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

From: Lina Iyer
Date: Thu Mar 12 2015 - 15:32:00 EST

On Fri, Feb 27 2015 at 15:30 -0700, Bjorn Andersson wrote:
Add driver for Qualcomm Hardware Mutex block found in many Qualcomm

Based on initial effort by Kumar Gala <galak@xxxxxxxxxxxxxx>

Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxx>


+#include "hwspinlock_internal.h"
Hi Bjorn,

Not all locks use 1 to indicate its locked. For example lock index 7 is
used by cpuidle driver between HLOS and SCM. It uses a write value of
(128 + smp_processor_id()) to lock.

A cpu acquires the remote spin lock, and calls into SCM to terminate the
power down sequence while passing the state of the L2. The lock help
guarantee the last core to hold the spinlock to have the most up to date
value for the L2 flush flag.


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.


+ struct regmap_field *field = lock->priv;
+ u32 lock_owner;
+ int ret;
+ ret = regmap_field_write(field, QCOM_MUTEX_APPS_PROC_ID);
+ if (ret)
+ return ret;
+ ret = regmap_field_read(field, &lock_owner);
+ if (ret)
+ return ret;
+ return lock_owner == QCOM_MUTEX_APPS_PROC_ID;

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