arm64: Introduce sysreg_clear_set()

Currently we have a couple of helpers to manipulate bits in particular
sysregs:

 * config_sctlr_el1(u32 clear, u32 set)

 * change_cpacr(u64 val, u64 mask)

The parameters of these differ in naming convention, order, and size,
which is unfortunate. They also differ slightly in behaviour, as
change_cpacr() skips the sysreg write if the bits are unchanged, which
is a useful optimization when sysreg writes are expensive.

Before we gain yet another sysreg manipulation function, let's
unify these with a common helper, providing a consistent order for
clear/set operands, and the write skipping behaviour from
change_cpacr(). Code will be migrated to the new helper in subsequent
patches.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 6171178075dcab62def613141732a0b7601b1c43..a8f84812c6e8925c9429451dc3119bfbd5620e8c 100644 (file)
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -728,6 +728,17 @@ asm(
        asm volatile("msr_s " __stringify(r) ", %x0" : : "rZ" (__val)); \
 } while (0)
 
+/*
+ * Modify bits in a sysreg. Bits in the clear mask are zeroed, then bits in the
+ * set mask are set. Other bits are left as-is.
+ */
+#define sysreg_clear_set(sysreg, clear, set) do {                      \
+       u64 __scs_val = read_sysreg(sysreg);                            \
+       u64 __scs_new = (__scs_val & ~(u64)(clear)) | (set);            \
+       if (__scs_new != __scs_val)                                     \
+               write_sysreg(__scs_new, sysreg);                        \
+} while (0)
+
 static inline void config_sctlr_el1(u32 clear, u32 set)
 {
        u32 val;