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Date:   Mon, 23 Mar 2020 00:09:51 +0100
From:   Clemens Gruber <clemens.gruber@pqgruber.com>
To:     Sasha Levin <sashal@kernel.org>
Cc:     Ahmad Fatoum <a.fatoum@pengutronix.de>, festevam@gmail.com,
        s.hauer@pengutronix.de, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org, linux-imx@nxp.com, kernel@pengutronix.de,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rouven Czerwinski <r.czerwinski@pengutronix.de>,
        shawnguo@kernel.org, linux-arm-kernel@lists.infradead.org,
        Lucas Stach <l.stach@pengutronix.de>,
        Clemens Gruber <clemens.gruber@pqgruber.com>
Subject: Re: [PATCH] ARM: imx: build v7_cpu_resume() unconditionally
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 <20200322185022.GA82867@workstation.tuxnet>
 <20200322202224.GQ4189@sasha-vm>
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On Sun, Mar 22, 2020 at 04:22:24PM -0400, Sasha Levin wrote:
> On Sun, Mar 22, 2020 at 07:50:22PM +0100, Clemens Gruber wrote:
> > Hi,
> > 
> > On Thu, Jan 16, 2020 at 03:18:49PM +0100, Rouven Czerwinski wrote:
> > > From: Ahmad Fatoum <a.fatoum@pengutronix.de>
> > > 
> > > This function is not only needed by the platform suspend code, but is also
> > > reused as the CPU resume function when the ARM cores can be powered down
> > > completely in deep idle, which is the case on i.MX6SX and i.MX6UL(L).
> > > 
> > > Providing the static inline stub whenever CONFIG_SUSPEND is disabled means
> > > that those platforms will hang on resume from cpuidle if suspend is disabled.
> > > 
> > > So there are two problems:
> > > 
> > >   - The static inline stub masks the linker error
> > >   - The function is not available where needed
> > > 
> > > Fix both by just building the function unconditionally, when
> > > CONFIG_SOC_IMX6 is enabled. The actual code is three instructions long,
> > > so it's arguably ok to just leave it in for all i.MX6 kernel configurations.
> > > 
> > > Fixes: 05136f0897b5 ("ARM: imx: support arm power off in cpuidle for i.mx6sx")
> > > Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> > > Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> > > Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
> > > ---
> > >  arch/arm/mach-imx/Makefile       |  2 ++
> > >  arch/arm/mach-imx/common.h       |  4 ++--
> > >  arch/arm/mach-imx/resume-imx6.S  | 24 ++++++++++++++++++++++++
> > >  arch/arm/mach-imx/suspend-imx6.S | 14 --------------
> > >  4 files changed, 28 insertions(+), 16 deletions(-)
> > >  create mode 100644 arch/arm/mach-imx/resume-imx6.S
> > > 
> > > diff --git a/arch/arm/mach-imx/Makefile b/arch/arm/mach-imx/Makefile
> > > index 35ff620537e6..03506ce46149 100644
> > > --- a/arch/arm/mach-imx/Makefile
> > > +++ b/arch/arm/mach-imx/Makefile
> > > @@ -91,6 +91,8 @@ AFLAGS_suspend-imx6.o :=-Wa,-march=armv7-a
> > >  obj-$(CONFIG_SOC_IMX6) += suspend-imx6.o
> > >  obj-$(CONFIG_SOC_IMX53) += suspend-imx53.o
> > >  endif
> > > +AFLAGS_resume-imx6.o :=-Wa,-march=armv7-a
> > > +obj-$(CONFIG_SOC_IMX6) += resume-imx6.o
> > >  obj-$(CONFIG_SOC_IMX6) += pm-imx6.o
> > > 
> > >  obj-$(CONFIG_SOC_IMX1) += mach-imx1.o
> > > diff --git a/arch/arm/mach-imx/common.h b/arch/arm/mach-imx/common.h
