[Intel-gfx] [RFC 1/4] x86/platform/intel/iosf_mbi: Add a mutex for punit access

[Jarkko Nikula]

On 01/13/2017 12:51 PM, Ville Syrjälä wrote:
> On Fri, Jan 13, 2017 at 12:34:54PM +0200, Jarkko Nikula wrote:
>> On 01/13/2017 11:26 AM, Ville Syrjälä wrote:
>>> It also feels quite hand wavy since the punit could do whatever at
>>> any time AFAIK. Eg. if there's some thermal event or something the
>>> punit might kick into action. So trying to protect this from the OS
>>> side might not be able to avoid these problems entirely. It feels like
>>> there really should be some kind of shared hardware/firmware mutex
>>> with the punit to arbitrate access to the i2c bus.
>>>
>> There is an HW semaphore for I2C access. It is implemented in
>> drivers/i2c/busses/i2c-designware-baytrail.c and another set from Hans
>> is adding support for Cherrytrail into it.
>
> Then why do we need anything else?
>
 From this patch: "The punit on baytrail / cherrytrail systems is not 
only accessed through the iosf_mbi functions, but also by the i915 code."

-- 
Jarkko