[PATCH 03/15] ARM: rework ARM11 CPU selection logic
From: Arnd Bergmann
Date: Wed Dec 04 2024 - 05:30:14 EST
From: Arnd Bergmann <arnd@xxxxxxxx>
Support for SMP on ARM1136r0 has been broken for a while, and nobody
is working on fixing it. I had a plan to change ARMv6 support to no
longer coexist in a common kernel with ARMv7 CPUs but instead ARMv5 and
below. This would have addressed the problem, but after a recent mailing
list discussion, we concluded that an easier approach is to just forbid
ARM1136r0 CPU support on SMP-enabled kernels.
This mainly affects users of the Nokia N800/N810 tablets using an
OMAP2420 SoC, which is the only commercial product with an ARM1136r0
that is still supported by the kernel.
The other machines that are still in the same hardware catogory are:
- TI OMAP2420 H4 reference board
- TI OMAP2430 SDP software development platform
- Freescale/NXP i.MX31 Lite Development Kit
- Buglabs i.MX31 Bug 1.x prototype
- Arm Integrator/AP with CM1136JF-S core module
To my knowledge, none of these have any actual users aside from
reference boards being used more easily test the platforms.
There are also a few ARM1136r1 machines, which implement the
ARMv6K SMP support (barriers, atomics and TLS):
- Eukrea CPUIMX35 reference platform
- Freescale/NXP i.MX35 Product Development Kit
- ARM Integrator/CP/IM-LT3 with ARM1136J Core Tile
- ARM Realview/EB with ARM1136J Core Tile
Again, these are mainly reference implementations rather than
actual products, but since they support ARMv6K, they should
continue to work correctly in SMP-enabled kernels. For the
ARM Core Tile, I have not found a datasheet but instead use
the revision based on what the respective virtual models
report.
All the other ARMv6 platforms use an ARM1176 with ARMv6K,
VMSAv7 and Trustzone support.
To avoid the broken configuration, annotate the ARM1136 based
machines with specific CPU_ARM1136R0 or CPU_ARM1136R2 symbols
in Kconfig and make the r0 variants depend on !SMP.
Link: https://lore.kernel.org/linux-arm-kernel/2831c5a6-cfbf-4fe0-b51c-0396e5b0aeb7@xxxxxxxxxxxxxxxx/T/
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
arch/arm/Kconfig.platforms | 2 +-
arch/arm/mach-imx/Kconfig | 3 ++-
arch/arm/mach-omap2/Kconfig | 2 +-
arch/arm/mach-versatile/Kconfig | 10 +++++-----
arch/arm/mm/Kconfig | 24 +++++++++++++++++++++++-
5 files changed, 32 insertions(+), 9 deletions(-)
diff --git a/arch/arm/Kconfig.platforms b/arch/arm/Kconfig.platforms
index 845ab08e20a4..e56d47eadfdf 100644
--- a/arch/arm/Kconfig.platforms
+++ b/arch/arm/Kconfig.platforms
@@ -37,7 +37,7 @@ config ARCH_MULTI_V4_V5
config ARCH_MULTI_V6
bool "ARMv6 based platforms (ARM11)"
select ARCH_MULTI_V6_V7
- select CPU_V6K
+ select CPU_1176
config ARCH_MULTI_V7
bool "ARMv7 based platforms (Cortex-A, PJ4, Scorpion, Krait)"
diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
index e4fe059cd861..dce9cfc510b7 100644
--- a/arch/arm/mach-imx/Kconfig
+++ b/arch/arm/mach-imx/Kconfig
@@ -40,13 +40,14 @@ comment "ARM1136 platforms"
config SOC_IMX31
bool "i.MX31 support"
- select CPU_V6
