[PATCH v3 00/17] NVMe PCI endpoint target driver

[Rick Wertenbroek]

Hello,
I have tested the NVMe endpoint function extensively on two extra
platforms to run on, the FriendlyElec CM3588+NAS Kit [1] and NanoPC T6
[2] (with PCIe x1, x2, and x4 links).

Besides testing with Linux based hosts (Ubuntu 20.04, 23.10, 24.04), I
also tested that the NVMe device is recognized by a Windows 10
Enterprise host and can be formatted and used as a regular disk. I
also tested on MacOS Monterey on a Macbook Pro 2016 (Intel based) host
through a M.2 to USB-C adapter [3], the drive is recognized and
usable.

The USB-C adapter is based on the ASM2464PD chipset [4] which does
USB4/Thunderbolt to PCIe/NVMe, I tested with PCI over Thunderbolt with
the MacOS host, so the host sees the NVMe endpoint function directly
as a PCI device and the NVMe drive is seen as such. This works well.

The only test case that did not work is when I tested the ASM2464PD
chipset NVMe to regular USB functionality, where the chipset is the
host, and presents itself to the PC as a "usb-storage" class device,
but this didn't work because the ASM2464PD never enabled the NVMe
controller (CC.EN bit in BAR0), the PCI Link between the ASM2464PD and
endpoint function gets up however, and to the host PC the USB device
is recognized ("usb-storage" class, like a USB stick, e.g., /dev/sda),
but it cannot be read (shows as 0B block device). As I cannot debug
the chipset itself I don't know why the NVMe endpoint doesn't get
enabled. This might very well be a quirk in the ASM2464PD chipset and
is a very specific use case so I don't think it indicates any major
issues with the endpoint function, but I report it here for the sake
of completion.

I have tested with different storage backend devices for actual
storage (USB, eMMC, and NVMe (PCIe x1, x2) on the NAS kit).

In summary, over PCI the endpoint function works well with all three
Linux/MacOS/Windows hosts.

Tested-by: Rick Wertenbroek <rick.wertenbroek at gmail.com>
(I don't know if this applies as I co-developed the endpoint function
with Damien)

Best regards,
Rick

[1] https://wiki.friendlyelec.com/wiki/index.php/CM3588
[2] https://wiki.friendlyelec.com/wiki/index.php/NanoPC-T6
[3] https://www.aliexpress.com/item/1005006316029054.html
[4] https://www.asmedia.com.tw/product/802zX91Yw3tsFgm4/C64ZX59yu4sY1GW5/ASM2464PD