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Commit 88a06607 authored by Rohit Vaswani's avatar Rohit Vaswani
Browse files

ARM64: spinlock: Add SEV and dsb in unlock code 



In certain unexplained cases, the stlr alone might not wakeup
the processor waiting in WFE on a spinlock.
Add an explicity dsb and SEV in write_unlock, read_unlock
and spin_unlock to ensure that the core waiting on the lock
wakes up from WFE.
Selectable by config option SEV_IN_LOCK_UNLOCK

Change-Id: I691ff5713d4d564623b75b053b40d1f46d74868a
Signed-off-by: default avatarRohit Vaswani <rvaswani@codeaurora.org>
parent b515a7ad

arch/arm64/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -316,6 +316,16 @@ config ARM64_A57_ERRATA_832075 
	  c) Following the branch instruction, there are six or more loads

	  to device memory locations



config ARM64_SEV_IN_LOCK_UNLOCK

	bool "Add explicit SEV in the spinlock unlock code path"

	def_bool ARCH_MSM8994

	help

	  In certain unexplained cases, the stlr alone might not wakeup

	  the processor waiting in WFE on a spinlock.

	  Add an explicity dsb and SEV in write_unlock, read_unlock

	  and spin_unlock to ensure that the core waiting on the lock

	  wakes up from WFE.



config SMP

	bool "Symmetric Multi-Processing"

	help

arch/arm64/include/asm/spinlock.h

+12 −0
Original line number Diff line number Diff line
@@ -86,6 +86,10 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock) 
{

	asm volatile(

"	stlrh	%w1, %0\n"

#ifdef CONFIG_ARM64_SEV_IN_LOCK_UNLOCK

"	dsb sy\n"

"	sev\n"

#endif

	: "=Q" (lock->owner)

	: "r" (lock->owner + 1)

	: "memory");
@@ -155,6 +159,10 @@ static inline void arch_write_unlock(arch_rwlock_t *rw) 
{

	asm volatile(

	"	stlr	%w1, %0\n"

#ifdef CONFIG_ARM64_SEV_IN_LOCK_UNLOCK

	"	dsb sy\n"

	"	sev\n"

#endif

	: "=Q" (rw->lock) : "r" (0) : "memory");

}
@@ -198,6 +206,10 @@ static inline void arch_read_unlock(arch_rwlock_t *rw) 
	"1:	ldxr	%w0, %2\n"

	"	sub	%w0, %w0, #1\n"

	"	stlxr	%w1, %w0, %2\n"

#ifdef CONFIG_ARM64_SEV_IN_LOCK_UNLOCK

	"	dsb sy\n"

	"	sev\n"

#endif

	"	cbnz	%w1, 1b\n"

	: "=&r" (tmp), "=&r" (tmp2), "+Q" (rw->lock)

	: