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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 14 Jan 2020 11:59:36 +0100
Message-ID: <CAK8P3a3x55A8y9kR34zy8YyRhto8uay7PZGbDAufupiNS3+ihA@mail.gmail.com>
Subject: Re: [PATCH] soc: imx: Makefile: only build soc-imx8 when CONFIG_ARM64
To:     Peng Fan <peng.fan@nxp.com>
Cc:     =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>, Abel Vesa <abel.vesa@nxp.com>,
        Anson Huang <anson.huang@nxp.com>,
        "festevam@gmail.com" <festevam@gmail.com>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        Leonard Crestez <leonard.crestez@nxp.com>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>
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On Tue, Jan 14, 2020 at 9:32 AM Peng Fan <peng.fan@nxp.com> wrote:
> > Subject: Re: [PATCH] soc: imx: Makefile: only build soc-imx8 when
> > CONFIG_ARM64
> >
> > On Tue, Jan 14, 2020 at 08:08:45AM +0000, Peng Fan wrote:
> > > From: Peng Fan <peng.fan@nxp.com>
> > >
> > > Only need to build soc-imx8.c when CONFIG_ARM64 defined, no need to
> > > build it for CONFIG_ARM32 currently.
> > >
> > > Signed-off-by: Peng Fan <peng.fan@nxp.com>
> > > ---
> > >  drivers/soc/imx/Makefile | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/soc/imx/Makefile b/drivers/soc/imx/Makefile index
> > > cf9ca42ff739..cfcbc62b11d7 100644
> > > --- a/drivers/soc/imx/Makefile
> > > +++ b/drivers/soc/imx/Makefile
> > > @@ -1,5 +1,7 @@
> > >  # SPDX-License-Identifier: GPL-2.0-only
> > >  obj-$(CONFIG_HAVE_IMX_GPC) += gpc.o
> > >  obj-$(CONFIG_IMX_GPCV2_PM_DOMAINS) += gpcv2.o
> > > +ifdef CONFIG_ARM64
> > >  obj-$(CONFIG_ARCH_MXC) += soc-imx8.o
> > > +endif
> >
> > For earlier SoCs we had kconfig symbols like SOC_IMX25. Actually
> > SOC_IMX8 would be the right one to decide about soc-imx8.c to be compiled,
> > it would be easier to read and verify than the suggested
> > "ARM64 && ARCH_MXC" and it would stay right once NXP presents it's next
> > 64-bit SoC i.MX9.
>
> There is no SOC_IMX8 currently. Need to introduce one in
> arch/arm64/Kconfig.platforms. But I not see other vendors
> introduce options like SOC_XX. Is this the right direction to
> add one in Kconfig.platforms?

I think it would be more consistent with the other platforms to have
a symbol in drivers/soc/imx/Kconfig to control whether we build
that driver.

If the driver is well written, it should be possible to allow compile
testing it on any architecture (please test this, at least on x86).

For some SoCs, we also allow running 32-bit kernels, so it would
not be wrong to allow enabling the symbol on 32-bit ARM as
well, but this is probably something where you want to consider
the bigger picture to see if you want to support that configuration
or not.

      Arnd