From: Max Krummenacher <max.oss.09@gmail.com>
To: Max Krummenacher <max.oss.09@gmail.com>
Cc: Max Krummenacher <max.krummenacher@toradex.com>,
Lucas Stach <l.stach@pengutronix.de>,
linux-arm-kernel@lists.infradead.org,
Fabio Estevam <festevam@gmail.com>,
Rouven Czerwinski <r.czerwinski@pengutronix.de>,
linux-kernel@vger.kernel.org,
Ahmad Fatoum <a.fatoum@pengutronix.de>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Sascha Hauer <s.hauer@pengutronix.de>,
Russell King <linux@armlinux.org.uk>,
Shawn Guo <shawnguo@kernel.org>,
NXP Linux Team <linux-imx@nxp.com>
Subject: [PATCH 0/1] ARM: imx: build suspend-imx6.S with arm instruction set
Date: Mon, 11 Jan 2021 16:17:03 +0100 [thread overview]
Message-ID: <20210111151704.26296-1-max.krummenacher@toradex.com> (raw)
When the kernel is configured to use the Thumb-2 instruction set
"suspend-to-memory" fails to resume while in ARM mode it works as
expected.
(I used imx_v6_v7_defconfig and deselected ARCH_MULTI_V6 and selected
THUMB2_KERNEL)
The system prints what is expected when suspending but an event of a
wakeup source does give no output.
root@colibri-imx6ull:~# echo mem > /sys/power/state
[ 58.610809] PM: suspend entry (deep)
[ 58.629354] Filesystems sync: 0.014 seconds
[ 58.653411] Freezing user space processes ... (elapsed 0.001 seconds) done.
[ 58.661941] OOM killer disabled.
[ 58.665176] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
[ 58.674028] printk: Suspending console(s) (use no_console_suspend to debug)
-> trigger wakeup event, no reaction.
It looks like the CPU resumes unconditionally in ARM instruction mode
and then chokes on the presented Thumb-2 code it should execute on resume.
With the following code change resume succeeds.
--- a/arch/arm/mach-imx/suspend-imx6.S
+++ b/arch/arm/mach-imx/suspend-imx6.S
@@ -287,11 +286,20 @@ rbc_loop:
bne rbc_loop
/* Zzz, enter stop mode */
wfi
+#ifdef CONFIG_THUMB2_KERNEL
+ /* i.MX CPUs seem to leave stop mode set to ARM instruction set */
+ .arm
+#endif
nop
nop
nop
nop
+#ifdef CONFIG_THUMB2_KERNEL
+ /* switch to Thumb2 mode */
+ sub pc, pc, #3
+ .thumb
+#endif
/*
I propose however to compile the whole file in ARM mode and have the
linker taking care of the ARM/Thumb-2 switching. This would also keep
the code working if a i.MX CPU variant exists that resumes in the same
mode in which it went to sleep.
Max Krummenacher (1):
ARM: imx: build suspend-imx6.S with arm instruction set
arch/arm/mach-imx/suspend-imx6.S | 1 +
1 file changed, 1 insertion(+)
--
2.26.2
next reply other threads:[~2021-01-11 15:18 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 15:17 Max Krummenacher [this message]
2021-01-11 15:17 ` [PATCH 1/1] ARM: imx: build suspend-imx6.S with arm instruction set Max Krummenacher
2021-01-11 17:38 ` Oleksandr Suvorov
2021-01-11 17:49 ` Ahmad Fatoum
2021-01-11 18:30 ` Max Krummenacher
2021-01-18 6:45 ` Shawn Guo
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