[PATCH v2] riscv: Fix udelay in RV32.

[PATCH v2] riscv: Fix udelay in RV32.

[Nick Hu]

In RV32, udelay would delay the wrong cycle. When it shifts right
"UDELAY_SHITFT" 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@andestech.com>
---
 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);
-- 
2.17.0


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Re: [PATCH v2] riscv: Fix udelay in RV32.

[Nick Hu]

On Thu, May 30, 2019 at 02:49:10PM +0800, Nick Chun-Ming Hu(胡峻銘) wrote:
> In RV32, udelay would delay the wrong cycle. When it shifts right
> "UDELAY_SHITFT" 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@andestech.com>
> ---
>  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);
> -- 
> 2.17.0
>

Hi All, I forgot to add "Reviewed-by: Palmer Dabbelt <palmer@sifive.com>".
I will send another patch.

Sorry.

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