ARM: v7 setup function should invalidate L1 cache

All ARMv5 and older CPUs invalidate their caches in the early assembly
setup function, prior to enabling the MMU.  This is because the L1
cache should not contain any data relevant to the execution of the
kernel at this point; all data should have been flushed out to memory.

This requirement should also be true for ARMv6 and ARMv7 CPUs - indeed,
these typically do not search their caches when caching is disabled (as
it needs to be when the MMU is disabled) so this change should be safe.

ARMv7 allows there to be CPUs which search their caches while caching is
disabled, and it's permitted that the cache is uninitialised at boot;
for these, the architecture reference manual requires that an
implementation specific code sequence is used immediately after reset
to ensure that the cache is placed into a sane state.  Such
functionality is definitely outside the remit of the Linux kernel, and
must be done by the SoC's firmware before _any_ CPU gets to the Linux
kernel.

Changing the data cache clean+invalidate to a mere invalidate allows us
to get rid of a lot of platform specific hacks around this issue for
their secondary CPU bringup paths - some of which were buggy.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Tested-by: Wei Xu <xuwei5@hisilicon.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

4 files changed, 3 insertions, 11 deletions

diff --git a/arch/arm/mach-shmobile/common.h b/arch/arm/mach-shmobile/common.h
index afc60bad6fd6..476092b86c6e 100644
--- a/arch/arm/mach-shmobile/common.h
+++ b/arch/arm/mach-shmobile/common.h
@@ -14,7 +14,6 @@ extern void shmobile_smp_sleep(void);
 extern void shmobile_smp_hook(unsigned int cpu, unsigned long fn,
 			      unsigned long arg);
 extern int shmobile_smp_cpu_disable(unsigned int cpu);
-extern void shmobile_invalidate_start(void);
 extern void shmobile_boot_scu(void);
 extern void shmobile_smp_scu_prepare_cpus(unsigned int max_cpus);
 extern void shmobile_smp_scu_cpu_die(unsigned int cpu);
diff --git a/arch/arm/mach-shmobile/headsmp-scu.S b/arch/arm/mach-shmobile/headsmp-scu.S
index 69df8bfac167..fa5248c52399 100644
--- a/arch/arm/mach-shmobile/headsmp-scu.S
+++ b/arch/arm/mach-shmobile/headsmp-scu.S
@@ -22,7 +22,7 @@
  * Boot code for secondary CPUs.
  *
  * First we turn on L1 cache coherency for our CPU. Then we jump to
- * shmobile_invalidate_start that invalidates the cache and hands over control
+ * secondary_startup that invalidates the cache and hands over control
  * to the common ARM startup code.
  */
 ENTRY(shmobile_boot_scu)
@@ -36,7 +36,7 @@ ENTRY(shmobile_boot_scu)
 	bic	r2, r2, r3		@ Clear bits of our CPU (Run Mode)
 	str	r2, [r0, #8]		@ write back
 
-	b	shmobile_invalidate_start
+	b	secondary_startup
 ENDPROC(shmobile_boot_scu)
 
 	.text
diff --git a/arch/arm/mach-shmobile/headsmp.S b/arch/arm/mach-shmobile/headsmp.S
index 50c491567e11..330c1fc63197 100644
--- a/arch/arm/mach-shmobile/headsmp.S
+++ b/arch/arm/mach-shmobile/headsmp.S
@@ -16,13 +16,6 @@
 #include <asm/assembler.h>
 #include <asm/memory.h>
 
-#ifdef CONFIG_SMP
-ENTRY(shmobile_invalidate_start)
-	bl	v7_invalidate_l1
-	b	secondary_startup
-ENDPROC(shmobile_invalidate_start)
-#endif
-
 /*
  * Reset vector for secondary CPUs.
  * This will be mapped at address 0 by SBAR register.
diff --git a/arch/arm/mach-shmobile/platsmp-apmu.c b/arch/arm/mach-shmobile/platsmp-apmu.c
index f483b560b066..b0790fc32282 100644
--- a/arch/arm/mach-shmobile/platsmp-apmu.c
+++ b/arch/arm/mach-shmobile/platsmp-apmu.c
@@ -133,7 +133,7 @@ void __init shmobile_smp_apmu_prepare_cpus(unsigned int max_cpus,
 int shmobile_smp_apmu_boot_secondary(unsigned int cpu, struct task_struct *idle)
 {
 	/* For this particular CPU register boot vector */
-	shmobile_smp_hook(cpu, virt_to_phys(shmobile_invalidate_start), 0);
+	shmobile_smp_hook(cpu, virt_to_phys(secondary_startup), 0);
 
 	return apmu_wrap(cpu, apmu_power_on);
 }