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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>
47 lines
1.3 KiB
ArmAsm
47 lines
1.3 KiB
ArmAsm
/*
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* Shared SCU setup for mach-shmobile
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*
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* Copyright (C) 2012 Bastian Hecht
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR /PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/linkage.h>
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#include <linux/init.h>
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#include <asm/memory.h>
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/*
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* Boot code for secondary CPUs.
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*
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* First we turn on L1 cache coherency for our CPU. Then we jump to
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* secondary_startup that invalidates the cache and hands over control
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* to the common ARM startup code.
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*/
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ENTRY(shmobile_boot_scu)
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@ r0 = SCU base address
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mrc p15, 0, r1, c0, c0, 5 @ read MIPDR
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and r1, r1, #3 @ mask out cpu ID
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lsl r1, r1, #3 @ we will shift by cpu_id * 8 bits
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ldr r2, [r0, #8] @ SCU Power Status Register
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mov r3, #3
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lsl r3, r3, r1
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bic r2, r2, r3 @ Clear bits of our CPU (Run Mode)
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str r2, [r0, #8] @ write back
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b secondary_startup
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ENDPROC(shmobile_boot_scu)
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.text
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.align 2
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.globl shmobile_scu_base
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shmobile_scu_base:
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.space 4
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