From: Max Krummenacher <max.oss.09@gmail.com>
To: Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc: Rouven Czerwinski <r.czerwinski@pengutronix.de>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Shawn Guo <shawnguo@kernel.org>,
Sascha Hauer <s.hauer@pengutronix.de>,
linux-kernel@vger.kernel.org,
Russell King <linux@armlinux.org.uk>,
NXP Linux Team <linux-imx@nxp.com>,
Max Krummenacher <max.krummenacher@toradex.com>,
Fabio Estevam <festevam@gmail.com>,
linux-arm-kernel@lists.infradead.org,
Lucas Stach <l.stach@pengutronix.de>
Subject: Re: [PATCH 1/1] ARM: imx: build suspend-imx6.S with arm instruction set
Date: Mon, 11 Jan 2021 19:30:51 +0100 [thread overview]
Message-ID: <147692b37063057ce4128894db112caf9320b65b.camel@gmail.com> (raw)
In-Reply-To: <ecc65820-6b94-bb11-f475-aa0296fce5b8@pengutronix.de>
Resent due to gmail adding HTML, sorry for the noise.
Am Montag, den 11.01.2021, 18:49 +0100 schrieb
Ahmad Fatoum:
>
> On 11.01.21 16:17, Max Krummenacher wrote:
> > When the kernel is configured to use the Thumb-2 instruction set
> > "suspend-to-memory" fails to resume. Observed on a Colibri iMX6ULL
> > (i.MX 6ULL) and Apalis iMX6 (i.MX 6Q).
> >
> > It looks like the CPU resumes unconditionally in ARM instruction mode
> > and then chokes on the presented Thumb-2 code it should execute.
> >
> > Fix this by using the arm instruction set for all code in
> > suspend-imx6.S.
> >
> > Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
> >
> > ---
> >
> > arch/arm/mach-imx/suspend-imx6.S | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm/mach-imx/suspend-imx6.S b/arch/arm/mach-imx/suspend-imx6.S
> > index 1eabf2d2834be..e06f946b75b96 100644
> > --- a/arch/arm/mach-imx/suspend-imx6.S
> > +++ b/arch/arm/mach-imx/suspend-imx6.S
> > @@ -67,6 +67,7 @@
> > #define MX6Q_CCM_CCR 0x0
> >
> > .align 3
> > + .arm
>
> You had a return to thumb at the end of this subroutine in the cover letter,
> yet here it's omitted. Why?
Now the whole subroutine is compiled for ARM and the return address has bit
0 set so that on jumping back to the caller the CPU will switch back to
Thumb-2.
Probably the return to Thumb-2 isn't needed in the cover letter solution
and it would also work to finish the subroutine in ARM instruction set.
However it looks strange to me if a function which begins with the ARM
instruction set would come to the return in Thumb-2.
>
> >
> > .macro sync_l2_cache
> >
> >
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next prev parent reply other threads:[~2021-01-11 18:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 15:17 [PATCH 0/1] ARM: imx: build suspend-imx6.S with arm instruction set Max Krummenacher
2021-01-11 15:17 ` [PATCH 1/1] " Max Krummenacher
2021-01-11 17:38 ` Oleksandr Suvorov
2021-01-11 17:49 ` Ahmad Fatoum
2021-01-11 18:30 ` Max Krummenacher [this message]
2021-01-18 6:45 ` Shawn Guo
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