From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id ADC1267A65 for ; Fri, 21 Jan 2005 09:27:54 +1100 (EST) From: Benjamin Herrenschmidt To: Dan Malek In-Reply-To: <93780AB0-696D-11D9-81BE-003065F9B7DC@embeddededge.com> References: <41EC29A8.1040703@mvista.com> <20050118161515.GI28724@smtp.west.cox.net> <93780AB0-696D-11D9-81BE-003065F9B7DC@embeddededge.com> Content-Type: text/plain Date: Fri, 21 Jan 2005 09:27:01 +1100 Message-Id: <1106260021.5387.11.camel@gaston> Mime-Version: 1.0 Cc: Tom Rini , linuxppc-dev list Subject: Re: [RFC] Option to disable mapping genrtc calls to ppc_md calls List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2005-01-18 at 11:25 -0500, Dan Malek wrote: > On Jan 18, 2005, at 11:15 AM, Tom Rini wrote: > > > On Mon, Jan 17, 2005 at 02:10:00PM -0700, Mark A. Greer wrote: > > >> There are 2 reasons to not use the ppc_md.get_rtc_time() et. al. > >> interfaces: > >> 1) They are called before the i2c driver is initialized and even > >> loaded > >> if its a module. > > There are three reasons. You don't want to use an I2c rtc clock at > all in these functions because they get can get called from the > clock interrupt to update the time in the rtc. If it does happen to > work, > it creates long latencies in the timer interrupt. If the i2c requires > an > interrupt, they system will crash or hang. I have the same problem and I think the solution is to fix the clock interrupt to not do this at interrupt time, but delay to a work queue instead. > A system using an I2C RTC should find some way to access the > clock from application space as a standard I2C device and manage > time/clock from the application, not from the kernel. gack ? Ben.