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

From: Lina Iyer
Date: Fri Aug 14 2015 - 09:52:19 EST

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

It sounds like the decision "which lock to use" is a separate problem
from "can it go raw".


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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