> > > index 912aeceb4ff8..5aa5796cff0e 100644
> > > --- a/arch/arm/mach-imx/common.h
> > > +++ b/arch/arm/mach-imx/common.h
> > > @@ -109,17 +109,17 @@ void imx_cpu_die(unsigned int cpu);
> > >  int imx_cpu_kill(unsigned int cpu);
> > > 
> > >  #ifdef CONFIG_SUSPEND
> > > -void v7_cpu_resume(void);
> > >  void imx53_suspend(void __iomem *ocram_vbase);
> > >  extern const u32 imx53_suspend_sz;
> > >  void imx6_suspend(void __iomem *ocram_vbase);
> > >  #else
> > > -static inline void v7_cpu_resume(void) {}
> > >  static inline void imx53_suspend(void __iomem *ocram_vbase) {}
> > >  static const u32 imx53_suspend_sz;
> > >  static inline void imx6_suspend(void __iomem *ocram_vbase) {}
> > >  #endif
> > > 
> > > +void v7_cpu_resume(void);
> > > +
> > >  void imx6_pm_ccm_init(const char *ccm_compat);
> > >  void imx6q_pm_init(void);
> > >  void imx6dl_pm_init(void);
> > > diff --git a/arch/arm/mach-imx/resume-imx6.S b/arch/arm/mach-imx/resume-imx6.S
> > > new file mode 100644
> > > index 000000000000..5bd1ba7ef15b
> > > --- /dev/null
> > > +++ b/arch/arm/mach-imx/resume-imx6.S
> > > @@ -0,0 +1,24 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > > +/*
> > > + * Copyright 2014 Freescale Semiconductor, Inc.
> > > + */
> > > +
> > > +#include <linux/linkage.h>
> > > +#include <asm/assembler.h>
> > > +#include <asm/asm-offsets.h>
> > > +#include <asm/hardware/cache-l2x0.h>
> > > +#include "hardware.h"
> > > +
> > > +/*
> > > + * The following code must assume it is running from physical address
> > > + * where absolute virtual addresses to the data section have to be
> > > + * turned into relative ones.
> > > + */
> > > +
> > > +ENTRY(v7_cpu_resume)
> > > +	bl	v7_invalidate_l1
> > > +#ifdef CONFIG_CACHE_L2X0
> > > +	bl	l2c310_early_resume
> > > +#endif
> > > +	b	cpu_resume
> > > +ENDPROC(v7_cpu_resume)
> > > diff --git a/arch/arm/mach-imx/suspend-imx6.S b/arch/arm/mach-imx/suspend-imx6.S
> > > index 062391ff13da..1eabf2d2834b 100644
> > > --- a/arch/arm/mach-imx/suspend-imx6.S
> > > +++ b/arch/arm/mach-imx/suspend-imx6.S
> > > @@ -327,17 +327,3 @@ resume:
> > > 
> > >  	ret	lr
> > >  ENDPROC(imx6_suspend)
> > > -
> > > -/*
> > > - * The following code must assume it is running from physical address
> > > - * where absolute virtual addresses to the data section have to be
> > > - * turned into relative ones.
> > > - */
> > > -
> > > -ENTRY(v7_cpu_resume)
> > > -	bl	v7_invalidate_l1
> > > -#ifdef CONFIG_CACHE_L2X0
> > > -	bl	l2c310_early_resume
> > > -#endif
> > > -	b	cpu_resume
> > > -ENDPROC(v7_cpu_resume)
> > > --
> > > 2.25.0
> > 
> > This patch broke the build for our i.MX6 kernel.
> > 
> > I am referring to commits 512a928aff in mainline and
> > 7199cb65bb in linux-stable.
> > 
> > In our kernel, neither CONFIG_PM nor CONFIG_SUSPEND are set. Therefore,
> > ARM_CPU_SUSPEND is also unset, which means that sleep.S (containing
> > cpu_resume) is not built.
> > 
> > With this patch, ld reports the following error:
> > arch/arm/mach-imx/resume-imx6.o: in function `v7_cpu_resume':
> > (.text+0x8): undefined reference to `cpu_resume'
> 
> Is this a problem with Linus's tree as well?

Yes, it affects Linus's tree and linux-stable.

Reverting 512a928aff in mainline (7199cb65bb in linux-stable) fixes the
build error for us.

Thanks,
Clemens