linux-kernel - Re: [PATCH v3] hwspinlock/msm: Add support for Qualcomm MSM HW Mutex block

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Date:	Thu, 27 Feb 2014 21:52:43 -0800
From:	Bjorn Andersson <bjorn@...o.se>
To:	Kumar Gala <galak@...eaurora.org>
Cc:	Ohad Ben-Cohen <ohad@...ery.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ian.campbell@...rix.com>,
	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	Jeffrey Hugo <jhugo@...eaurora.org>,
	Eric Holmberg <eholmber@...eaurora.org>
Subject: Re: [PATCH v3] hwspinlock/msm: Add support for Qualcomm MSM HW Mutex block

Hi Kumar,

I pulled this in to my 3.14 tree and gave it a spin. But I keep
hitting the case of unlock below telling me that someone else is
holding the lock.

On Wed, Aug 14, 2013 at 12:09 PM, Kumar Gala <galak@...eaurora.org> wrote:
[...]
> +
> +static int msm_hwspinlock_trylock(struct hwspinlock *lock)
> +{
> +       void __iomem *lock_addr = lock->priv;
> +
> +       writel_relaxed(SPINLOCK_ID_APPS_PROC, lock_addr);

You need some sort of barrier here; the caf code have a smp_mb() here,
inserting that solves the problem.

> +
> +       return readl_relaxed(lock_addr) == SPINLOCK_ID_APPS_PROC;
> +}
> +
> +static void msm_hwspinlock_unlock(struct hwspinlock *lock)
> +{
> +       u32 lock_owner;
> +       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 us (actual owner is %d)\n",
> +                               __func__, lock_owner);
> +       }
> +
> +       writel_relaxed(0, lock_addr);
> +}
> +

Part of this I think this driver looks good, it would be nice to get
the last details cleaned up so we could get it into the tree.

Regards,
Bjorn
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