[RFC] Multi queue support in ethernet/freescale/ucc_geth.c

[Li Yang-R58472]

> -----Original Message-----
> From: Paul Gortmaker [mailto:paul.gortmaker at windriver.com]
> Sent: Friday, February 03, 2012 6:42 AM
> To: Li Yang-R58472
> Cc: netdev at vger.kernel.org; linuxppc-dev at lists.ozlabs.org
> Subject: [RFC] Multi queue support in ethernet/freescale/ucc_geth.c
> 
> Hi Li,

Hi Paul,

Sorry for the late response due to holidays.

> 
> A while back DaveM mentioned that it would be good to break out the ring
> allocations[1] in this driver.
> 
> I was looking at it, and in the process noticed this:
> 
> $ grep 'numQueues.*=' drivers/net/ethernet/freescale/ucc_geth.c
>         .numQueuesTx = 1,
>         .numQueuesRx = 1,
> $
> 
> My interpretation of the above is that there is no way (aside from a code
> edit) to enable multi queue support.
> They are only ever assigned one time, to a value of one.
> 
> Assuming I'm not missing something obvious, is the multi queue support
> functional and tested, or just old code that never got tested and
> subsequently enabled?

Previously the device is only used on single core cpu, so we didn't have the incentive to enable multi-queue.  It is not tested on Linux currently.

> 
> The reason I ask, is that the ring allocation code gets rid of the loop
> wrapping it, if the driver is really only meant to ever have just single
> queues for Rx/Tx. And other areas of the driver can also be simplified
> accordingly as well.

Well.  I would prefer the other way which is to add the multi-queue support as we are using the QE in multi-core SoC and the current driver is having almost all the code needed for multi-queue except interface to the protocol layer.

- Leo