Re: [PATCH RFC v2 0/2] hwspinlock: Introduce raw capability for hwspinlock_device

[Lina Iyer]

On Fri, Aug 14 2015 at 04:52 -0600, Ohad Ben-Cohen wrote:
> On Thu, Aug 13, 2015 at 6:25 PM, Andy Gross <agross@xxxxxxxxxxxxxx> wrote:
> > The issue in hardwiring this into the driver itself means forfeiting
> > extensibility.  So on one side (w/ raw support), we get the ability to deal with
> > the lock number changing.  On the other side (w/o raw), we'd have to probably
> > tie this to chip compat to figure out which lock is the 'special' if it ever
> > changes.
>
> It sounds like the decision "which lock to use" is a separate problem
> from "can it go raw".
Absolutely.

> If the hardware doesn't prohibit raw mode, then every lock can be used
> in raw mode. So you just have to pick one and make sure both sides
> know which lock you use --- which is a classic multi-processor
> synchronization issue.
>
> > It's arbitrary right now.  The remote processor selected a number, not the
> > processor running Linux.
>
> Is the number hardcoded right now? and you're using
> hwspin_lock_request_specific on the Linux side to acquire the lock?
Yes, the number is hardcoded in the SPM power controller driver. It
explicitly requests Lock #7

-- Lina
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