[03/18] arm64: introduce sysreg_clear_set()

Message ID 20180514094640.27569-4-mark.rutland@arm.com
State Superseded
Headers show
Series
  • arm64: invoke syscalls with pt_regs
Related show

Commit Message

Mark Rutland May 14, 2018, 9:46 a.m.
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 more 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>

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Martin <dave.martin@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm64/include/asm/sysreg.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

-- 
2.11.0

Comments

Dave Martin May 14, 2018, 10:04 a.m. | #1
On Mon, May 14, 2018 at 10:46:25AM +0100, Mark Rutland wrote:
> 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 more 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>

> Cc: Catalin Marinas <catalin.marinas@arm.com>

> Cc: Dave Martin <dave.martin@arm.com>

> Cc: Marc Zyngier <marc.zyngier@arm.com>


Makes sense.  I felt I was (re)inventing an idiom with
change_cpacr() at the time, though it didn't quite seem worth
factoring out.  Now you plan to add a third similar manipulator,
this factoring makes sense.

Reviewed-by: Dave Martin <Dave.Martin@arm.com>


> ---

>  arch/arm64/include/asm/sysreg.h | 11 +++++++++++

>  1 file changed, 11 insertions(+)

> 

> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h

> index bd1d1194a5e7..b52762769329 100644

> --- a/arch/arm64/include/asm/sysreg.h

> +++ b/arch/arm64/include/asm/sysreg.h

> @@ -729,6 +729,17 @@ 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;

> -- 

> 2.11.0

> 

> 

> _______________________________________________

> linux-arm-kernel mailing list

> linux-arm-kernel@lists.infradead.org

> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Patch

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index bd1d1194a5e7..b52762769329 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -729,6 +729,17 @@  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;