[PATCH V11 10/17] riscv: qspinlock: errata: Enable qspinlock for T-HEAD processors

[guoren at kernel.org]

From: Guo Ren <guoren at linux.alibaba.com>

According to qspinlock requirements, RISC-V gives out a weak LR/SC
forward progress guarantee which does not satisfy qspinlock. But
many vendors could produce stronger forward guarantee LR/SC to
ensure the xchg_tail could be finished in time on any kind of
hart. T-HEAD is the vendor which implements strong forward
guarantee LR/SC instruction pairs, so enable qspinlock for T-HEAD
with errata init help.

Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Signed-off-by: Guo Ren <guoren at kernel.org>
---
 arch/riscv/errata/thead/errata.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
index 751eb5a7f614..0df6a67302c0 100644
--- a/arch/riscv/errata/thead/errata.c
+++ b/arch/riscv/errata/thead/errata.c
@@ -86,6 +86,13 @@ static bool errata_probe_write_once(unsigned int stage,
 	return false;
 }
 
+extern bool enable_qspinlock_key;
+static void errata_probe_qspinlock(unsigned int stage)
+{
+	if (stage == RISCV_ALTERNATIVES_BOOT)
+		enable_qspinlock_key = true;
+}
+
 static u32 thead_errata_probe(unsigned int stage,
 			      unsigned long archid, unsigned long impid)
 {
@@ -103,6 +110,8 @@ static u32 thead_errata_probe(unsigned int stage,
 	if (errata_probe_write_once(stage, archid, impid))
 		cpu_req_errata |= BIT(ERRATA_THEAD_WRITE_ONCE);
 
+	errata_probe_qspinlock(stage);
+
 	return cpu_req_errata;
 }
 
-- 
2.36.1