Re: [PATCH v2] hwspinlock/msm: Add support for Qualcomm MSM HW Mutexblock

[Jeffrey Hugo]

On 8/12/2013 10:35 AM, Stephen Boyd wrote:
> On 07/29/13 15:00, Kumar Gala wrote:
> > diff --git a/drivers/hwspinlock/msm_hwspinlock.c b/drivers/hwspinlock/msm_hwspinlock.c
> > new file mode 100644
> > index 0000000..dbd9a69
> > --- /dev/null
> > +++ b/drivers/hwspinlock/msm_hwspinlock.c
> > @@ -0,0 +1,150 @@
> > +/*
> > + * Copyright (c) 2013, The Linux Foundation. All rights reserved.
> > + *
> > + * This software is licensed under the terms of the GNU General Public
> > + * License version 2, as published by the Free Software Foundation, and
> > + * may be copied, distributed, and modified under those terms.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/kernel.h>
> > +#include <linux/slab.h>
> > +#include <linux/device.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/of.h>
> > +#include <linux/of_address.h>
> > +#include <linux/of_device.h>
> > +#include <linux/hwspinlock.h>
> > +#include <linux/io.h>
> > +
> > +#include "hwspinlock_internal.h"
> > +
> > +#define SPINLOCK_ID_APPS_PROC	1
>
> Is this id only for the apps processor? What about hexagon? Does it need
> a different number?

Yes, hexagon would need a different id based on what job that particular 
hexagon processor is doing.  I'm not currently aware of a hexagon 
usecase, but I believe modifying the DT binding in the future would 
cover the usecase if it comes up.

> > +#define BASE_ID			0
> > +
> > +static int msm_hwspinlock_trylock(struct hwspinlock *lock)
> > +{
> > +	void __iomem *lock_addr = lock->priv;
> > +
> > +	writel_relaxed(SPINLOCK_ID_APPS_PROC, lock_addr);
> > +	smp_mb();
> > +	return readl_relaxed(lock_addr) == SPINLOCK_ID_APPS_PROC;
> > +}
> > +
> > +static void msm_hwspinlock_unlock(struct hwspinlock *lock)
> > +{
> > +	int lock_owner;
>
> This should probably be u32 to be explicit about the size of the register.
>
> > +	void __iomem *lock_addr = lock->priv;
> > +
> > +	lock_owner = readl_relaxed(lock_addr);
> > +	if (lock_owner != SPINLOCK_ID_APPS_PROC) {
> > +		pr_err("%s: spinlock not owned by Apps (actual owner is %d)\n",
>
> Maybe you should just say "spinlock not owned by us (actual owner is
> %d)" so that this driver is agnostic to the processor it runs on?
>
> > +				__func__, lock_owner);
> > +	}
> > +
> > +	writel_relaxed(0, lock_addr);
> > +	smp_mb();
> > +}


Jeffrey Hugo
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