The AArch64 TCR_ELx register is a 64-bit register, and many newer architecture features use bits in the upper half. So far U-Boot was igorant of those bits, trying to leave them alone. However, in an effort to set bit 31 to 1, it failed doing so, because the compiler sign-extended "1 << 31", so that all bits[63:31] got set.
Older ARMv8.0 cores don't define anything dangerous up there, but newer architecture revisions do, and setting all those bits will end badly: ================= $ qemu-system-aarch64 -cpu max .... U-Boot 2022.07-rc1 (May 09 2022 - 15:21:00 +0100)
DRAM: 1.5 GiB ================= (hangs here)
Defining TCR_ELx_RSVD to "1U << 31" avoids the sign-extension, so all upper bits stay at a safe 0 value. This means no more surprises when U-Boot runs on a more capable CPU core.
Reported-by: Balaji Anandapadmanaban Balaji.Anandapadmanaban@arm.com Signed-off-by: Andre Przywara andre.przywara@arm.com --- arch/arm/include/asm/armv8/mmu.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/armv8/mmu.h b/arch/arm/include/asm/armv8/mmu.h index fc97c55114..c36b2cf5a5 100644 --- a/arch/arm/include/asm/armv8/mmu.h +++ b/arch/arm/include/asm/armv8/mmu.h @@ -99,9 +99,9 @@ #define TCR_TG0_16K (2 << 14) #define TCR_EPD1_DISABLE (1 << 23)
-#define TCR_EL1_RSVD (1 << 31) -#define TCR_EL2_RSVD (1 << 31 | 1 << 23) -#define TCR_EL3_RSVD (1 << 31 | 1 << 23) +#define TCR_EL1_RSVD (1U << 31) +#define TCR_EL2_RSVD (1U << 31 | 1 << 23) +#define TCR_EL3_RSVD (1U << 31 | 1 << 23)
#ifndef __ASSEMBLY__ static inline void set_ttbr_tcr_mair(int el, u64 table, u64 tcr, u64 attr)