[PATCH v2 1/3] spi: implemented driver for Cirrus EP93xx SPI controller

[Mika Westerberg]

On Thu, Apr 01, 2010 at 01:15:20AM +0100, Martin Guy wrote:
> On 3/25/10, Mika Westerberg <mika.westerberg at iki.fi> wrote:
> >  > > This patch adds an SPI master driver for the Cirrus EP93xx SPI controller found
> >  > >  in EP93xx chips (EP9301, EP9302, EP9307, EP9312 and EP9315).
> >  > >
> >  > >  Driver currently supports only interrupt driven mode but in future we may add
> >  > >  polling mode support as well.
> 
> I've been staring more at this again and it looks (2 clock
> strangenesses and extensive control reg setting apart) like good code.

Thanks :)

> I have another question: like the Cirrus driver, this takes 100% CPU
> doing busy wait for the current transfer to complete.

Well it sleeps in ep93xx_spi_process_transfer() while current
transfer is complete. It shouldn't busy wait. At least that was not
my intention. If you have lot of data to transfer (for example while
using mmc_spi), the driver will be very busy.

But I can take a look on this and see if there is something wrong.

> Given that this driver is interrupt-based, is there any reason why it
> can't do something else in the meanwhile?

I had an idea that the driver could keep SPI controller interrupts
enabled and start next transfer in interrupt handler but I didn't
implement that yet, because first I wanted a driver that works.

> Not that that's a reason not to include it in 2.6.35 - it works well
> and we can think whether to make it more efficient in N+1...

Yeah, maybe we can optimize that later.

Thank you very much. It is good to hear that someone (else than me)
has been using this :)

Regards,
MW