linux_dsm_epyc7002/arch/arm/mach-prima2/common.h
Russell King 6213f70e7c ARM: smp: remove arch-provided "pen_release"
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>
2019-02-01 22:05:23 +00:00

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C

/*
* This file contains common function prototypes to avoid externs in the c files.
*
* Copyright (c) 2011 Cambridge Silicon Radio Limited, a CSR plc group company.
*
* Licensed under GPLv2 or later.
*/
#ifndef __MACH_PRIMA2_COMMON_H__
#define __MACH_PRIMA2_COMMON_H__
#include <linux/init.h>
#include <linux/reboot.h>
#include <asm/mach/time.h>
#include <asm/exception.h>
extern volatile int prima2_pen_release;
extern const struct smp_operations sirfsoc_smp_ops;
extern void sirfsoc_secondary_startup(void);
extern void sirfsoc_cpu_die(unsigned int cpu);
extern void __init sirfsoc_of_irq_init(void);
extern asmlinkage void __exception_irq_entry sirfsoc_handle_irq(struct pt_regs *regs);
#ifdef CONFIG_SUSPEND
extern int sirfsoc_pm_init(void);
#else
static inline int sirfsoc_pm_init(void) { return 0; }
#endif
#endif