From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hiroshi Doyu <hdoyu-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCHv3 14/19] iommu/tegra: smmu: Get "nvidia,memory-clients"
	from DT
Date: Thu, 31 Oct 2013 09:18:08 +0100
Message-ID: <20131031.101808.1830527808656695540.hdoyu@nvidia.com>
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Cc: "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>, "rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org" <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>, "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" <iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, "grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
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Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> wrote @ Wed, 30 Oct 2013 23:44:04 +0100:

> > +	host1x {
> > +		compatible = "nvidia,tegra30-host1x", "simple-bus";
> > +		nvidia,memory-clients = <&smmu TEGRA_SWGROUP_HC>;
> > +		....
> > +		gr3d {
> > +			compatible = "nvidia,tegra30-gr3d";
> > +			nvidia,memory-clients = <&smmu TEGRA_SWGROUP_NV
> > +						       TEGRA_SWGROUP_NV2>;
> 
> Why one cell for the host1x property, and two cells for the gr3d
> property; shouldn't they be the same length?

That can vary. Even a single device node in DT can belong to multiple
software groups.

> > diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
> 
> > +static u64 smmu_of_get_memory_client(struct device *dev)
> 
> > +	np = of_parse_phandle(dev->of_node, propname, 0);
> > +	if (np != smmu_handle->dev->of_node)
> > +		return ~0;
> > +
> > +	prop = of_get_property(dev->of_node, propname, &bytes);
> > +	if (!prop || !bytes)
> > +		return ~0;
> 
> of_parse_phandle_with_fixed_args() might be a good fit here, or perhaps
> require a property #smmu-cells in the SMMU node, thus allowing the
> non-fixed-length of_parse_phandle_with_args() to be used here.

I once considered of_parse_phandle_with_args() but I couldn't use that
since "#smmu-cells" needed to be fixed in smmu node, not in client
node. In this case, the number of argument(number of swgroup IDs)
varies per client device.