From 7efd0da2d17360e1cef91507dbe619db0ee2c691 Mon Sep 17 00:00:00 2001 From: Mischa Jonker Date: Fri, 30 Aug 2013 11:56:25 +0200 Subject: [PATCH] ARC: Fix __udelay calculation Cast usecs to u64, to ensure that the (usecs * 4295 * HZ) multiplication is 64 bit. Initially, the (usecs * 4295 * HZ) part was done as a 32 bit multiplication, with the result casted to 64 bit. This led to some bits falling off, causing a "DMA initialization error" in the stmmac Ethernet driver, due to a premature timeout. Signed-off-by: Mischa Jonker Signed-off-by: Vineet Gupta --- arch/arc/include/asm/delay.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/arch/arc/include/asm/delay.h b/arch/arc/include/asm/delay.h index 442ce5d0f709..43de30256981 100644 --- a/arch/arc/include/asm/delay.h +++ b/arch/arc/include/asm/delay.h @@ -53,11 +53,10 @@ static inline void __udelay(unsigned long usecs) { unsigned long loops; - /* (long long) cast ensures 64 bit MPY - real or emulated + /* (u64) cast ensures 64 bit MPY - real or emulated * HZ * 4295 is pre-evaluated by gcc - hence only 2 mpy ops */ - loops = ((long long)(usecs * 4295 * HZ) * - (long long)(loops_per_jiffy)) >> 32; + loops = ((u64) usecs * 4295 * HZ * loops_per_jiffy) >> 32; __delay(loops); }