Re: [PATCH 0/3] ARM: dts: bcm2711-rpi-cm4-io: Enable xHCI host

[Florian Fainelli <florian.fainelli@broadcom.com>]

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On 11/27/23 11:22, Stefan Wahren wrote:
> Hi,
> 
> Am 27.11.23 um 19:41 schrieb Florian Fainelli:
>> On 11/27/23 09:44, Justin Chen wrote:
>>>
>>>
>>> On 11/27/23 8:28 AM, Phil Elwell wrote:
>>>> On Mon, 27 Nov 2023 at 12:39, Stefan Wahren <wahrenst@gmx.net> wrote:
>>>>>
>>>>> Hi Phil,
>>>>>
>>>>>>>>> Hi Justin,
>>>>>>>>>
>>>>>>>>> [add Phil]
>>>>>>>>>
>>>>>>>>> Am 27.11.23 um 07:02 schrieb Justin Chen:
>>>>>>>>>> On 11/25/23 6:56 PM, Stefan Wahren wrote:
>>>>>>>>>>> In contrast to the Raspberry Pi 4, the Compute Module 4 or
>>>>>>>>>>> the IO board
>>>>>>>>>>> does not have a VL805 USB 3.0 host controller, which is
>>>>>>>>>>> connected via
>>>>>>>>>>> PCIe. Instead, the BCM2711 on the Compute Module provides the
>>>>>>>>>>> built-in
>>>>>>>>>>> xHCI.
>>>>>>>>>>>
>>>>>>>>>> Does this work? I maintain this built-in xHCI controller
>>>>>>>>>> internally. I
>>>>>>>>>> wasn't aware the Compute Module uses this block.
>>>>>>>>> i successful tested this with a CM4 (arm 32 bit,
>>>>>>>>> multi_v7_lpae_defconfig) with eMMC. Before this series the USB
>>>>>>>>> devices
>>>>>>>>> (mouse, keyboard) connected to the host interface didn't work.
>>>>>>>>> After
>>>>>>>>> comparing vendor DTS with mainline i noticed the missing xHCI
>>>>>>>>> block [1].
>>>>>>>>> Unfortunately i wasn't able to get further information from the
>>>>>>>>> public
>>>>>>>>> datasheets. I don't know if the VideoCore does some magic
>>>>>>>>> tricks on the
>>>>>>>>> xHCI or i missed some downstream xHCI changes.
>>>>>>>>>
>>>>>>>>>> This block is held in reset and needs a bit toggled to get things
>>>>>>>>>> going. Florian, just to confirm, this is our
>>>>>>>>>> "brcm,xhci-brcm-v2" block
>>>>>>>>>> correct?
>>>>>>>>>>
>>>>>>>>>> Justin
>>>>>>>>> [1]  -
>>>>>>>>> https://github.com/raspberrypi/linux/blob/rpi-6.1.y/arch/arm/boot/dts/bcm2711-rpi-ds.dtsi#L119
>>>>>>>>>
>>>>>>>> What's the question here? Does the XHCI block present in the
>>>>>>>> raspberrypi/linux dtsi file really exist? Yes it does.
>>>>>>> since i don't have any documentation about the xHCI block, i
>>>>>>> assumed the
>>>>>>> compatible generic-xhci is correct. But Justin seems to suggest
>>>>>>> that the
>>>>>>> xHCI block needs some special treatment and we need a specific
>>>>>>> compatible.
>>>>>>>
>>>>>>> Did i missed some xHCI driver changes?
>>>>>>> Does the VC firmware something to the xHCI especially on CM4?
>>>>>> The firmware switches the on-board USB pins from DWC-OTG to XHCI if
>>>>>> otg_mode=1 is set in config.txt, or if booting over USB MSD.
>>>>> is this pinctrl/pinmux available from ARM via 0x7e200000 or a
>>>>> different
>>>>> IO address?
>>>>
>>>> It's in a different, undocumented block.
>>>>
>>>> Phil
>>>
>>> Well if it works, then maybe I am misunderstanding something here.
>>> Maybe its time for me to pick up a CM4 board.
>> There is one on my desk that you are welcome to use, or remote into if
>> you prefer.
>>
>> To answer your earlier question, yes this is the same block as the one
>> present in 72112 for which we use the "brcm,xhci-brcm-v2" compatible
>> string, it would be preferable to have it backed by that compatible
>> string in case we happen to support suspend/resume on the Pi 4B one
>> day, if nothing else.
>>
>> I did confirm that after applying Stefan's patches plus changing my
>> config.txt to have otg_mode=1, USB continues to be fully functional.
>> This is the case with using both "generic-xhci" or "brcm,xhci-brcm-v2"
>> so with the minor request to update the compatible to
>> "brcm,xhci-brcm-v2", this is:
>>
>> Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
>>
>> Stefan, I am getting a deadlock on boot if I leave your changes in and
>> uncomment dwc_otg=1 in config.txt, is there an alias or something that
>> the boot loader should be patching?
> 
> sorry but i'm unable reproduce those deadlocks, neither in arm or arm64,
> with eMMC or without eMMC, xhci builtin or module. If i uncomment this
> in config.txt, USB host is just disabled.

Here is my config.txt FWIW:

# A bit too verbose
uart_2ndstage=1
enable_uart=1
arm_64bit=1
# Custom kernel images
kernel=kernel8-upstream.img
#kernel=kernel7l.img
#device_tree=bcm2711-rpi-4-b-UPSTREAM.dtb
device_tree=bcm2711-rpi-cm4-io-UPSTREAM.dtb
force_turbo=1
# DWC-OTG <=> XHCI
#otg_mode=1

> 
> I'm using the following firmware:
> 
> raspberrypi-firmware soc:firmware: Attached to firmware from
> 2023-03-17T10:50:39

OK, my CM4 is at 2022-07-25T15:10:17, updating to 2023-10-17T15:39:16 
does not really show any difference.

> 
> Is this DTS difference a problem?

It does not appear so, changing the node unit-name does not affect the 
results.

> 
> upstream   -> xhci: usb@7e9c0000
> downstream -> xhci: xhci@7e9c0000

Side question: does the VPU boot ROM or firmware take care of 
configuring the USB PHY somehow? Should not we also have a Device Tree 
node for it eventually?
-- 
Florian


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