[U-Boot] [RFC PATCH v2 0/6] Port of MUSB driver from Linux

[Tom Rini]

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On 09/21/12 17:55, Marek Vasut wrote:
> Dear Ilya Yanok,
> 
>> Current MUSB driver in U-Boot uses old UDC API while new gagdet 
>> client drivers need new gadget API. Also current MUSB driver has 
>> some significant limitations (like inability to handle tx for 
>> endpoints other than ep0). So I think port of new Linux driver
>> is desirable.
>> 
>> This is initial port, performed mostly by putting DM and OTG code
>> under #ifndef __UBOOT__ clauses. My intention was to be as close
>> as possible to the original to ease of possible resyncs. Some
>> warnings are suppressed via CFLAGS. There are some style problems
>> but I'm not touching them for now for the above mentioned reason.
>> There is obviously some room for optimisation, some structure
>> fields are unused as well as (probably) some code.
>> 
>> This is not a replacement for existing MUSB driver (at least for 
>> now), cause there are still consumers of the old interface and 
>> the only ported backend is for TI AM335X (while the old code has
>>  a bunch of other backends).
>> 
>> OTG and DMA are not supported. The only ported driver is for TI 
>> AM33xx, but others should be easy to port too.
>> 
>> Virtual root hub is not implemented but this shouldn't be a big 
>> problem as the old code has virtual root hub support enabled only
>> for Blackfin platform.
>> 
>> Tested it on AM335x EVM and BeagleBone with CDC Ethernet gadget 
>> and a bunch of storage devices.
>> 
>> Pathes are rather big because of the original code size (and I 
>> didn't delete unused code, just disabled it). So it's probably 
>> better to look at changes as compared to Linux code. I prepared 
>> such version also, you can find it at [1]. Hopefully it will be 
>> also useful if resync with the kernel will be needed in future.
>> 
>> [1] https://github.com/yanok/u-boot/tree/musb-changes-from-linux
>> 
> [...]
> 
> I'm glad about this. But how can we make this work if we already 
> have a driver for this in u-boot, now we will have another. Tom ?

Part of our pain point here is that, if I'm following everything
right, we're switching from our home-grown MUSB framework to the
kernel one.  The good thing is that there's not many users of the
existing framework.  Being able to switch to a codebase we can re-sync
with the kernel for is a good thing.  It comes down to how much of an
effort it is to convert and leave untested the other platforms.  The
good news I believe is that aside from am335x everything else already
has a kernel portion to work from.

- -- 
Tom
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