[PATCH 7/8] usb: eth: Bind ASIX AX88179A/AX88772D/AX88279 to CDC ECM/NCM driver

[Marek Vasut]

On 7/12/26 12:14 PM, Jonas Karlman wrote:

Hello Jonas,

>> On 7/11/26 6:08 PM, Jonas Karlman wrote:
>>> The ASIX AX88179A, AX88772D and AX88279 USB Ethernet controller
>>> revisions has both CDC ECM and CDC NCM support.
>>>
>>>     AX88179:  0b95:1790 1.00
>>>     AX88179A: 0b95:1790 2.00
>>>     AX88772D: 0b95:1790 3.00
>>>     AX88279:  0b95:1790 4.00
>>>
>>> Prefer using the CDC NCM or CDC ECM driver for the 2.00-4.00 version
>>> range of the 0b95:1790 ASIX USB Ethernet controllers.
>>
>> Why this specific range ?
> 
> Sorry, my commit message was not clear enough. Only the last three
> entries listed above have ECM/NCM support stated in their datasheet.
> 
> The version seems to correlate with the different "generation" of the
> AX88179/AX88772 controllers.
> 
> The initial AX88179/AX88772 revisions, tagged with version 1.00, does
> not state support for ECM/NCM in the datasheet. And all my dongles are
> tagged with version 2.00 or above, i.e. using AX88179A or a later
> revision or version in the family.
> 
> The version matching also seems to match revision handling in vendor
> driver [1], so that suggest that these assumptions are correct. Based on
> [1] it looks like version 5.00 for AX88279A was added recently.
> 
> [1] https://github.com/mmoya/asix-usb-nic-linux-driver/blob/main/ax_main.c#L2913-L2939

OK

>> [...]
>>
>>> +++ b/drivers/usb/eth/asix88179.c
>>> @@ -691,7 +691,12 @@ U_BOOT_DRIVER(ax88179_eth) = {
>>>    };
>>>    
>>>    static const struct usb_device_id ax88179_eth_id_table[] = {
>>> +#if IS_ENABLED(CONFIG_USB_ETHER_CDC_ECM) || IS_ENABLED(CONFIG_USB_ETHER_CDC_NCM)
>>
>> This is USB, this should be auto-detected without any need for ifdeffery.
> 
> As stated in the cover letter, U-Boot only support driver detection of the
> first (cfgno=0) configuration.
> 
>    U-Boot currently only has support for automatic binding of the first
>    device configuration for devices, so this implementaion works by adding
>    bindings for VID/PID pairs and letting the drivers try to change active
>    configuration during probe.
> 
> To work around this limitation, the VID/PID pair is added here.
> 
> U-Boot USB core structs only have support for carrying information about
> a single configuration, so the cfgno=0 is set as active configuration
> and USB driver matches only on information of this first config.
> 
> Initially I tried to add limited support for at least parsing all
> configuration descriptors and make usb command list all possible configs.
> 
> However, there are other parts that only where saved during config desc
> parsing and where then overwritten by parsing of next config descriptor.
> 
> Next hack was to just force setting the cfgno that matched NCM, and that
> made USB driver matching the new NCM driver, but this was not scalable.
> 
> So to not having to re-work how USB core store config and handles driver
> matching, the cleanest way was to export the set config helper and use
> VID/PID matching in these drivers.
> 
> Hopefully someone can add proper support for driver matching based on
> all possible device configurations in the future. Not something I plan
> to address, I just wanted my USB Ethernet dongles to work :-)

Try and look at 575c68279c41 ("usb: kbd: support Apple Magic Keyboards 
(2021)") , maybe that can help with some handling of second interface 
descriptor ?

>>> +	{ USB_DEVICE_VER(0x0b95, 0x1790, 0, 0x0100),
>>> +		.driver_info = FLAG_TYPE_AX88179 },
>>> +#else
>>>    	{ USB_DEVICE(0x0b95, 0x1790), .driver_info = FLAG_TYPE_AX88179 },
>>> +#endif
>>>    	{ USB_DEVICE(0x0b95, 0x178a), .driver_info = FLAG_TYPE_AX88178a },
>> [...]
>>
>> I recall there was some USB URB size limit on this ASIX USB MAC, was
>> that ever sorted out ?
> 
> Correct, the ax88179_eth driver is currently requesting a bigger RX
> buffer than what the MAC seem to be able to handle when EHCI controller
> is used.
> 
> Trying to get a workaround that limited the size to 16 KiB, similar to
> what Linux uses, was partially rejected.
> 
> This ultimately made me to look closer at NCM/ECM and the implementation
> of these drivers. And for U-Boot purpose using NCM/ECM mode seems more
> logical than continue trying to use the undocumented vendor magic :-)
> 
> For ECM only a single packet is sent, so a 2 KiB buffer is used. And for
> NCM it defaults to 16 KiB and also uses the information provided from
> the descriptors to keep the the used buffer size within device limits.
> 
> To conclude, using ECM/NCM mode resolved all issues I had related to USB
> URB size and this ASIX USB MAC so I have now fully switched to just
> using ECM/NCM driver for the boards in my personal lab.
Can we fix the EHCI driver too ?

It feels like there is a bug, which is papered over by these patches.