From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Sander Subject: Re: Using patch-2.6.33.7.2-rt30 increases latency and CPU usage? Date: Fri, 11 May 2012 20:46:12 +0200 Message-ID: <201205112046.12453.tim01@vlsi.informatik.tu-darmstadt.de> References: Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-15 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-rt-users@vger.kernel.org To: Grant Edwards Return-path: Received: from lnx503.hrz.tu-darmstadt.de ([130.83.156.232]:35541 "EHLO lnx503.hrz.tu-darmstadt.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756373Ab2EKS4A convert rfc822-to-8bit (ORCPT ); Fri, 11 May 2012 14:56:00 -0400 In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org List-ID: Hi > > No, the kernel does not use the FIQ at all. It is free for you to u= se > > as you want. Communication with the FIQ handler can be done using a > > queue based on atomic instructions. Well i think there is some FIQ infrastructure in the kernel and even an= FIQ=20 switch. But the only thing it does is reserving the infrastructure. Not= more=20 not less. I have been toying around with the FIQ interrupt. On our HW (= i.mx35)=20 we still have about 30=B5s interrupt jitter i would like to reduce. But= the=20 Memory for the FIQ was to small and i didn't manage to jump to some c h= andler=20 code within the driver. Does anybody know has some examples how to do t= hat. =46urther since the FIQ is an own mode i thought the only thing one cou= ld use is=20 memory accesses? But when working within the TCM or FIQ memory the jitt= er was=20 very good (it was about 5ns if i can trust my memory). Best regards Tim -- To unsubscribe from this list: send the line "unsubscribe linux-rt-user= s" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html