mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-20 12:10:01 +07:00
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>
48 lines
1.1 KiB
ArmAsm
48 lines
1.1 KiB
ArmAsm
/*
|
|
* arch/arm/mach-spear13XX/headsmp.S
|
|
*
|
|
* Picked from realview
|
|
* Copyright (c) 2012 ST Microelectronics Limited
|
|
* Shiraz Hashim <shiraz.linux.kernel@gmail.com>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
|
|
#include <linux/linkage.h>
|
|
#include <linux/init.h>
|
|
|
|
__INIT
|
|
|
|
/*
|
|
* spear13xx specific entry point for secondary CPUs. This provides
|
|
* a "holding pen" into which all secondary cores are held until we're
|
|
* ready for them to initialise.
|
|
*/
|
|
ENTRY(spear13xx_secondary_startup)
|
|
mrc p15, 0, r0, c0, c0, 5
|
|
and r0, r0, #15
|
|
adr r4, 1f
|
|
ldmia r4, {r5, r6}
|
|
sub r4, r4, r5
|
|
add r6, r6, r4
|
|
pen: ldr r7, [r6]
|
|
cmp r7, r0
|
|
bne pen
|
|
|
|
/* re-enable coherency */
|
|
mrc p15, 0, r0, c1, c0, 1
|
|
orr r0, r0, #(1 << 6) | (1 << 0)
|
|
mcr p15, 0, r0, c1, c0, 1
|
|
/*
|
|
* we've been released from the holding pen: secondary_stack
|
|
* should now contain the SVC stack for this core
|
|
*/
|
|
b secondary_startup
|
|
|
|
.align
|
|
1: .long .
|
|
.long spear_pen_release
|
|
ENDPROC(spear13xx_secondary_startup)
|