Re: [PATCH] i2c: pasemi: Add IRQ support for Apple Silicon

[Christian Zigotzky]

On 23 August 2022 at 03:50 am, Michael Ellerman wrote:
> Arminder Singh <arminders208@xxxxxxxxxxx> writes:
> > This is the first time I'm interacting with the Linux mailing lists, so
> > please don't eviscerate me *too much* if I get the formatting wrong.
> > Of course I'm always willing to take criticism and improve my formatting
> > in the future.
> >
> > This patch adds support for IRQs to the PASemi I2C controller driver.
> > This will allow for faster performing I2C transactions on Apple Silicon
> > hardware, as previously, the driver was forced to poll the SMSTA register
> > for a set amount of time.
> >
> > With this patchset the driver on Apple silicon hardware will instead wait
> > for an interrupt which will signal the completion of the I2C transaction.
> > The timeout value for this completion will be the same as the current
> > amount of time the I2C driver polls for.
> >
> > This will result in some performance improvement since the driver will be
> > waiting for less time than it does right now on Apple Silicon hardware.
> >
> > The patch right now will only enable IRQs for Apple Silicon I2C chips,
> > and only if it's able to successfully request the IRQ from the kernel.
> >
> > === Testing ===
> >
> > This patch has been tested on both the mainline Linux kernel tree and
> > the Asahi branch (https://github.com/AsahiLinux/linux.git) on both an
> > M1 and M2 MacBook Air, and it compiles successfully as both a module and
> > built-in to the kernel itself. The patch in both trees successfully boots
> > to userspace without any hitch.
> >
> > I do not have PASemi hardware on hand unfortunately, so I'm unable to test
> > the impact of this patch on old PASemi hardware. This is also why I've
> > elected to do the IRQ request and enablement on the Apple platform driver
> > and not in the common file, as I'm not sure if PASemi hardware supports
> > IRQs.
> I've added Darren and Christian to Cc, they have helped with PASemi
> development and testing in the past, and may be able to help test this
> series on PASemi hardware.
>
> cheers

Tested-by: Christian Zigotzky <chzigotzky at xenosoft.de>

on an A-EON AmigaOne X1000 with a PASemi PWRficient PA6T-1682 processor.