From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mischa Jonker , Vineet Gupta Subject: [ 13/50] ARC: Fix __udelay calculation Date: Wed, 16 Oct 2013 10:44:59 -0700 Message-Id: <20131016174359.974775795@linuxfoundation.org> In-Reply-To: <20131016174358.335646140@linuxfoundation.org> References: <20131016174358.335646140@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mischa Jonker commit 7efd0da2d17360e1cef91507dbe619db0ee2c691 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- arch/arc/include/asm/delay.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/arch/arc/include/asm/delay.h +++ b/arch/arc/include/asm/delay.h @@ -53,11 +53,10 @@ static inline void __udelay(unsigned lon { 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); }