| Message ID | 1455804123-2526139-2-git-send-email-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 18 Feb 2016, Arnd Bergmann wrote: > When configuring the kernel for big-endian, we set either BE-8 or BE-32 > based on the CPU architecture level. Until linux-4.4, we did not have > any ARMv7-M platform allowing big-endian builds, but now i.MX/Vybrid > is in that category, adn we get a build error because of this: > > arch/arm/kernel/module-plts.c: In function 'get_module_plt': > arch/arm/kernel/module-plts.c:60:46: error: implicit declaration of function '__opcode_to_mem_thumb32' [-Werror=implicit-function-declaration] > > This comes down to picking the wrong default, ARMv7-M uses BE8 > like ARMv7-A does. Changing the default gets the kernel to compile > and presumably works. Was it tested without BE8 when it was submitted upstream? I don't think you can switch this freely on a given hardware platform and expect it to still work. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > arch/arm/mm/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig > index 55347662e5ed..ff1637365494 100644 > --- a/arch/arm/mm/Kconfig > +++ b/arch/arm/mm/Kconfig > @@ -723,7 +723,7 @@ config CPU_BIG_ENDIAN > config CPU_ENDIAN_BE8 > bool > depends on CPU_BIG_ENDIAN > - default CPU_V6 || CPU_V6K || CPU_V7 > + default CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M > help > Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors. > > -- > 2.7.0 > >
On Thursday 18 February 2016 11:06:08 Nicolas Pitre wrote: > On Thu, 18 Feb 2016, Arnd Bergmann wrote: > > > When configuring the kernel for big-endian, we set either BE-8 or BE-32 > > based on the CPU architecture level. Until linux-4.4, we did not have > > any ARMv7-M platform allowing big-endian builds, but now i.MX/Vybrid > > is in that category, adn we get a build error because of this: > > > > arch/arm/kernel/module-plts.c: In function 'get_module_plt': > > arch/arm/kernel/module-plts.c:60:46: error: implicit declaration of function '__opcode_to_mem_thumb32' [-Werror=implicit-function-declaration] > > > > This comes down to picking the wrong default, ARMv7-M uses BE8 > > like ARMv7-A does. Changing the default gets the kernel to compile > > and presumably works. > > Was it tested without BE8 when it was submitted upstream? I don't think > you can switch this freely on a given hardware platform and expect it to > still work. > > mach-imx contains a number of different SoCs, and one SoC was recently tested successfully after a number of endianess bugs got fixed. This was an i.mx6 using a Cortex-A9 core, but we are now also able to build vybrid vf610 big-endian based on that selection. This SoC supports Linux running either on its Cortex-A5 or its Cortex-M3 (or M4?) cores. I am rather sure nobody has ever run Linux in big-endian mode on the Cortex-M platform, specifically because it was always wrong and could not be enabled in Kconfig. Arnd
On 18/02/16 16:12, Arnd Bergmann wrote: > On Thursday 18 February 2016 11:06:08 Nicolas Pitre wrote: >> On Thu, 18 Feb 2016, Arnd Bergmann wrote: >> >>> When configuring the kernel for big-endian, we set either BE-8 or BE-32 >>> based on the CPU architecture level. Until linux-4.4, we did not have >>> any ARMv7-M platform allowing big-endian builds, but now i.MX/Vybrid >>> is in that category, adn we get a build error because of this: >>> >>> arch/arm/kernel/module-plts.c: In function 'get_module_plt': >>> arch/arm/kernel/module-plts.c:60:46: error: implicit declaration of function '__opcode_to_mem_thumb32' [-Werror=implicit-function-declaration] >>> >>> This comes down to picking the wrong default, ARMv7-M uses BE8 >>> like ARMv7-A does. Changing the default gets the kernel to compile >>> and presumably works. >> >> Was it tested without BE8 when it was submitted upstream? I don't think >> you can switch this freely on a given hardware platform and expect it to >> still work. >> >> > > mach-imx contains a number of different SoCs, and one SoC was recently > tested successfully after a number of endianess bugs got fixed. This was > an i.mx6 using a Cortex-A9 core, but we are now also able to build > vybrid vf610 big-endian based on that selection. This SoC supports > Linux running either on its Cortex-A5 or its Cortex-M3 (or M4?) cores. > > I am rather sure nobody has ever run Linux in big-endian mode on the > Cortex-M platform, specifically because it was always wrong and could > not be enabled in Kconfig. Ah, it explains why my quick attempt to enable BE for MPS2 (M-class platform) failed. With this patch applied I'm able to see Linux booting on MPS2 FVP model in BE, not complete boot but it might be due to other reasons. So this patch definitely improves things for me, if it helps Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> Cheers Vladimir > > Arnd > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > >
On Friday 19 February 2016 08:47:47 Vladimir Murzin wrote: > Ah, it explains why my quick attempt to enable BE for MPS2 (M-class > platform) failed. With this patch applied I'm able to see Linux booting > on MPS2 FVP model in BE, not complete boot but it might be due to other > reasons. So this patch definitely improves things for me, if it helps > > Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> > Awesome, thanks for testing! Arnd
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index 55347662e5ed..ff1637365494 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -723,7 +723,7 @@ config CPU_BIG_ENDIAN config CPU_ENDIAN_BE8 bool depends on CPU_BIG_ENDIAN - default CPU_V6 || CPU_V6K || CPU_V7 + default CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M help Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors.
When configuring the kernel for big-endian, we set either BE-8 or BE-32 based on the CPU architecture level. Until linux-4.4, we did not have any ARMv7-M platform allowing big-endian builds, but now i.MX/Vybrid is in that category, adn we get a build error because of this: arch/arm/kernel/module-plts.c: In function 'get_module_plt': arch/arm/kernel/module-plts.c:60:46: error: implicit declaration of function '__opcode_to_mem_thumb32' [-Werror=implicit-function-declaration] This comes down to picking the wrong default, ARMv7-M uses BE8 like ARMv7-A does. Changing the default gets the kernel to compile and presumably works. Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- arch/arm/mm/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)