2021-07-25 13:04:16

by Geert Uytterhoeven

Subject: [PATCH] m68k: Fix invalid RMW_INSNS on CPUs that lack CAS

When enabling CONFIG_RMW_INSNS in e.g. a Coldfire build:

{standard input}:3068: Error: invalid instruction for this architecture; needs 68020 or higher (68020 [68k, 68ec020], 68030 [68ec030], 68040 [68ec040], 68060 [68ec060]) -- statement `casl %d4,%d0,(%a6)' ignored

Fix this by (a) adding a new config symbol to track if support for any
CPU that lacks the CAS instruction is enabled, and (b) making
CONFIG_RMW_INSNS depend on the new symbol not being set.

Fixes: 0e152d80507b75c0 ("m68k: reorganize Kconfig options to improve mmu/non-mmu selections")
Reported-by: kernel test robot <[email protected]>
Reported-by: Arnd Bergmann <[email protected]>
Signed-off-by: Geert Uytterhoeven <[email protected]>
---
arch/m68k/Kconfig.cpu | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/m68k/Kconfig.cpu b/arch/m68k/Kconfig.cpu
index 29e946394fdb4017..277d61a094637ce3 100644
--- a/arch/m68k/Kconfig.cpu
+++ b/arch/m68k/Kconfig.cpu
@@ -26,6 +26,7 @@ config COLDFIRE
bool "Coldfire CPU family support"
select ARCH_HAVE_CUSTOM_GPIO_H
select CPU_HAS_NO_BITFIELDS
+ select CPU_HAS_NO_CAS
select CPU_HAS_NO_MULDIV64
select GENERIC_CSUM
select GPIOLIB
@@ -39,6 +40,7 @@ config M68000
bool
depends on !MMU
select CPU_HAS_NO_BITFIELDS
+ select CPU_HAS_NO_CAS
select CPU_HAS_NO_MULDIV64
select CPU_HAS_NO_UNALIGNED
select GENERIC_CSUM
@@ -54,6 +56,7 @@ config M68000
config MCPU32
bool
select CPU_HAS_NO_BITFIELDS
+ select CPU_HAS_NO_CAS
select CPU_HAS_NO_UNALIGNED
select CPU_NO_EFFICIENT_FFS
help
@@ -383,7 +386,7 @@ config ADVANCED

config RMW_INSNS
bool "Use read-modify-write instructions"
- depends on ADVANCED
+ depends on ADVANCED && !CPU_HAS_NO_CAS
help
This allows to use certain instructions that work with indivisible
read-modify-write bus cycles. While this is faster than the
@@ -450,6 +453,9 @@ config M68K_L2_CACHE
config CPU_HAS_NO_BITFIELDS
bool

+config CPU_HAS_NO_CAS
+ bool
+
config CPU_HAS_NO_MULDIV64
bool

--
2.25.1

2021-07-25 15:27:26

by Arnd Bergmann

Subject: Re: [PATCH] m68k: Fix invalid RMW_INSNS on CPUs that lack CAS

On Sun, Jul 25, 2021 at 3:02 PM Geert Uytterhoeven <[email protected]> wrote:
>
> When enabling CONFIG_RMW_INSNS in e.g. a Coldfire build:
>
> {standard input}:3068: Error: invalid instruction for this architecture; needs 68020 or higher (68020 [68k, 68ec020], 68030 [68ec030], 68040 [68ec040], 68060 [68ec060]) -- statement `casl %d4,%d0,(%a6)' ignored
>
> Fix this by (a) adding a new config symbol to track if support for any
> CPU that lacks the CAS instruction is enabled, and (b) making
> CONFIG_RMW_INSNS depend on the new symbol not being set.
>
> Fixes: 0e152d80507b75c0 ("m68k: reorganize Kconfig options to improve mmu/non-mmu selections")
> Reported-by: kernel test robot <[email protected]>
> Reported-by: Arnd Bergmann <[email protected]>
> Signed-off-by: Geert Uytterhoeven <[email protected]>

Acked-by: Arnd Bergmann <[email protected]>

> @@ -54,6 +56,7 @@ config M68000
> config MCPU32
> bool
> select CPU_HAS_NO_BITFIELDS
> + select CPU_HAS_NO_CAS
> select CPU_HAS_NO_UNALIGNED
> select CPU_NO_EFFICIENT_FFS
> help

As far as I can see, there are no users for CONFIG_MCPU32
after M68360 was removed in linux-4.6, but as long as the
option is there, it makes sense to keep it correct.

Arnd