[PATCH] riscv: delay: use do_div() instead of __udivdi3()

[PATCH] riscv: delay: use do_div() instead of __udivdi3()

[Paul Walmsley]

In preparation for removing __udivdi3() from the RISC-V
architecture-specific files, convert its one user to use do_div().
This avoids breaking the RV32 build after __udivdi3() is removed.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
---
 arch/riscv/lib/delay.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/lib/delay.c b/arch/riscv/lib/delay.c
index 87ff89e88f2c..8c686934e0f6 100644
--- a/arch/riscv/lib/delay.c
+++ b/arch/riscv/lib/delay.c
@@ -81,9 +81,14 @@ EXPORT_SYMBOL(__delay);
 void udelay(unsigned long usecs)
 {
 	u64 ucycles = (u64)usecs * lpj_fine * UDELAY_MULT;
+	u64 n;
+	u32 rem;
 
 	if (unlikely(usecs > MAX_UDELAY_US)) {
-		__delay((u64)usecs * riscv_timebase / 1000000ULL);
+		n = (u64)usecs * riscv_timebase;
+		rem = do_div(n, 1000000);
+
+		__delay(n);
 		return;
 	}
 
-- 
2.22.0

Re: [PATCH] riscv: delay: use do_div() instead of __udivdi3()

[Christoph Hellwig]

> diff --git a/arch/riscv/lib/delay.c b/arch/riscv/lib/delay.c
> index 87ff89e88f2c..8c686934e0f6 100644
> --- a/arch/riscv/lib/delay.c
> +++ b/arch/riscv/lib/delay.c
> @@ -81,9 +81,14 @@ EXPORT_SYMBOL(__delay);
>  void udelay(unsigned long usecs)
>  {
>  	u64 ucycles = (u64)usecs * lpj_fine * UDELAY_MULT;
> +	u64 n;
> +	u32 rem;
>  
>  	if (unlikely(usecs > MAX_UDELAY_US)) {
> -		__delay((u64)usecs * riscv_timebase / 1000000ULL);
> +		n = (u64)usecs * riscv_timebase;
> +		rem = do_div(n, 1000000);
> +
> +		__delay(n);
>  		return;

A few comments on the variable usage:

I think you really want a variable of type u64 that contains the usecs
value instead of casting it three times.

n and rem can be easily declared inside the branch.