+ select CPU_ARM1136R0
select MXC_AVIC
help
This enables support for Freescale i.MX31 processor
config SOC_IMX35
bool "i.MX35 support"
+ select CPU_ARM1136R1
select MXC_AVIC
help
This enables support for Freescale i.MX35 processor
diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
index 821727eefd5a..c2b379850f59 100644
--- a/arch/arm/mach-omap2/Kconfig
+++ b/arch/arm/mach-omap2/Kconfig
@@ -9,7 +9,7 @@ config ARCH_OMAP2
bool "TI OMAP2"
depends on ARCH_MULTI_V6
select ARCH_OMAP2PLUS
- select CPU_V6
+ select CPU_ARM1136R0
select OMAP_HWMOD
select SOC_HAS_OMAP2_SDRC
diff --git a/arch/arm/mach-versatile/Kconfig b/arch/arm/mach-versatile/Kconfig
index 513618078440..de42da7de8c8 100644
--- a/arch/arm/mach-versatile/Kconfig
+++ b/arch/arm/mach-versatile/Kconfig
@@ -113,7 +113,8 @@ config INTEGRATOR_CM1136JFS
bool "Integrator/CM1136JF-S core module"
depends on ARCH_INTEGRATOR_AP
depends on ARCH_MULTI_V6
- select CPU_V6
+ depends on !SMP
+ select CPU_ARM1136R0
config ARCH_INTEGRATOR_CP
bool "Support Integrator/CP platform"
@@ -135,7 +136,7 @@ config INTEGRATOR_CTB36
bool "Integrator/CTB36 (ARM1136JF-S) core tile"
depends on ARCH_INTEGRATOR_CP
depends on ARCH_MULTI_V6
- select CPU_V6
+ select CPU_ARM1136R1
config ARCH_CINTEGRATOR
depends on ARCH_INTEGRATOR_CP
@@ -182,7 +183,7 @@ config MACH_REALVIEW_EB
config REALVIEW_EB_ARM1136
bool "Support ARM1136J(F)-S Tile"
depends on MACH_REALVIEW_EB && ARCH_MULTI_V6
- select CPU_V6
+ select CPU_ARM1136R1
help
Enable support for the ARM1136 tile fitted to the
Realview(R) Emulation Baseboard platform.
@@ -201,11 +202,10 @@ config REALVIEW_EB_A9MP
Enable support for the Cortex-A9MPCore tile fitted to the
Realview(R) Emulation Baseboard platform.
-# ARMv6 CPU without K extensions, but does have the new exclusive ops
config MACH_REALVIEW_PB1176
bool "Support RealView(R) Platform Baseboard for ARM1176JZF-S"
depends on ARCH_MULTI_V6
- select CPU_V6
+ select CPU_ARM1176
select HAVE_TCM
help
Include support for the ARM(R) RealView(R) Platform Baseboard for
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 2b6f50dd5478..f5c1c6f82892 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -376,6 +376,7 @@ config CPU_PJ4B
# ARMv6
config CPU_V6
bool
+ depends on !SMP
select CPU_32v6
select CPU_ABRT_EV6
select CPU_CACHE_V6
@@ -386,7 +387,6 @@ config CPU_V6
select CPU_PABRT_V6
select CPU_THUMB_CAPABLE
select CPU_TLB_V6 if MMU
- select SMP_ON_UP if SMP
# ARMv6k
config CPU_V6K
@@ -403,6 +403,28 @@ config CPU_V6K
select CPU_THUMB_CAPABLE
select CPU_TLB_V6 if MMU
+config CPU_ARM1136R0
+ bool
+ select CPU_V6
+ depends on !SMP
+ help
+ These early revisions of ARM1136 lack support for the
+ ARMv6k extensions for multiprocessing.
+
+config CPU_ARM1136R1
+ bool
+ select CPU_V6K
+ help
+ Later revisions of ARM1136 add ARMv6k (atomics, barriers
+ and TLS register) in addition to the features from r0.
+
+config CPU_ARM1176
+ bool
+ select CPU_V6K
+ help
+ ARM1176 implements ARMv6k, VMSAv7 and Trustzone in
+ addition to the ARMv6 baseline.
+
# ARMv7 and ARMv8 architectures
config CPU_V7
bool
--
2.39.5