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Maciej W. Rozycki f0a6c68f69 MIPS: Fix CP0 counter erratum detection for R4k CPUs 
Fix the discrepancy between the two places we check for the CP0 counter
erratum in along with the incorrect comparison of the R4400 revision
number against 0x30 which matches none and consistently consider all
R4000 and R4400 processors affected, as documented in processor errata
publications[1][2][3], following the mapping between CP0 PRId register
values and processor models:

  PRId   |  Processor Model
---------+--------------------
00000422 | R4000 Revision 2.2
00000430 | R4000 Revision 3.0
00000440 | R4400 Revision 1.0
00000450 | R4400 Revision 2.0
00000460 | R4400 Revision 3.0

No other revision of either processor has ever been spotted.

Contrary to what has been stated in commit ce202cbb9e ("[MIPS] Assume
R4000/R4400 newer than 3.0 don't have the mfc0 count bug") marking the
CP0 counter as buggy does not preclude it from being used as either a
clock event or a clock source device.  It just cannot be used as both at
a time, because in that case clock event interrupts will be occasionally
lost, and the use as a clock event device takes precedence.

Compare against 0x4ff in `can_use_mips_counter' so that a single machine
instruction is produced.

References:

[1] "MIPS R4000PC/SC Errata, Processor Revision 2.2 and 3.0", MIPS
    Technologies Inc., May 10, 1994, Erratum 53, p.13

[2] "MIPS R4400PC/SC Errata, Processor Revision 1.0", MIPS Technologies
    Inc., February 9, 1994, Erratum 21, p.4

[3] "MIPS R4400PC/SC Errata, Processor Revision 2.0 & 3.0", MIPS
    Technologies Inc., January 24, 1995, Erratum 14, p.3

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Fixes: ce202cbb9e ("[MIPS] Assume R4000/R4400 newer than 3.0 don't have the mfc0 count bug")
Cc: stable@vger.kernel.org # v2.6.24+
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
2022-04-29 15:52:00 +02:00
arch MIPS: Fix CP0 counter erratum detection for R4k CPUs 2022-04-29 15:52:00 +02:00
block block: don't print I/O error warning for dead disks 2022-04-15 06:33:03 -06:00
certs Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
crypto for-5.18/64bit-pi-2022-03-25 2022-03-26 12:01:35 -07:00
Documentation Devicetree fixes for v5.18, part 2: 2022-04-16 17:07:50 -07:00
drivers xen: branch for v5.18-rc3 2022-04-17 10:29:10 -07:00
fs Merge branch 'akpm' (patches from Andrew) 2022-04-15 15:57:18 -07:00
include gpio fixes for v5.18-rc3 2022-04-16 17:01:43 -07:00
init Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
ipc fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
kernel A small set of fixes for the timers core: 2022-04-17 09:53:01 -07:00
lib Driver core changes for 5.18-rc2 2022-04-10 09:55:09 -10:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm: kmemleak: take a full lowmem check in kmemleak_*_phys() 2022-04-15 14:49:56 -07:00
net Networking fixes for 5.18-rc3, including fixes from wireless and 2022-04-14 11:58:19 -07:00
samples dma-mapping updates for Linux 5.18 2022-03-29 08:50:14 -07:00
scripts hardening fixes for v5.18-rc3 2022-04-12 14:29:40 -10:00
security hardening updates for v5.18-rc1-fix1 2022-03-31 11:43:01 -07:00
sound sound fixes for 5.18-rc3 2022-04-14 11:08:12 -07:00
tools Two x86 fixes related to TSX: 2022-04-17 09:55:59 -07:00
usr Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
virt KVM/arm64 fixes for 5.18, take #1 2022-04-08 12:30:04 -04:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update Vasily Averin's email address 2022-04-08 14:20:36 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS ARM: SoC fixes for 5.18, part 2 2022-04-16 16:51:39 -07:00
Makefile Linux 5.18-rc3 2022-04-17 13:57:31 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.