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

Lina Iyer
2015-08-14T13:52:15Z

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@codeaurora.org> 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