linux-kernel - Re: [PATCH v12 15/31] iommu/exynos: handle 'mmu-masters' property of DT and improve handling sysmmu

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Date:	Thu, 01 May 2014 23:08:56 +0900
From:	Cho KyongHo <pullip.cho@...sung.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Shaik Ameer Basha <shaik.ameer@...sung.com>,
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	kgene.kim@...sung.com, prathyush.k@...sung.com,
	grundler@...omium.org, joro@...tes.org,
	supash.ramaswamy@...aro.org, tomasz.figa@...il.com,
	joshi@...sung.com, sachin.kamat@...aro.org, s.nawrocki@...sung.com,
	Varun.Sethi@...escale.com, a.motakis@...tualopensystems.com,
	t.figa@...sung.com, rahul.sharma@...sung.com
Subject: Re: [PATCH v12 15/31] iommu/exynos: handle 'mmu-masters' property of
 DT and improve handling sysmmu

On Sun, 27 Apr 2014 20:17:48 +0200, Arnd Bergmann wrote:
> On Sunday 27 April 2014 13:07:47 Shaik Ameer Basha wrote:
> > @@ -542,14 +592,41 @@ static int __init exynos_sysmmu_probe(struct platform_device *pdev)
> >  		}
> >  	}
> >  
> > +	/* Relation between master and System MMU is 1:1. */
> > +	node = of_parse_phandle(dev->of_node, "mmu-masters", 0);
> > +	if (node) {
> > +		struct platform_device *master = of_find_device_by_node(node);
> > +
> > +		if (!master) {
> > +			dev_err(dev, "%s: mmu-master '%s' not found\n",
> > +				__func__, node->name);
> > +			return -EINVAL;
> > +		}
> > +
> > +		if (master->dev.archdata.iommu != NULL) {
> > +			dev_err(dev, "%s: '%s' is master of other MMU\n",
> > +				__func__, node->name);
> > +			return -EINVAL;
> > +		}
> > +
> > +		/*
> > +		 * archdata.iommu will be initialized with exynos_iommu_client
> > +		 * in sysmmu_hook_driver_register().
> > +		 */
> > +		master->dev.archdata.iommu = dev;
> > +	}
> 
> I think parsing of generic properties like this shouldn't be done
> by the individual driver. It belongs into core iommu code and should
> be done when the devices are probed.
> 
> > +
> > +static struct notifier_block sysmmu_notifier = {
> > +	.notifier_call = &sysmmu_hook_driver_register,
> > +};
> > +
> > +static int __init exynos_iommu_prepare(void)
> > +{
> > +	static bool registered = false;
> > +	int ret;
> > +
> > +	if (registered)
> > +		return 0;
> > +
> > +	ret = bus_register_notifier(&platform_bus_type, &sysmmu_notifier);
> > +	if (!ret)
> > +		registered = true;
> > +	else
> > +		pr_err("Failed to register sysmmu_notifier\n");
> > +
> > +	return ret;
> > +}
> 
> This also means we should not have notifiers. Put it into core code to
> make sure all IOMMUs are handled the same way.
> 

Ok.

Thank you for addressing that.
I am also very interested in the discussion about it in the different thread.

KyongHo
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