From patchwork Tue Jan 6 04:09:00 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 5571851 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 37BE19F444 for ; Tue, 6 Jan 2015 04:12:22 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 4B8CB20303 for ; Tue, 6 Jan 2015 04:12:21 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9D2F120274 for ; Tue, 6 Jan 2015 04:12:19 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1Y8LSU-0005YG-4B; Tue, 06 Jan 2015 04:09:30 +0000 Received: from mail-qc0-f182.google.com ([209.85.216.182]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Y8LSQ-0005UA-A0 for linux-arm-kernel@lists.infradead.org; Tue, 06 Jan 2015 04:09:27 +0000 Received: by mail-qc0-f182.google.com with SMTP id r5so16702768qcx.27 for ; Mon, 05 Jan 2015 20:09:03 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; bh=1PB5qvx7RMH1Byk4hmwtQJsHB6Q25rTOzuESQrLpJmw=; b=RTifuSPEkoi9aVAomjind8qOVgmfwNJu7NlpHzQMKHFMlzdkFUTK/DHyeIog+df8y8 gry28ra2B+RmlH5zTMi4KDLLniPrKL2AmT8gKWSv8SnQDI6+9o7vOq1s/yERFIcqhOTJ Xk36ryqWSs9eZkaaW21CZRkZQIcUqsl8Pw02cLyUL2oy14ZJYoIGhJh1CSiMx/XedhR3 qbfGRHgBVAiYcRxVQAh6LVWrmV1d+qJSD+3LbdgQw466qDV66VdNJKBCxeM4LbiBsYVy HqUSQu/8k4nobof9NGWQUm3g8V5Cg/Ks+pEirpxH5nuChfqZJMabRBk0wKV6tSZP5eLa HwPw== X-Gm-Message-State: ALoCoQmBjhMSqzdwxsZw+G8UhLPc0W5DGJoXYIJg0wiE66K8eQtM3c0ZAqDlaDi911kOkpeQceoJ X-Received: by 10.224.45.69 with SMTP id d5mr54911343qaf.56.1420517343497; Mon, 05 Jan 2015 20:09:03 -0800 (PST) Received: from xanadu.home (modemcable142.180-131-66.mc.videotron.ca. [66.131.180.142]) by mx.google.com with ESMTPSA id w9sm36676419qab.18.2015.01.05.20.09.01 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 05 Jan 2015 20:09:02 -0800 (PST) Date: Mon, 5 Jan 2015 23:09:00 -0500 (EST) From: Nicolas Pitre To: Will Deacon Subject: Re: [PATCH] Revert 9fc2105aeaaf56b0cf75296a84702d0f9e64437b to fix pyaudio (and probably more) In-Reply-To: <20150105121126.GA10116@arm.com> Message-ID: References: <20150104190123.GA20153@amd> <20150104201026.GA23427@amd> <20150104203724.GA16372@amd> <20150104212659.GC12302@n2100.arm.linux.org.uk> <20150105121126.GA10116@arm.com> User-Agent: Alpine 2.11 (LFD 23 2013-08-11) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150105_200926_459347_C578363D X-CRM114-Status: GOOD ( 18.86 ) X-Spam-Score: -0.7 (/) Cc: Marc Zyngier , Russell King - ARM Linux , linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Mon, 5 Jan 2015, Will Deacon wrote: > On Mon, Jan 05, 2015 at 04:51:31AM +0000, Nicolas Pitre wrote: > > Because the reported bogomips is orders of magnitude away from the > > traditionally expected value for a given CPU when timer based delays are > > in use, and because lumping bogomips and timer based delay loops is rather > > senseless anyway, let's calibrate bogomips using a CPU loop all the time > > even when timer based delays are available. Timer based delays don't > > need any calibration and /proc/cpuinfo will provide somewhat sensible > > values again. > > > > In practice, calls to __delay() will now always use the CPU based loop. > > Things remain unchanged for udelay() and its derivatives. > > Given that we have a hard limit of 3355 bogomips in our calibration code, > could we not just report that instead? We already have all of the issues I > highlighted above and the systems that are going to be hit by this are the > more recent (more performant) cores that will be approaching this maximum > value anyway. I already replied to the other issues in my previous email. Now here's the bogomips hard limit gone: ----- >8 From: Nicolas Pitre Date: Mon, 5 Jan 2015 22:43:56 -0500 Subject: [PATCH] ARM: loop_udelay: remove bogomips value limitation Now that we don't support ARMv3 anymore, the loop based delay code can convert microsecs into number of loops using a 64-bit multiplication. This allows us to lift the hard limit of 3355 on the bogomips value with loops_per_jiffy that can safely span the full 32-bit range. Signed-off-by: Nicolas Pitre diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h index 7feeb163f5..287c96ad93 100644 --- a/arch/arm/include/asm/delay.h +++ b/arch/arm/include/asm/delay.h @@ -10,8 +10,8 @@ #include /* HZ */ #define MAX_UDELAY_MS 2 -#define UDELAY_MULT ((UL(2199023) * HZ) >> 11) -#define UDELAY_SHIFT 30 +#define UDELAY_MULT UL(2047 * HZ + 483648 * HZ / 1000000) +#define UDELAY_SHIFT 31 #ifndef __ASSEMBLY__ @@ -33,7 +33,7 @@ extern struct arm_delay_ops { * it, it means that you're calling udelay() with an out of range value. * * With currently imposed limits, this means that we support a max delay - * of 2000us. Further limits: HZ<=1000 and bogomips<=3355 + * of 2000us. Further limits: HZ<=1000 */ extern void __bad_udelay(void); diff --git a/arch/arm/lib/delay-loop.S b/arch/arm/lib/delay-loop.S index 518bf6e93f..bcc23c5760 100644 --- a/arch/arm/lib/delay-loop.S +++ b/arch/arm/lib/delay-loop.S @@ -17,7 +17,6 @@ /* * r0 <= 2000 - * lpj <= 0x01ffffff (max. 3355 bogomips) * HZ <= 1000 */ @@ -25,16 +24,11 @@ ENTRY(__loop_udelay) ldr r2, .LC1 mul r0, r2, r0 ENTRY(__loop_const_udelay) @ 0 <= r0 <= 0x7fffff06 - mov r1, #-1 ldr r2, .LC0 - ldr r2, [r2] @ max = 0x01ffffff - add r0, r0, r1, lsr #32-14 - mov r0, r0, lsr #14 @ max = 0x0001ffff - add r2, r2, r1, lsr #32-10 - mov r2, r2, lsr #10 @ max = 0x00007fff - mul r0, r2, r0 @ max = 2^32-1 - add r0, r0, r1, lsr #32-6 - movs r0, r0, lsr #6 + ldr r2, [r2] + umull r1, r0, r2, r0 + adds r1, r1, #0xffffffff + adcs r0, r0, r0 reteq lr /*