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

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Date:	Thu, 12 Mar 2015 13:35:21 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Lina Iyer <lina.iyer@...aro.org>, bjorn.andersson@...ymobile.com
CC:	linux-arm-msm@...r.kernel.org, jhugo@...eaurora.org,
	agross@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Lock 7 is cpuidle specific, use non-generic value for
 locking

On 03/12/15 12:38, Lina Iyer wrote:
> ---

sign off?

>  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"
>  
> -#define QCOM_MUTEX_APPS_PROC_ID	1
> -#define QCOM_MUTEX_NUM_LOCKS	32
> +#define QCOM_MUTEX_APPS_PROC_ID		1
> +#define QCOM_MUTEX_CPUIDLE_OFFSET	128
> +#define QCOM_CPUIDLE_LOCK		7
> +#define QCOM_MUTEX_NUM_LOCKS		32
>  
>  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.

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

> +			QCOM_MUTEX_APPS_PROC_ID;
> +
> +	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.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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