linux-kernel - Re: [PATCH 0/3] Configure usb0 as peripheral on am335x boards

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Message-ID: <73a4545a-e149-261a-a0c5-a526e8740bd5@kernel.org>
Date:   Mon, 3 Jul 2023 18:27:47 +0300
From:   Roger Quadros <rogerq@...nel.org>
To:     Julien Panis <jpanis@...libre.com>,
        Tony Lindgren <tony@...mide.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-omap@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        vigneshr@...com, nm@...com, Tom Rini <trini@...sulko.com>
Subject: Re: [PATCH 0/3] Configure usb0 as peripheral on am335x boards



On 03/07/2023 17:14, Julien Panis wrote:
> On 7/3/23 15:44, Roger Quadros wrote:
>>
>> On 03/07/2023 14:56, Julien Panis wrote:
>>> On 6/30/23 21:40, Roger Quadros wrote:
>>>> Hi,
>>>>
>>>> On 30/06/2023 11:30, Julien Panis wrote:
>>>>> Hello Tony,
>>>>>
>>>>> On 6/30/23 09:20, Tony Lindgren wrote:
>>>>>> Hi,
>>>>>>
>>>>>> * Julien Panis <jpanis@...libre.com> [230629 13:10]:
>>>>>>> This series configures usb0 dr_mode as 'peripheral' for am335x-evm,
>>>>>>> am335x-evmsk, and am335x-icev2. This USB port is mainly used for
>>>>>>> RNDIS and DFU.
>>>>>> Is this a mini-B connector? Just wondering if it was originally attempted
>>>>>> to be configured as OTG or how it ended up with a host configuration..
>>>>> It's a micro USB-AB connector.
>>>>> I don't know how it ended up with a host configuration, it looks like an oversight.
>>>>> Maybe Vignesh or Nishanth can confirm (?)
>>>> usb0 role should be "otg".
>>>> It is rightly so in Linux DT. am33xx.dtsi contains "otg" and all AM335x board files inherit from it.
>>>>
>>>> So I don't think setting it to "peripheral" in u-boot is the right thing to do.
>>> This series is for kernel (not for u-boot).
>>> Why is it a problem to set usb0 as 'peripheral' in kernel for the 3 board dts ?
>>>
>>> With usb0 not set as 'peripheral', the 3 boards (am335x-evm, evm-sk, icev2)
>>> do not boot with uboot 2023.04. This error is returned, with LOG_LEVEL=5:
>>>      No USB device found
>>>      USB ether init failed
>>>      initcall sequence 8ffdbba4 failed at call 808024d9 (err=-19)
>>>      ### ERROR ### Please RESET the board ###
>>> This error is also returned with usb0 as 'otg'.
>> This error is at u-boot correct? This will need further investigation.
>>
>> Does it function correctly in Linux when kept as 'otg'?
>>
> 
> This error is at u-boot level, indeed. I add Tom Rini to this thread, since he
> was involved in the discussion here:
> https://lore.kernel.org/all/20230621-fix_usb_ether_init-v2-0-ff121f0e8d7a@baylibre.com/
> If dr_mode is set as 'peripheral' in '<board>-u-boot.dtsi' and kept as 'otg'
> in linux, it functions correctly in linux.

OK.

So NAK for this patch series as we don't want to break 'otg' on Linux.

u-boot doesn't support 'otg' mode. So we need to force it either to
'peripheral' or 'host'.

One solution would be to have 'peripheral' in am335x-*-u-boot.dts?

-- 
cheers,
-roger