[PATCH master v2] ARM: i.MX7: enable caches when booted over USB

Ahmad Fatoum a.fatoum at pengutronix.de
Sun Oct 9 23:34:30 PDT 2022

BootROM on the i.MX7 doesn't set the SMP bit when booted
over serial download. This leads to vastly worse performance
when doing memory-heavy operations in a USB-booted system,
as the caches are not utilized. Example running md5sum over
a 25M image in ramfs:

  without patch: 10796ms
  with    patch: 457ms

This issue isn't unique to the i.MX7, but exists for the i.MX6UL as
well, which also has the Cortex-A7 as CPU. Like with
imx6ul_cpu_lowlevel_init(), adapt imx7_cpu_lowlevel_init() to avoid this
slow down.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
Signed-off-by: Johannes Zink <j.zink at pengutronix.de>
v1 -> v2:
  - don't drop arm arm_cpu_lowlevel_init as cortex_a7_lowlevel_init
    does not call it (Marco)
 arch/arm/mach-imx/cpu_init.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/mach-imx/cpu_init.c b/arch/arm/mach-imx/cpu_init.c
index ea3621541979..3f16ca70ce26 100644
--- a/arch/arm/mach-imx/cpu_init.c
+++ b/arch/arm/mach-imx/cpu_init.c
@@ -49,6 +49,7 @@ void imx6ul_cpu_lowlevel_init(void)
 void imx7_cpu_lowlevel_init(void)
+	cortex_a7_lowlevel_init();

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