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

[Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>]

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@xxxxxxx> 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@xxxxxxxxxxxx>
> >
> > 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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