
<narmstrong@baylibre.com>:
>=20
>> I added a printk for hdmi->sink_is_hdmi. This returns 1. Which IMHO =
is to be expected
>> since I am using a HDMI connector and panel... So your patch will =
still add the UYVY formats.
>> Either the synposys module inside the jz4780 or the panel does not =
understand them.
>=20
> By selecting the UYVY formats, the driver will enable the colorspace =
converters in the dw-hdmi IP,
> I don't see why it doesn't work here...
>=20
> There is a bit called `Support Color Space Converter` in config0_id:
> bit	|	Name	|	R/W	|	Desc
> 2 	|	csc	| 	R 	|	Indicates if Color Space =
Conversion block is present
>=20
> Could you dump all the config0 bits:
>=20
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D><=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c =
b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 54d8fdad395f..547731482da8 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -3431,6 +3431,7 @@ struct dw_hdmi *dw_hdmi_probe(struct =
platform_device *pdev,
>        pdevinfo.id =3D PLATFORM_DEVID_AUTO;
>=20
>        config0 =3D hdmi_readb(hdmi, HDMI_CONFIG0_ID);
> +       dev_info(dev, "config0: %x\n", config0);
>        config3 =3D hdmi_readb(hdmi, HDMI_CONFIG3_ID);
>=20
>        if (iores && config3 & HDMI_CONFIG3_AHBAUDDMA) {
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D><=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
>=20
> If this bit is missing, this would explain the black screen.

[    9.291011] dw-hdmi-ingenic 10180000.hdmi: config0: bf

Hm. Or is the color-space conversion of the sw-hdmi module inside the =
jz4780 broken
or not configured properly?

(cross-checked: RGB mode still works if I force hdmi->sink_is_hdmi =3D =
false)

BR and thanks,
Nikolaus