Commit 71ce1ae5 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

arm64: sve: Provide a conditional update accessor for ZCR_ELx 



A common pattern is to conditionally update ZCR_ELx in order
to avoid the "self-synchronizing" effect that writing to this
register has.

Let's provide an accessor that does exactly this.

Acked-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 468f3477

arch/arm64/include/asm/fpsimd.h

+9 −0
Original line number Diff line number Diff line
@@ -130,6 +130,15 @@ static inline void sve_user_enable(void) 
	sysreg_clear_set(cpacr_el1, 0, CPACR_EL1_ZEN_EL0EN);

}



#define sve_cond_update_zcr_vq(val, reg)		\

	do {						\

		u64 __zcr = read_sysreg_s((reg));	\

		u64 __new = __zcr & ~ZCR_ELx_LEN_MASK;	\

		__new |= (val) & ZCR_ELx_LEN_MASK;	\

		if (__zcr != __new)			\

			write_sysreg_s(__new, (reg));	\

	} while (0)



/*

 * Probing and setup functions.

 * Calls to these functions must be serialised with one another.