diff mbox

[PATCHv3,03/19] arm64: introduce sysreg_clear_set()

Message ID 20180618120310.39527-4-mark.rutland@arm.com (mailing list archive)
State New, archived
Headers show

Commit Message

Mark Rutland June 18, 2018, 12:02 p.m. UTC
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>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm64/include/asm/sysreg.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

Comments

Catalin Marinas June 19, 2018, 11:44 a.m. UTC | #1
On Mon, Jun 18, 2018 at 01:02:54PM +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>
> Reviewed-by: Dave Martin <dave.martin@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Marc Zyngier June 19, 2018, 11:47 a.m. UTC | #2
On 18/06/18 13:02, 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>
> Reviewed-by: Dave Martin <dave.martin@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Marc Zyngier <marc.zyngier@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 48ad361c178e..fefc17dae8ee 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -731,6 +731,17 @@ 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;
> 

For the record, I have this patch as part of Dave's FPSIMD/SVE fixes.

Thanks,

	M.
diff mbox

Patch

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 48ad361c178e..fefc17dae8ee 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -731,6 +731,17 @@  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;