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

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Message-ID: <13595839.WFkdpM5auQ@wuerfel>
Date:	Sun, 27 Apr 2014 20:17:48 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	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,
	pullip.cho@...sung.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 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.

	Arnd
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