Re: [RFC 0/2] i2c-designware: Add support for AMD PSP semaphore

Jan Dąbroś
2021-12-27T07:00:22Z

sob., 25 gru 2021 o 16:59 Andy Shevchenko <andy.shevchenko@gmail.com>
napisał(a):
>
> On Thu, Dec 23, 2021 at 4:43 PM Jan Dabros <jsd@semihalf.com> wrote:
> >
> > This patchset comprises support for new i2c-designware controller setup on some
> > AMD Cezanne SoCs, where x86 is sharing i2c bus with PSP. PSP uses the same
> > controller and acts as an i2c arbitrator there (x86 is leasing bus from it).
> >
> > First commit aims to improve generic i2c-designware code by adding extra locking
> > on probe() and disable() paths. I would like to ask someone with access to
> > boards which use Intel BayTrail(CONFIG_I2C_DESIGNWARE_BAYTRAIL) to verify
> > behavior of my changes on such setup.
> >
> > Second commit adds support for new PSP semaphore arbitration mechanism.
> > Implementation is similar to the one from i2c-designware-baytrail.c however
> > there are two main differences:
> > 1) Add new ACPI ID in order to protect against silent binding of the old driver
> > to the setup with PSP semaphore. Extra flag ARBITRATION_SEMAPHORE added to this
> > new _HID allows to recognize setup with PSP.
> > 2) Beside acquire_lock() and release_lock() methods we are also applying quirks
> > to the lock_bus() and unlock_bus() global adapter methods. With this in place
> > all i2c clients drivers may lock i2c bus for a desired number of i2c
> > transactions (e.g. write-wait-read) without being aware of that such bus is
> > shared with another entity.
> >
> > Mark this patchset as RFC, since waiting for new ACPI ID value. As a temporary
> > measure use "AMDI9999". Once proper one will be ready, will re-send this CL for
> > review & merge.
> >
> > Looking forward to some feedback.
>
> When you will be ready, CC a new version also to Hans, he may look at
> it from the Baytrail functionality perspective.

Thanks for the hint, it will be very helpful to have this tested on
Baytrail. From other comments on this RFC it seems that I would need
to affect Baytrail-semaphore path even more than initially thought.

Best Regards,
Jan