From patchwork Wed Oct 5 22:56:11 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Russell King (Oracle)" X-Patchwork-Id: 9363551 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 14A57607D6 for ; Wed, 5 Oct 2016 22:58:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E811528CC6 for ; Wed, 5 Oct 2016 22:58:21 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DB70628D21; Wed, 5 Oct 2016 22:58:21 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id AC7A428CC6 for ; Wed, 5 Oct 2016 22:58:20 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1brv7G-0007Rc-5q; Wed, 05 Oct 2016 22:56:46 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:3201:214:fdff:fe10:1be6]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1brv7A-0007Mw-Ud for linux-arm-kernel@lists.infradead.org; Wed, 05 Oct 2016 22:56:43 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2014; h=Date:Sender:Message-Id:Content-Type:Content-Transfer-Encoding:MIME-Version:Subject:Cc:To:From; bh=IXm6bxyvemOb5KRNDbtSeSkw+5u4mJMV5IEQV1nyVE0=; b=jGcxlwwGnq/iDi7zw0jL3dka4eLWRN0x3DlMDaZs3QNlEGSJgVLmQqmRsbzDwTQJYil+6KkVqBmwXWbdfB2WoRCcBVwr9m+mHnYSnOcCfmX5040XgvgWPsg5knor6TDqH42475hCl4tuckdf5ocG5D3rZ1HcvcfeT2VmJAC8V5E=; Received: from e0022681537dd.dyn.armlinux.org.uk ([fd8f:7570:feb6:1:222:68ff:fe15:37dd]:40784 helo=rmk-PC.armlinux.org.uk) by pandora.armlinux.org.uk with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1brv6i-0005Qu-3t; Wed, 05 Oct 2016 23:56:12 +0100 Received: from rmk by rmk-PC.armlinux.org.uk with local (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1brv6h-0003j7-7J; Wed, 05 Oct 2016 23:56:11 +0100 From: Russell King To: Nicolas Pitre Subject: [PATCH] ARM: fix delays MIME-Version: 1.0 Content-Disposition: inline Message-Id: Date: Wed, 05 Oct 2016 23:56:11 +0100 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20161005_155641_984991_437DDE25 X-CRM114-Status: GOOD ( 11.61 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Commit 215e362dafed ("ARM: 8306/1: loop_udelay: remove bogomips value limitation") tried to increase the bogomips limitation, but in doing so messed up udelay such that it always gives about a 5% error in the delay, even if we use a timer. The calculation is: loops = UDELAY_MULT * us_delay * ticks_per_jiffy >> UDELAY_SHIFT Originally, UDELAY_MULT was ((UL(2199023) * HZ) >> 11) and UDELAY_SHIFT 30. Assuming HZ=100, us_delay of 1000 and ticks_per_jiffy of 1660000 (eg, 166MHz timer, 1ms delay) this would calculate: ((UL(2199023) * HZ) >> 11) * 1000 * 1660000 >> 30 => 165999 With the new values of 2047 * HZ + 483648 * HZ / 1000000 and 31, we get: (2047 * HZ + 483648 * HZ / 1000000) * 1000 * 1660000 >> 31 => 158269 which is incorrect. This is due to a typo - correcting it gives: (2147 * HZ + 483648 * HZ / 1000000) * 1000 * 1660000 >> 31 => 165999 i.o.w, the original value. Fixes: 215e362dafed ("ARM: 8306/1: loop_udelay: remove bogomips value limitation") Cc: Signed-off-by: Russell King Reviewed-by: Nicolas Pitre --- arch/arm/include/asm/delay.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h index b7a428154355..b1ce037e4380 100644 --- a/arch/arm/include/asm/delay.h +++ b/arch/arm/include/asm/delay.h @@ -10,7 +10,7 @@ #include /* HZ */ #define MAX_UDELAY_MS 2 -#define UDELAY_MULT UL(2047 * HZ + 483648 * HZ / 1000000) +#define UDELAY_MULT UL(2147 * HZ + 483648 * HZ / 1000000) #define UDELAY_SHIFT 31 #ifndef __ASSEMBLY__