Re: [PATCH v2] USB: Add MSM USB Device Controller driver

[Pavan Kondeti <pkondeti@codeaurora.org>]

On 11/19/2010 10:46 PM, Matthieu CASTET wrote:
> Hi,
>
> Brian Swetland a écrit :
>> On Tue, Nov 9, 2010 at 6:54 PM, David Brownell <david-b@pacbell.net>
>> wrote:
>>>
>>> --- On Tue, 11/9/10, Pavan Kondeti <pkondeti@codeaurora.org> wrote:
>>>
>>>>>> Hi Matthieu,
>>>>>>
>>>>>>> This look like the arc/chipidea/mips ehci otg
>>>> core.
>>>>>> Yes. It is chipidea core for ARM.
>>>>>>> Why can't you reuse the ci13xxx_udc.c driver
>>> That basic approach is FAR PREFERABLE. Fix
>>> the bugs once, tune once, and so forth, reuse
>>> the ULPI support, etc. Work on more
>>> platforms, since the silicon IP is reused.
>>>
>>> You'll end up with more folk who can help
>>> maintain the driver too, since the pool of
>>> potential helpers won't be limited to those
>>> who have/use MSM hardware.
>>>
>>> Just be sure to cleanly factor the bus
>>> (PCI vs MSM-s ARM platform flavor and
>>> SoC glues (bus-related). That factoring
>>> will likely be the hardest part; but there
>>> are examples of similar stuff in Linux today.
>>
>> The main headache is that this particular IP has different bugs in
>> different instantiations (I know, for example, it exists in Tegra with
>> a different set of issues around fetching descriptor heads and cache
>> alignment, on MSM7201A after extensive testing we discovered there was
>> no reliable way of adding a descriptor to a list of transactions once
>> that queue was active, etc...), so things that work in one SoC may
>> break another, etc, etc, but that's part of the adventure I suppose.
>> I certainly agree that one unified driver is the way to go if you can
>> make it all work.
>>
> The best way to handle this is to introduce flags in the driver. For
> example look at drivers/mmc/host/sdhci.c (quirk flags).
>
> But for now, let's make work msm version. We can add workaround for
> other controller later.
>
I am working on separating PCI stuff from ci13xxx_udc driver and 
implementing specific hooks needed for MSM. I am relying on 
gadget_is_xxx() macro for MSM specific workarounds.

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