From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
Subject: Re: [PATCH v2 11/22] iommu/tegra: smmu: Add Tegra 114 support
Date: Thu, 18 Jul 2013 14:01:36 -0600
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To: Hiroshi Doyu <hdoyu-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Cc: linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
List-Id: linux-tegra@vger.kernel.org

On 07/05/2013 04:44 AM, Hiroshi Doyu wrote:
> Tegra 114 SMMU uses the almost same logic as one in Tegra 30 except
> that they have different HaredWare Accelerators(HWA). Those difference
> is provided from DT.

> diff --git a/Documentation/devicetree/bindings/iommu/nvidia,tegra30-smmu.txt b/Documentation/devicetree/bindings/iommu/nvidia,tegra30-smmu.txt

>  Required properties:
> -- compatible : "nvidia,tegra30-smmu"
> +- compatible : "nvidia,tegra114-smmu", "nvidia,tegra30-smmu"

So that we don't have to list every single chip in that list, we've
often written that as:

compatible : "nvidia,tegra<chip>-smmu".

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

>  static struct of_device_id tegra_smmu_of_match[] = {
> +	{ .compatible = "nvidia,tegra114-smmu", },
>  	{ .compatible = "nvidia,tegra30-smmu", },

So, there are no HW differences, and hence no driver changes required?
In that case, there's no point making the driver explicitly support
nvidia,tegra114-smmu, since the DT will always be:

compatible = "nvidia,tegra114-smmu", "nvidia,tegra30-smmu";

... and hence always match on the existing nvidia,tegra30-smmu entry in
that table.