linux-kernel - [PATCH AUTOSEL 5.1 52/95] riscv: Fix udelay in RV32.

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Date:   Wed, 26 Jun 2019 20:29:37 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Nick Hu <nickhu@...estech.com>, Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Sasha Levin <sashal@...nel.org>,
        linux-riscv@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.1 52/95] riscv: Fix udelay in RV32.

From: Nick Hu <nickhu@...estech.com>

[ Upstream commit d0e1f2110a5eeb6e410b2dd37d98bc5b30da7bc7 ]

In RV32, udelay would delay the wrong cycle. When it shifts right
"UDELAY_SHIFT" bits, it either delays 0 cycle or 1 cycle. It only works
correctly in RV64. Because the 'ucycles' always needs to be 64 bits
variable.

Signed-off-by: Nick Hu <nickhu@...estech.com>
Reviewed-by: Palmer Dabbelt <palmer@...ive.com>
[paul.walmsley@...ive.com: fixed minor spelling error]
Signed-off-by: Paul Walmsley <paul.walmsley@...ive.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/riscv/lib/delay.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/lib/delay.c b/arch/riscv/lib/delay.c
index dce8ae24c6d3..ee6853c1e341 100644
--- a/arch/riscv/lib/delay.c
+++ b/arch/riscv/lib/delay.c
@@ -88,7 +88,7 @@ EXPORT_SYMBOL(__delay);
 
 void udelay(unsigned long usecs)
 {
-	unsigned long ucycles = usecs * lpj_fine * UDELAY_MULT;
+	u64 ucycles = (u64)usecs * lpj_fine * UDELAY_MULT;
 
 	if (unlikely(usecs > MAX_UDELAY_US)) {
 		__delay((u64)usecs * riscv_timebase / 1000000ULL);
-- 
2.20.1