feat(aarch64): make ID system register reads non-volatile
Our system register access function wrappers are using "volatile"
inline assembly instructions. On the first glance this is a good idea,
since many system registers have side effects, and we don't want the
compiler to optimise or reorder them (what "volatile" prevents).
However this also naturally limits the compiler's freedom to optimise
code better, and those volatile properties don't apply to every type of
system register. One example are the CPU ID registers, which have
constant values, are side-effect free and read-only.
Introduce a new wrapper type that drops the volatile keyword, and use
that for the wrappers instantiating ID register accessors.
This allows the compiler to freely optimise those instructions away, if
their result isn't actually used, which can trigger further
optimisations.
Change-Id: I3c64716ae4f4bf603f0ea57b652bd50bcc67bb0e
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/include/arch/aarch64/arch_helpers.h b/include/arch/aarch64/arch_helpers.h
index fe9b5a5..5010ac5 100644
--- a/include/arch/aarch64/arch_helpers.h
+++ b/include/arch/aarch64/arch_helpers.h
@@ -27,6 +27,14 @@
return v; \
}
+#define _DEFINE_SYSREG_READ_FUNC_NV(_name, _reg_name) \
+static inline u_register_t read_ ## _name(void) \
+{ \
+ u_register_t v; \
+ __asm__ ("mrs %0, " #_reg_name : "=r" (v)); \
+ return v; \
+}
+
#define _DEFINE_SYSREG_WRITE_FUNC(_name, _reg_name) \
static inline void write_ ## _name(u_register_t v) \
{ \
@@ -58,6 +66,14 @@
#define DEFINE_RENAME_SYSREG_WRITE_FUNC(_name, _reg_name) \
_DEFINE_SYSREG_WRITE_FUNC(_name, _reg_name)
+/* Define read function for ID register (w/o volatile qualifier) */
+#define DEFINE_IDREG_READ_FUNC(_name) \
+ _DEFINE_SYSREG_READ_FUNC_NV(_name, _name)
+
+/* Define read function for renamed ID register (w/o volatile qualifier) */
+#define DEFINE_RENAME_IDREG_READ_FUNC(_name, _reg_name) \
+ _DEFINE_SYSREG_READ_FUNC_NV(_name, _reg_name)
+
/**********************************************************************
* Macros to create inline functions for system instructions
*********************************************************************/
@@ -247,14 +263,14 @@
#define write_daifset(val) SYSREG_WRITE_CONST(daifset, val)
DEFINE_SYSREG_RW_FUNCS(par_el1)
-DEFINE_SYSREG_READ_FUNC(id_pfr1_el1)
-DEFINE_SYSREG_READ_FUNC(id_aa64isar0_el1)
-DEFINE_SYSREG_READ_FUNC(id_aa64isar1_el1)
-DEFINE_RENAME_SYSREG_READ_FUNC(id_aa64isar2_el1, ID_AA64ISAR2_EL1)
-DEFINE_SYSREG_READ_FUNC(id_aa64pfr0_el1)
-DEFINE_SYSREG_READ_FUNC(id_aa64pfr1_el1)
-DEFINE_SYSREG_READ_FUNC(id_aa64dfr0_el1)
-DEFINE_SYSREG_READ_FUNC(id_afr0_el1)
+DEFINE_IDREG_READ_FUNC(id_pfr1_el1)
+DEFINE_IDREG_READ_FUNC(id_aa64isar0_el1)
+DEFINE_IDREG_READ_FUNC(id_aa64isar1_el1)
+DEFINE_RENAME_IDREG_READ_FUNC(id_aa64isar2_el1, ID_AA64ISAR2_EL1)
+DEFINE_IDREG_READ_FUNC(id_aa64pfr0_el1)
+DEFINE_IDREG_READ_FUNC(id_aa64pfr1_el1)
+DEFINE_IDREG_READ_FUNC(id_aa64dfr0_el1)
+DEFINE_IDREG_READ_FUNC(id_afr0_el1)
DEFINE_SYSREG_READ_FUNC(CurrentEl)
DEFINE_SYSREG_READ_FUNC(ctr_el0)
DEFINE_SYSREG_RW_FUNCS(daif)
@@ -367,10 +383,10 @@
/*******************************************************************************
* System register accessor prototypes
******************************************************************************/
-DEFINE_SYSREG_READ_FUNC(midr_el1)
+DEFINE_IDREG_READ_FUNC(midr_el1)
DEFINE_SYSREG_READ_FUNC(mpidr_el1)
-DEFINE_SYSREG_READ_FUNC(id_aa64mmfr0_el1)
-DEFINE_SYSREG_READ_FUNC(id_aa64mmfr1_el1)
+DEFINE_IDREG_READ_FUNC(id_aa64mmfr0_el1)
+DEFINE_IDREG_READ_FUNC(id_aa64mmfr1_el1)
DEFINE_SYSREG_RW_FUNCS(scr_el3)
DEFINE_SYSREG_RW_FUNCS(hcr_el2)
@@ -516,7 +532,7 @@
DEFINE_RENAME_SYSREG_WRITE_FUNC(zcr_el3, ZCR_EL3)
DEFINE_RENAME_SYSREG_WRITE_FUNC(zcr_el2, ZCR_EL2)
-DEFINE_RENAME_SYSREG_READ_FUNC(id_aa64smfr0_el1, ID_AA64SMFR0_EL1)
+DEFINE_RENAME_IDREG_READ_FUNC(id_aa64smfr0_el1, ID_AA64SMFR0_EL1)
DEFINE_RENAME_SYSREG_RW_FUNCS(smcr_el3, SMCR_EL3)
DEFINE_RENAME_SYSREG_READ_FUNC(erridr_el1, ERRIDR_EL1)
@@ -530,7 +546,7 @@
DEFINE_RENAME_SYSREG_READ_FUNC(erxmisc1_el1, ERXMISC1_EL1)
/* Armv8.2 Registers */
-DEFINE_RENAME_SYSREG_READ_FUNC(id_aa64mmfr2_el1, ID_AA64MMFR2_EL1)
+DEFINE_RENAME_IDREG_READ_FUNC(id_aa64mmfr2_el1, ID_AA64MMFR2_EL1)
/* Armv8.3 Pointer Authentication Registers */
DEFINE_RENAME_SYSREG_RW_FUNCS(apiakeyhi_el1, APIAKeyHi_EL1)
diff --git a/plat/qti/common/src/qti_pm.c b/plat/qti/common/src/qti_pm.c
index 5f1b7aa..ae361e9 100644
--- a/plat/qti/common/src/qti_pm.c
+++ b/plat/qti/common/src/qti_pm.c
@@ -47,8 +47,7 @@
#define QTI_CORE_PWRDN_EN_MASK 1
/* cpu power control happens to be same across all CPUs */
-_DEFINE_SYSREG_WRITE_FUNC(cpu_pwrctrl_val, S3_0_C15_C2_7)
-_DEFINE_SYSREG_READ_FUNC(cpu_pwrctrl_val, S3_0_C15_C2_7)
+DEFINE_RENAME_SYSREG_RW_FUNCS(cpu_pwrctrl_val, S3_0_C15_C2_7)
const unsigned int qti_pm_idle_states[] = {
qti_make_pwrstate_lvl0(QTI_LOCAL_STATE_OFF,