linux-kernel - Re: [PATCH] arm64: dts: mediatek: mt8390-genio-common: Force ssusb2 dual role mode to host

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Message-ID: <eb350c96-379a-46db-8a54-e1b9c71be431@collabora.com>
Date: Thu, 24 Apr 2025 09:24:38 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Nícolas F. R. A. Prado <nfraprado@...labora.com>,
 Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Matthias Brugger
 <matthias.bgg@...il.com>, kernel@...labora.com, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] arm64: dts: mediatek: mt8390-genio-common: Force ssusb2
 dual role mode to host

Il 23/04/25 22:48, Nícolas F. R. A. Prado ha scritto:
> On Mon, Mar 31, 2025 at 11:25:52AM +0200, Louis-Alexis Eyraud wrote:
>> On the Mediatek Genio 510-EVK and 700-EVK boards, ssusb2 controller is
>> one but has two ports: one is routed to the M.2 slot, the other is on
>> the RPi header who does support full OTG.
>> Since Mediatek Genio 700-EVK USB support was added, dual role mode
>> property is set to otg for ssusb2. This config prevents the M.2
>> Wifi/Bluetooth module, present on those boards and exposing Bluetooth
>> as an USB device to be properly detected at startup, so configure for
>> the ssusb2 dr_mode property as host instead.
>>
>> Fixes: 1afaeca17238 ("arm64: dts: mediatek: mt8390-genio-700: Add USB, TypeC Controller, MUX")
>> Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>
>> ---
>> I've tested this patch on Mediatek Genio 510-EVK board with a kernel
>> based on linux-next (tag: next-20250331).
>> ---
>>   arch/arm64/boot/dts/mediatek/mt8390-genio-common.dtsi | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/boot/dts/mediatek/mt8390-genio-common.dtsi b/arch/arm64/boot/dts/mediatek/mt8390-genio-common.dtsi
>> index 60139e6dffd8e0e326690d922f3360d829ed026b..3a9d429f0f14b501ae41551dfe7272f242345138 100644
>> --- a/arch/arm64/boot/dts/mediatek/mt8390-genio-common.dtsi
>> +++ b/arch/arm64/boot/dts/mediatek/mt8390-genio-common.dtsi
>> @@ -1199,7 +1199,13 @@ xhci_ss_ep: endpoint {
>>   };
>>   
>>   &ssusb2 {
>> -	dr_mode = "otg";
>> +	/*
>> +	 * the ssusb2 controller is one but we got two ports : one is routed
>> +	 * to the M.2 slot, the other is on the RPi header who does support
>> +	 * full OTG but we keep it disabled otherwise the BT on the M.2 slot
>> +	 * USB line goes obviously dead if switching to gadget mode.
>> +	 */
>> +	dr_mode = "host";
> 
> Hi,
> 
> while I agree with this change, now that this controller is fixed to host mode,
> the connector child node here which is supposed to probe with driver
> usb-conn-gpio, which would monitor the ID and VBUS lines and change the USB role
> as needed, will fail to probe with:
> 
>    platform 112a1000.usb:connector: deferred probe pending: usb-conn-gpio: failed to get role switch
> 
> as indeed there no longer is a role switch registered.
> 
> For that reason, I believe as part of this commit you should also disable the
> connector. Since role switching is no longer supported by this controller,
> there's no sense in even trying to probe this driver.
> 
> Thanks,
> Nícolas

Can we instead go for role-switch-default-mode = "host", with a big comment
in the devicetree saying that the controller is shared between BT and the other
port? :-)

Cheers,
Angelo