* Felipe Balbi [off-list ref] [130528 09:42]:

Hi,

On Mon, May 27, 2013 at 05:02:09PM +0200, Arnd Bergmann wrote:

quoted

Hi Felipe,

We've gone through remaining work items for getting the ARM kernel
to full multiplatform support again, and MUSB came up. I'm sure you
have your own thoughts on this, but I'd like to know if there is
already a plan in place.

From what I can see, the driver in PIO mode should almost work
on multiple platforms, but there are a couple of compile-time
dependencies in it that need to be turned into run-time conditionals.
In particular the TUSB version seem sufficiently different that
it needs some extra work to be a true run-time option.

yeah, TUSB layer is quite messy, all the others should be doable though.

TUSB we can make depend on ARMv7, the only implementation we have
is for omap2420, which is ARMv6. This should solve the issue for
ARMv7 multiplatform builds for now.
 

quoted

The DMA support as far as I can tell has never been intended to
be usable in a multiplatform setup, but that also seems doable.

we're looking into dmaengine for that but will take a lot of work to
have something usable.

TUSB would work with dmaengine, but AFAIK we're still missing the
dmaengine configuration options to support increasing device end
FIFO address.
 

quoted

Looking just at the #ifdef statements in the driver, I found
that the following things need to be addressed:

* abstract musb_write_fifo and musb_read_fifo into callbacks
* move fifo_mode setting into glue driver for runtime selection

for the fifo mode, I'd rather detect the size of the internal fifo and
configure it dynamically based on that plus number of endpoints
configured in the IP.

quoted

* turn TUSB compile-time switches into run-time conditionals
* turn musb_ep_select into run-time switch
* make is_dma_capable/is_cppi_enabled/tusb_dma_omap run-time conditionals

those can be remove, actually. Back at Nokia we did a huge cleanup on
the DMA programming part, it can be very simple with no ifdefs at all,
just needs someone to put the work and test on all platforms.

quoted

* abtract dma_controller_create/destroy interface

Aside from this, a recent discussion with Maxime has brought up
that the Allwinner A1x platform (mach-sunxi) contains an MUSB variant
that is currently used with an independently implemented device driver,
see https://github.com/linux-sunxi/linux-sunxi/tree/sunxi-3.0/drivers/usb/sun5i_usb
I wonder if you have any insight on how that can be integrated into
musb, or whether it is likely to be a compatible version to start with.

just write a glue layer, should be as easy as that :-)

Yes the MUSB code should be able to support it considering the number
of implementations we already have there.

Regards,

Tony