linux-kernel - RE: [PATCH] soc: imx: Makefile: only build soc-imx8 when CONFIG

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Date:   Wed, 15 Jan 2020 02:38:35 +0000
From:   Peng Fan <peng.fan@....com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Abel Vesa <abel.vesa@....com>,
        Anson Huang <anson.huang@....com>,
        "festevam@...il.com" <festevam@...il.com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        Leonard Crestez <leonard.crestez@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH] soc: imx: Makefile: only build soc-imx8 when CONFIG_ARM64

Hi Arnd,

> Subject: Re: [PATCH] soc: imx: Makefile: only build soc-imx8 when
> CONFIG_ARM64
> 
> On Tue, Jan 14, 2020 at 9:32 AM Peng Fan <peng.fan@....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@....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@....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.

Ok, I'll add Kconfig entry in drivers/soc/imx/Kconfig for various i.MX SoCs.

> 
> 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).

Yes.

> 
> 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.

Does the current upstream kernel support 32bit kernels on ARM64 platforms
without vendor specific stuff. I recalled that several years ago, NXP people
tried to upstream 32bit kernel support, but rejected by you.

So Is there any plan to support 32bit kernel on AARCH64 in upstream kernel?
Or any suggestions?

Thanks,
Peng.

> 
>       Arnd