On Fri, 29 Sept 2023 at 17:07, Jonas Karlman jonas@kwiboo.se wrote:
The alignment hole caused by cmdidx in struct mmc_cmd cause strange issues together with the peephole2 optimization on Amlogic SoCs. Following was observed while working on SPL support for Amlogic SoCs.
sd_get_capabilities() normally issue a CMD55 followed by a CMD51. However, on at least Amlogic S905 (Cortex-A53) and S905X3 (Cortex-A55), CMD55 was instead followed by CMD8 (and a few reties) in SPL.
Code from the call site:
cmd.cmdidx = SD_CMD_APP_SEND_SCR; // 51 ... data.blocksize = 8; ... err = mmc_send_cmd_retry(mmc, &cmd, &data, 3);
Running the code with MMC_TRACE enabled shows:
CMD_SEND:55 ARG 0x50480000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:8 ARG 0x00000000 RET -110
Removing the alignment hole by changing cmdidx from ushort to uint or building with -fno-peephole2 flag seem to resolve this issue.
CMD_SEND:55 ARG 0x50480000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:51 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000920
Same issue was observed building U-Boot with gcc 8-13. Please advise on how to best work around this possible gcc optimization bug.
Signed-off-by: Jonas Karlman jonas@kwiboo.se
arch/arm/cpu/armv8/config.mk | 2 ++ include/mmc.h | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/arm/cpu/armv8/config.mk b/arch/arm/cpu/armv8/config.mk index 4d74b2a533e0..7177dcd7c73b 100644 --- a/arch/arm/cpu/armv8/config.mk +++ b/arch/arm/cpu/armv8/config.mk @@ -7,6 +7,8 @@ PLATFORM_RELFLAGS += $(call cc-option,-mbranch-protection=none) PF_NO_UNALIGNED := $(call cc-option, -mstrict-align) PLATFORM_CPPFLAGS += $(PF_NO_UNALIGNED)
+PLATFORM_CPPFLAGS += $(call cc-option,-fno-peephole2)
Eek really?
EFI_LDS := elf_aarch64_efi.lds EFI_CRT0 := crt0_aarch64_efi.o EFI_RELOC := reloc_aarch64_efi.o diff --git a/include/mmc.h b/include/mmc.h index 9aef31ea5deb..7b3868bb5664 100644 --- a/include/mmc.h +++ b/include/mmc.h @@ -413,7 +413,7 @@ struct mmc_cid { };
struct mmc_cmd {
ushort cmdidx;
uint cmdidx;
This bit looks OK.
uint resp_type; uint cmdarg; uint response[4];-- 2.42.0
Regards, Simon