linux-kernel - Re: [PATCH v3 1/6] phy: allwinner: phy-sun6i-mipi-dphy: Support LVDS in combo D-PHY

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Message-ID: <72fba214-010d-498e-957f-f1d042f18edc@szczodrzynski.pl>
Date: Sat, 22 Nov 2025 12:27:04 +0100
From: Kuba Szczodrzyński <kuba@...zodrzynski.pl>
To: Parthiban <parthiban@...umiz.com>, Maxime Ripard <mripard@...nel.org>,
 Samuel Holland <samuel@...lland.org>, Chen-Yu Tsai <wens@...e.org>,
 Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
 linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
 linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, paulk@...-base.io
Subject: Re: [PATCH v3 1/6] phy: allwinner: phy-sun6i-mipi-dphy: Support LVDS
 in combo D-PHY

W dniu 2025-11-20 o 07:24:53, Parthiban pisze:

> Dear Kuba,
>
> Thanks for your efforts.
>
> On 11/16/25 2:47 PM, Kuba Szczodrzyński wrote:
>> Some Allwinner chips (notably the D1s/T113 and the A100) have a "combo
>> MIPI DSI D-PHY" which is required when using single-link LVDS0.
>>
>> In this mode, the DSI peripheral is not used and the PHY is not
>> configured for DSI. Instead, the COMBO_PHY_REGx registers are set to
>> enable LVDS operation.
>>
>> Enable the PHY driver to work in LVDS mode on chips with a combo D-PHY.
>>
>> Also change the SUN50I_COMBO_PHY_REG1 macro names to reflect the correct
>> register name.
>>
>> Signed-off-by: Kuba Szczodrzyński <kuba@...zodrzynski.pl>
>> ---
>>   drivers/phy/allwinner/phy-sun6i-mipi-dphy.c | 70 ++++++++++++++++++++-
>>   1 file changed, 68 insertions(+), 2 deletions(-)
> I tried integrating your changes in A133 display pipeline and I couldn't get the LVDS working.
> Am still narrowing down what is missing in your patch. Driver registration is success and I
> can see /dev/fb0 as well. But nothing on the display itself.
>
> But with below changes from my patch,
>
> diff --git a/drivers/phy/allwinner/phy-sun6i-mipi-dphy.c b/drivers/phy/allwinner/phy-sun6i-mipi-dphy.c
> index 36eab95271b2..d164b2ea5dfd 100644
> --- a/drivers/phy/allwinner/phy-sun6i-mipi-dphy.c
> +++ b/drivers/phy/allwinner/phy-sun6i-mipi-dphy.c
> @@ -314,13 +314,11 @@ static void sun50i_a100_mipi_dphy_tx_power_on(struct sun6i_dphy *dphy)
>          /* Disable sigma-delta modulation. */
>          regmap_write(dphy->regs, SUN50I_DPHY_PLL_REG2, 0);
>   
> -       regmap_update_bits(dphy->regs, SUN6I_DPHY_ANA4_REG,
> -                          SUN6I_DPHY_ANA4_REG_EN_MIPI,
> -                          SUN6I_DPHY_ANA4_REG_EN_MIPI);
> -
>          regmap_update_bits(dphy->regs, SUN50I_COMBO_PHY_REG0,
> +                          SUN50I_COMBO_PHY_REG0_EN_LVDS |
>                             SUN50I_COMBO_PHY_REG0_EN_MIPI |
>                             SUN50I_COMBO_PHY_REG0_EN_COMBOLDO,
> +                          SUN50I_COMBO_PHY_REG0_EN_LVDS |
>                             SUN50I_COMBO_PHY_REG0_EN_MIPI |
>                             SUN50I_COMBO_PHY_REG0_EN_COMBOLDO);
>   
> @@ -528,6 +526,22 @@ static int sun6i_dphy_exit(struct phy *phy)
>          return 0;
>   }
>
> LVDS works fine.
>
> Could you please share the diff of your dts / dtsi?

Hi,
Here's the DTS overlay I used to enable an LVDS panel on T113. You'll need to adapt the panel specification to your particular display.
I did not need to change the phy driver, so this extra requirement might be specific to A133.

/dts-v1/;
/plugin/;

&{/} {
	panel {
		compatible = "panel-lvds";
		data-mapping = "jeida-18";
		ddc-i2c-bus = <&i2c2>;

		port {
			panel_input: endpoint {
				remote-endpoint = <&tcon_lcd0_out_lvds>;
			};
		};
	};
};

&tcon_lcd0 {
	pinctrl-names = "default";
	pinctrl-0 = <&lcd_lvds0_pins>;
};

&tcon_lcd0_out {
	reg = <1>;
	#address-cells = <1>;
	#size-cells = <0>;

	tcon_lcd0_out_lvds: endpoint@0 {
		reg = <0>;
		remote-endpoint = <&panel_input>;
	};
};

Regards
Kuba

>
> Thanks,
> Parthiban