Re: [boot-wrapper PATCH] Allow --enable-psci to choose between smc and hvc

[Qi Feng <qi.feng@arm.com>]

Any comments for this patch?

On 6/18/21 11:22 AM, Qi Feng wrote:
> According to Armv8-R AArch64 manual [1], Armv8-R AArch64 does not
> support smc:
> 
> - Pseudocode for AArch64.CheckForSMCUndefOrTrap has this snippet:
> 
>        if !HaveEL(EL3) || PSTATE.EL == EL0 then
>            UNDEFINED;
> 
>    And Armv8-R AArch64 does not have EL3.
> 
> - In the document of HCR_EL2 TSC bit:
>    If EL3 is not implemented and HCR_EL2.NV is 0, it is IMPLEMENTATION
>    DEFINED whether this bit is:
>    - RES0.
>    - Implemented with the functionality as described in HCR_EL2.TSC.
> 
> So hvc is needed in this situation. And due to the lack of libfdt, the
> psci method cannot be modified at runtime.
> 
> To use smc, use --enable-psci or --enable-psci=smc.
> To use hvc, use --enable-psci=hvc.
> 
> [1]: https://developer.arm.com/documentation/ddi0600/latest/
> 
> Signed-off-by: Qi Feng <qi.feng@arm.com>
> ---
>   Makefile.am  |  2 +-
>   configure.ac | 14 +++++++++-----
>   2 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/Makefile.am b/Makefile.am
> index ef6b793..a9ddd16 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -47,7 +47,7 @@ BOOTMETHOD	:= psci.o
>   OFILES		+= psci.o
>   PSCI_NODE	:= psci {				\
>   			compatible = \"arm,psci\";	\
> -			method = \"smc\";		\
> +			method = \"$(PSCI_METHOD)\";	\
>   			cpu_on = <$(PSCI_CPU_ON)>;	\
>   			cpu_off = <$(PSCI_CPU_OFF)>;	\
>   		   };
> diff --git a/configure.ac b/configure.ac
> index 6914eb4..9aab4a1 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -83,13 +83,17 @@ AS_IF([test "x$X_IMAGE" != "x"],
>   # Allow a user to pass --enable-psci
>   AC_ARG_ENABLE([psci],
>   	AS_HELP_STRING([--enable-psci], [enable the psci boot method]),
> -	[USE_PSCI=$enableval])
> -AM_CONDITIONAL([PSCI], [test "x$USE_PSCI" = "xyes"])
> -AS_IF([test "x$USE_PSCI" = "xyes"], [], [USE_PSCI=no])
> -
> -AS_IF([test "x$USE_PSCI" != "xyes" -a "x$KERNEL_ES" = "x32"],
> +	[case "${enableval}" in
> +		yes|smc) USE_PSCI=smc ;;
> +		hvc) USE_PSCI=hvc ;;
> +		*) AC_MSG_ERROR([Bad value "${enableval}" for --enable-psci. Use "smc" or "hvc"]) ;;
> +	esac])
> +AM_CONDITIONAL([PSCI], [test "x$USE_PSCI" = "xyes" -o "x$USE_PSCI" = "xsmc" -o "x$USE_PSCI" = "xhvc"])
> +
> +AS_IF([test "x$USE_PSCI" = "xno" -a "x$KERNEL_ES" = "x32"],
>   	[AC_MSG_ERROR([With an AArch32 kernel, boot method must be PSCI.])]
>   )
> +AC_SUBST([PSCI_METHOD], [$USE_PSCI])
>   
>   # Allow a user to pass --with-initrd
>   AC_ARG_WITH([initrd],
> 

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel