From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: omap3 cpuidle interrupt latency Date: Mon, 02 Mar 2009 11:46:17 -0800 Message-ID: <873advaet2.fsf@deeprootsystems.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from rv-out-0506.google.com ([209.85.198.226]:20663 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754088AbZCBTqW (ORCPT ); Mon, 2 Mar 2009 14:46:22 -0500 Received: by rv-out-0506.google.com with SMTP id g9so5456915rvb.5 for ; Mon, 02 Mar 2009 11:46:20 -0800 (PST) In-Reply-To: (Sanjeev Premi's message of "Sat\, 28 Feb 2009 23\:22\:48 +0530") Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: "Premi, Sanjeev" Cc: "linux-omap@vger.kernel.org" "Premi, Sanjeev" writes: > I have noticed large interrupt latency when the cpuidle is enabled. > e.g. response time for ping goes from avg 10-20ms to 800-1000ms. > (I am at HEAD of the 'pm' branch) Is it interrupt latency in general you are measuring? or just the interrupt latency for the smc network driver. I think what you are seeing is the result of the SMC IRQ not being configured as a wakeup source, thus a network interrupt will not wake the system, but you end up waiting for the next idle timer until the system wakes and handles the network interrupt. By default, I don't believe the GPIO interrupt used by the smc is configured as a wakeup source. Have you configured that GPIO as a wakeup source? Kevin > The IRQs and FIQs are disabled at the beginning of the function > omap3_enter_idle() but WFI is executed much later in _omap_sram_idle(). > In between, there is only one check for pending IRQs - omap_irq_pending() > > If any interrupt occurs beyond this point is it considered by the WFI? > > To reduce this latency, I am planning to do either/both of thse: > - Add more checks for pending IRQs > - Reduce the time for which the IRQs and FIQs are disabled > > Benefits will depend upon the behavior of WFI. > > Best regards, > Sanjeev > > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html