Re: [PATCH] Lock 7 is cpuidle specific, use non-generic value for locking

From: Lina Iyer
Date: Thu Mar 12 2015 - 16:49:16 EST

On Thu, Mar 12 2015 at 14:35 -0600, Stephen Boyd wrote:
On 03/12/15 12:38, Lina Iyer wrote:

sign off?

:) I was just hacking it to make it easier to understand. Sure.

drivers/hwspinlock/qcom_hwspinlock.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/hwspinlock/qcom_hwspinlock.c b/drivers/hwspinlock/qcom_hwspinlock.c
index 93b62e0..7642524 100644
--- a/drivers/hwspinlock/qcom_hwspinlock.c
+++ b/drivers/hwspinlock/qcom_hwspinlock.c
@@ -25,16 +25,23 @@

#include "hwspinlock_internal.h"


static int qcom_hwspinlock_trylock(struct hwspinlock *lock)
struct regmap_field *field = lock->priv;
u32 lock_owner;
int ret;
+ u32 proc_id;

- ret = regmap_field_write(field, QCOM_MUTEX_APPS_PROC_ID);
+ proc_id = hwspin_lock_get_id(lock) == QCOM_CPUIDLE_LOCK ?
+ QCOM_MUTEX_CPUIDLE_OFFSET + smp_processor_id():

So we assume that the caller will always be the CPU that is locking the
lock? Also, do we assume that the remote side knows our CPU scheme here?
smp_processor_id() returns the logical CPU and not the physical CPU
number so hopefully the remote side doesn't care about logical CPU
numbers being written to the lock value.

The remote side (SCM) doesnt care the value written. We use 128+cpu to
be unique in Linux(128 is to make sure it doesnt clash with predefined
values used across by other processors.

Perhaps it would be better to have a way to tell the hwspinlock
framework what value we want written to the lock value.

That would be good, if there is value in that for other platforms, I
will gladly make the change.


+ ret = regmap_field_write(field, proc_id);
if (ret)
return ret;

@@ -42,7 +49,7 @@ static int qcom_hwspinlock_trylock(struct hwspinlock *lock)
if (ret)
return ret;

- return lock_owner == QCOM_MUTEX_APPS_PROC_ID;
+ return lock_owner == proc_id;

static void qcom_hwspinlock_unlock(struct hwspinlock *lock)

The unlock path checks proc_id so we need to update the path there too.

Good point. I missed it.

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