6213f70e7c
Consolidating the "pen_release" stuff amongst the various SoC implementations gives credence to having a CPU holding pen for secondary CPUs. However, this is far from the truth. Many SoC implementations cargo-cult copied various bits of the pen release implementation from the initial Realview/Versatile Express implementation without understanding what it was or why it existed. The reason it existed is because these are _development_ platforms, and some board firmware is unable to individually control the startup of secondary CPUs. Moreover, they do not have a way to power down or reset secondary CPUs for hot-unplug. Hence, the pen_release implementation was designed for ARM Ltd's development platforms to provide a working implementation, even though it is very far from what is required. It was decided a while back to reduce the duplication by consolidating the "pen_release" variable, but this only made the situation worse - we have ended up with several implementations that read this variable but do not write it - again, showing the cargo-cult mentality at work, lack of proper review of new code, and in some cases a lack of testing. While it would be preferable to remove pen_release entirely from the kernel, this is not possible without help from the SoC maintainers, which seems to be lacking. However, I want to remove pen_release from arch code to remove the credence that having it gives. This patch removes pen_release from the arch code entirely, adding private per-SoC definitions for it instead, and explicitly stating that write_pen_release() is cargo-cult copied and should not be copied any further. Rename write_pen_release() in a similar fashion as well. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
104 lines
2.1 KiB
C
104 lines
2.1 KiB
C
/*
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* linux/arch/arm/mach-spear13xx/hotplug.c
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*
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* Copyright (C) 2012 ST Microelectronics Ltd.
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* Deepak Sikri <deepak.sikri@st.com>
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*
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* based upon linux/arch/arm/mach-realview/hotplug.c
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/smp.h>
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#include <asm/cp15.h>
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#include <asm/smp_plat.h>
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#include "generic.h"
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static inline void cpu_enter_lowpower(void)
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{
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unsigned int v;
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asm volatile(
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" mcr p15, 0, %1, c7, c5, 0\n"
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" dsb\n"
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/*
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* Turn off coherency
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*/
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" mrc p15, 0, %0, c1, c0, 1\n"
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" bic %0, %0, #0x20\n"
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" mcr p15, 0, %0, c1, c0, 1\n"
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" mrc p15, 0, %0, c1, c0, 0\n"
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" bic %0, %0, %2\n"
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" mcr p15, 0, %0, c1, c0, 0\n"
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: "=&r" (v)
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: "r" (0), "Ir" (CR_C)
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: "cc", "memory");
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}
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static inline void cpu_leave_lowpower(void)
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{
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unsigned int v;
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asm volatile("mrc p15, 0, %0, c1, c0, 0\n"
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" orr %0, %0, %1\n"
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" mcr p15, 0, %0, c1, c0, 0\n"
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" mrc p15, 0, %0, c1, c0, 1\n"
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" orr %0, %0, #0x20\n"
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" mcr p15, 0, %0, c1, c0, 1\n"
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: "=&r" (v)
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: "Ir" (CR_C)
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: "cc");
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}
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static inline void spear13xx_do_lowpower(unsigned int cpu, int *spurious)
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{
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for (;;) {
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wfi();
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if (spear_pen_release == cpu) {
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/*
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* OK, proper wakeup, we're done
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*/
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break;
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}
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/*
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* Getting here, means that we have come out of WFI without
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* having been woken up - this shouldn't happen
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*
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* Just note it happening - when we're woken, we can report
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* its occurrence.
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*/
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(*spurious)++;
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}
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}
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/*
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* platform-specific code to shutdown a CPU
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*
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* Called with IRQs disabled
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*/
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void spear13xx_cpu_die(unsigned int cpu)
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{
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int spurious = 0;
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/*
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* we're ready for shutdown now, so do it
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*/
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cpu_enter_lowpower();
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spear13xx_do_lowpower(cpu, &spurious);
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/*
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* bring this CPU back into the world of cache
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* coherency, and then restore interrupts
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*/
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cpu_leave_lowpower();
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if (spurious)
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pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
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}
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