Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762100AbYGaCxw (ORCPT ); Wed, 30 Jul 2008 22:53:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760426AbYGaCty (ORCPT ); Wed, 30 Jul 2008 22:49:54 -0400 Received: from SpacedOut.fries.net ([67.64.210.234]:60564 "EHLO SpacedOut.fries.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755911AbYGaCtx (ORCPT ); Wed, 30 Jul 2008 22:49:53 -0400 Date: Wed, 30 Jul 2008 21:49:47 -0500 From: David Fries To: Andrew Morton Cc: Evgeniy Polyakov , linux-kernel@vger.kernel.org Subject: [PATCH 17/30] W1: w1_io.c reset comments and msleep Message-ID: <20080731024947.GR12181@spacedout.fries.net> References: <20080729020433.GA24424@spacedout.fries.net> <20080729161356.2de456fb.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080729161356.2de456fb.akpm@linux-foundation.org> User-Agent: Mutt/1.5.4i X-Greylist: Sender is SPF-compliant, not delayed by milter-greylist-3.0 (SpacedOut.fries.net [127.0.0.1]); Wed, 30 Jul 2008 21:49:48 -0500 (CDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1891 Lines: 50 w1_reset_bus, added some comments about the timing and switched to msleep for the later delay. I don't have the hardware to test the sleep after reset change. The one wire doesn't have a timing requirement between commands so it is fine. I do have the USB hardware and it would be in big trouble with 10ms interrupt transfers to find that the reset completed. Signed-off-by: David Fries Signed-off-by: Evgeniy Polyakov --- drivers/w1/w1_io.c | 14 +++++++++++++- 1 files changed, 13 insertions(+), 1 deletions(-) diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c index 97b338a..f4f82f1 100644 --- a/drivers/w1/w1_io.c +++ b/drivers/w1/w1_io.c @@ -293,12 +293,24 @@ int w1_reset_bus(struct w1_master *dev) result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1; else { dev->bus_master->write_bit(dev->bus_master->data, 0); + /* minimum 480, max ? us + * be nice and sleep, except 18b20 spec lists 960us maximum, + * so until we can sleep with microsecond accuracy, spin. + * Feel free to come up with some other way to give up the + * cpu for such a short amount of time AND get it back in + * the maximum amount of time. + */ w1_delay(480); dev->bus_master->write_bit(dev->bus_master->data, 1); w1_delay(70); result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1; - w1_delay(410); + /* minmum 70 (above) + 410 = 480 us + * There aren't any timing requirements between a reset and + * the following transactions. Sleeping is safe here. + */ + /* w1_delay(410); min required time */ + msleep(1); } return result; -- 1.4.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/