linux-kernel - Re: [PATCHv3 3/4] iommu/tegra: smmu: Refrain from accessing to AHB

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Date:	Thu, 03 May 2012 11:48:25 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Hiroshi DOYU <hdoyu@...dia.com>
CC:	linux-tegra@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Joerg Roedel <joerg.roedel@....com>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 3/4] iommu/tegra: smmu: Refrain from accessing to AHB

On 05/03/2012 10:05 AM, Hiroshi DOYU wrote:
> Use "tegra_ahb_enable_smmu()" to inform AHB that SMMU is
> ready, instead of directly aceessing AHB registers.

You need to make the Kconfig option for the SMMU either depend on or
select the TEGRA_AHB option. If you don't, then if someone disables the
AHB driver, the SMMU driver may still build, yet fail to link since the
AHB API it calls doesn't exist.

> diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c

> @@ -398,10 +388,8 @@ static void smmu_setup_regs(struct smmu_device *smmu)
>  
>  	smmu_flush_regs(smmu, 1);
>  
> -	val = ahb_read(smmu, AHB_XBAR_CTRL);
> -	val |= AHB_XBAR_CTRL_SMMU_INIT_DONE_DONE <<
> -		AHB_XBAR_CTRL_SMMU_INIT_DONE_SHIFT;
> -	ahb_write(smmu, val, AHB_XBAR_CTRL);
> +	err = tegra_ahb_enable_smmu(smmu->ahb);
> +	return err;

You can just "return tegra_ahb_..." here.

> @@ -911,14 +899,16 @@ static int tegra_smmu_probe(struct platform_device *pdev)

> +	smmu->ahb = of_parse_phandle(pdev->dev.of_node, "ahb", 0);

Hmm, "ahb" should probably be "nvidia,ahb".

I see that neither this patch nor the next patch include binding
documentation that describe this property. Can you please add documentation.
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