On Tue, Sep 02, 2025 at 08:19:30AM +0000, Yao Zi wrote: > Ratified on Apr. 2024, the original RISC-V "A" extension is now split > into two separate extensions, "Zaamo" for atomic operations and "Zalrsc" > for load-reserved/store-conditional instructions. > > For now, we've already seen real-world designs implement the Zalrsc > extension only[2]. As U-Boot mainly runs with only one HART, we could > easily support these designs by not using AMO instructions in the > hard-written assembly if necessary, for which this patch introduces two > new Kconfig options to indicate the availability of "Zaamo" and "Zalrsc". > > Note that even with this patch, "A" extension is specified in the ISA > string passed to the compiler as long as one of "Zaamo" or "Zalrsc" is > available, since they're only recognized with a quite recent version of > GCC/Clang. The compiler usually doesn't automatically generate atomic > instructions unless the source explicitly instructs it to do so, thus > this should be safe. > > Link: > https://github.com/riscv/riscv-zaamo-zalrsc/commit/d94c64c63e9120d56bdeb540caf2e5dae60a8126 > # [1] > Link: > https://lore.kernel.org/u-boot/20250729162035.209849-9-uros.sta...@htecgroup.com/ > # [2] > Signed-off-by: Yao Zi <zi...@disroot.org> > --- > arch/riscv/Kconfig | 17 +++++++++++++++++ > arch/riscv/Makefile | 7 ++++++- > 2 files changed, 23 insertions(+), 1 deletion(-)
Reviewed-by: Leo Yu-Chi Liang <ycli...@andestech.com>
