linux-kernel - Re: [PATCH v6 2/2] hwspinlock: qcom: Add support for Qualcomm HW Mutex block

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Date:	Wed, 18 Mar 2015 14:59:48 -0700
From:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
To:	Lina Iyer <lina.iyer@...aro.org>
CC:	Ohad Ben-Cohen <ohad@...ery.com>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	Jeffrey Hugo <jhugo@...eaurora.org>,
	Suman Anna <s-anna@...com>, Andy Gross <agross@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 2/2] hwspinlock: qcom: Add support for Qualcomm HW
 Mutex block

On Wed 18 Mar 09:45 PDT 2015, Lina Iyer wrote:

> On Wed, Mar 18 2015 at 09:56 -0600, Bjorn Andersson wrote:
> >On Thu 12 Mar 12:31 PDT 2015, Lina Iyer wrote:
> >
> >> On Fri, Feb 27 2015 at 15:30 -0700, Bjorn Andersson wrote:
[..]
> >> >+#define QCOM_MUTEX_NUM_LOCKS	32
> >>
> >> Also, talking to Jeff it seems like that out of the 32 locks defined
> >> only 8 is accessible from Linux. So its unnecessary and probably
> >> incorrect to assume that there are 32 locks available.
> >>
> >
> >The hardware block have 32 locks and the decision regarding which locks
> >this particular Linux system is allowed to access is configuration.
> >
> Understood. But while the hardware may support it, it may be right for
> Linux to be allowed to configure, giving a false sense of number of
> locks.
> 

You're not just randomly allocating these locks, the "sense of number of
locks" is most likely carried in an Excel sheet within Qualcomm.

Obviously the number 8 is arbitrary and a change of it is a question of
"system configuration" and not a matter of changing the implementation
of this device driver.

Regards,
Bjorn
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