Re: [RFC] [PATCH 3/7] usb: ehci-omap: omap: Add OMAP4 support

[Felipe Balbi <felipe.balbi@nokia.com>]

Hi,

On Fri, Aug 20, 2010 at 07:47:07AM +0200, ext Gadiyar, Anand wrote:
>The differences between OMAP3 and OMAP4 are:
>- The OMAP4 has a different set of clocks which do not exist on OMAP3.
>- The register bits for configuring port modes is different

is it a different ip core or just a modification of the previous ?

>For the clock handling:
>One approach: On OMAP3, have a set of dummy clocks corresponding to the
>per-port clocks on OMAP4. Then the driver wouldn't need to know which
>SoC it is running on.
>
>Another approach:
>Have a different glue layer driver for OMAP4.
>
>For the register bit differences, we do need to know which SoC we are
>running on to be able to use the correct register bits. For this,

isn't the ehci ip revision different ? Why don't you use that instead of 
cpu_is_omap* 

>One approach:
>At the very minimum, we need a set of clocks to be enabled to be able to
>read the UHH_REVISION register, and we could use that to figure out which
>bits we need to use.

exactly

>The other approach I can think of is to have platform data tell us (I'm
>guessing this is a bad idea).

yeah, that would be bad...

>What do you think?

another approach:

make ohci and ehci play well together have an omap3-specific and one 
omap4-specific MFD-like driver that will instantiate ehci and ohci 
platform_drivers and handle clock + locking to shared address space.

then you define a set of accessor functions for registers with different 
offset that act differently depending on revision of the ip core.

Does that work ?

-- 
balbi

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