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Date:   Mon, 28 Sep 2020 09:29:55 +0200
From:   Thierry Reding <thierry.reding@gmail.com>
To:     Dmitry Osipenko <digetx@gmail.com>
Cc:     Nicolin Chen <nicoleotsuka@gmail.com>, joro@8bytes.org,
        krzk@kernel.org, linux-tegra@vger.kernel.org,
        linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
        jonathanh@nvidia.com
Subject: Re: [PATCH 3/5] iommu/tegra-smmu: Use iommu_fwspec in
 .probe_/.attach_device()
Message-ID: <20200928072955.GE2837573@ulmo>
References: <20200926080719.6822-1-nicoleotsuka@gmail.com>
 <20200926080719.6822-4-nicoleotsuka@gmail.com>
 <ccb95c4e-64ba-bab9-1f75-0c6d287540b0@gmail.com>
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On Sat, Sep 26, 2020 at 05:48:17PM +0300, Dmitry Osipenko wrote:
> 26.09.2020 11:07, Nicolin Chen =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
> ...
> > +	/* NULL smmu pointer means that SMMU driver is not probed yet */
> > +	if (unlikely(!smmu))
> > +		return ERR_PTR(-EPROBE_DEFER);
>=20
> Hello, Nicolin!
>=20
> Please don't pollute code with likely/unlikely. This is not a
> performance-critical code.
>=20
> ...
> > -static struct platform_driver tegra_mc_driver =3D {
> > +struct platform_driver tegra_mc_driver =3D {
> >  	.driver =3D {
> >  		.name =3D "tegra-mc",
> >  		.of_match_table =3D tegra_mc_of_match,
> > diff --git a/include/soc/tegra/mc.h b/include/soc/tegra/mc.h
> > index 1238e35653d1..49a4cf64c4b9 100644
> > --- a/include/soc/tegra/mc.h
> > +++ b/include/soc/tegra/mc.h
> > @@ -184,4 +184,6 @@ struct tegra_mc {
> >  int tegra_mc_write_emem_configuration(struct tegra_mc *mc, unsigned lo=
ng rate);
> >  unsigned int tegra_mc_get_emem_device_count(struct tegra_mc *mc);
> > =20
> > +extern struct platform_driver tegra_mc_driver;
>=20
> No global variables, please. See for the example:
>=20
> https://elixir.bootlin.com/linux/v5.9-rc6/source/drivers/devfreq/tegra20-=
devfreq.c#L100
>=20
> The tegra_get_memory_controller() is now needed by multiple Tegra
> drivers, I think it should be good to have it added into the MC driver
> and then make it globally available for all drivers by making use of
> of_find_matching_node_and_match().
>=20
> diff --git a/drivers/memory/tegra/mc.c b/drivers/memory/tegra/mc.c
> index e1db209fd2ea..ed1bd6d00aaf 100644
> --- a/drivers/memory/tegra/mc.c
> +++ b/drivers/memory/tegra/mc.c
> @@ -43,6 +43,29 @@ static const struct of_device_id tegra_mc_of_match[] =
=3D {
>  };
>  MODULE_DEVICE_TABLE(of, tegra_mc_of_match);
>=20
> +struct tegra_mc *tegra_get_memory_controller(void)
> +{
> +	struct platform_device *pdev;
> +	struct device_node *np;
> +	struct tegra_mc *mc;
> +
> +	np =3D of_find_matching_node_and_match(NULL, tegra_mc_of_match, NULL);
> +	if (!np)
> +		return ERR_PTR(-ENOENT);
> +
> +	pdev =3D of_find_device_by_node(np);
> +	of_node_put(np);
> +	if (!pdev)
> +		return ERR_PTR(-ENODEV);
> +
> +	mc =3D platform_get_drvdata(pdev);
> +	if (!mc)
> +		return ERR_PTR(-EPROBE_DEFER);
> +
> +	return mc;
> +}
> +EXPORT_SYMBOL_GPL(tegra_get_memory_controller);

We already have tegra_smmu_find(), which should be enough for this
particular use-case.

Thierry

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