linux-kernel - Re: [PATCH v11 13/27] iommu/exynos: support for device tree

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Date:	Wed, 19 Mar 2014 18:06:28 +0900
From:	Cho KyongHo <pullip.cho@...sung.com>
To:	Tomasz Figa <t.figa@...sung.com>
Cc:	Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	Linux DeviceTree <devicetree@...r.kernel.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	Grant Grundler <grundler@...omium.org>,
	Joerg Roedel <joro@...tes.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Prathyush <prathyush.k@...sung.com>,
	Rahul Sharma <rahul.sharma@...sung.com>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Varun Sethi <Varun.Sethi@...escale.com>
Subject: Re: [PATCH v11 13/27] iommu/exynos: support for device tree

On Tue, 18 Mar 2014 16:25:11 +0100, Tomasz Figa wrote:
> On 18.03.2014 11:52, Cho KyongHo wrote:
> > On Fri, 14 Mar 2014 14:39:33 +0100, Tomasz Figa wrote:
> >>> @@ -557,11 +558,23 @@ static int exynos_sysmmu_probe(struct platform_device *pdev)
> >>>    	return 0;
> >>>    }
> >>>
> >>> -static struct platform_driver exynos_sysmmu_driver = {
> >>> -	.probe		= exynos_sysmmu_probe,
> >>> -	.driver		= {
> >>> +#ifdef CONFIG_OF
> >>> +static struct of_device_id sysmmu_of_match[] __initconst = {
> >>> +	{ .compatible	= "samsung,sysmmu-v1", },
> >>> +	{ .compatible	= "samsung,sysmmu-v2", },
> >>> +	{ .compatible	= "samsung,sysmmu-v3.1", },
> >>> +	{ .compatible	= "samsung,sysmmu-v3.2", },
> >>> +	{ .compatible	= "samsung,sysmmu-v3.3", },
> >>
> >> Do you need all these compatible strings? I mean, are there any
> >> implementation differences that can't be identified by reading IP
> >> registers, such as REG_MMU_VERSION?
> >>
> >
> > Unfortunately, there is a SoC which overrides REG_MMU_VERSION with
> > a value for RTL designers and it is not related to System MMU
> > versions.
> 
> OK.
> 
> What about having a generic compatible string for Samsung SysMMU then, 
> but an additional property that can override the version to account for 
> such brokenness? If not provided, the version would be read from 
> REG_MMU_VERSION.
> 

Yes it is one of possible idea.
Let me think what better way is.

Thank you.

KyongHo
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