From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0917C10F00 for ; Mon, 18 Mar 2019 09:28:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7FE321734 for ; Mon, 18 Mar 2019 09:28:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728003AbfCRJ2G (ORCPT ); Mon, 18 Mar 2019 05:28:06 -0400 Received: from skyboo.net ([94.40.87.198]:39094 "EHLO skyboo.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727961AbfCRJ2B (ORCPT ); Mon, 18 Mar 2019 05:28:01 -0400 Received: from manio by skyboo.net with local (Exim 4.91) (envelope-from ) id 1h5oYn-0002Ie-Gb; Mon, 18 Mar 2019 10:27:57 +0100 From: Mariusz Bialonczyk To: linux-kernel@vger.kernel.org, Evgeniy Polyakov , Greg Kroah-Hartman , Jean-Francois Dagenais Cc: Mariusz Bialonczyk Date: Mon, 18 Mar 2019 10:27:37 +0100 Message-Id: <20190318092737.8170-3-manio@skyboo.net> X-Mailer: git-send-email 2.19.0.rc1 In-Reply-To: <20190318092737.8170-1-manio@skyboo.net> References: <20190318092737.8170-1-manio@skyboo.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: X-SA-Exim-Rcpt-To: linux-kernel@vger.kernel.org, zbr@ioremap.net, greg@kroah.com, jeff.dagenais@gmail.com, manio@skyboo.net X-SA-Exim-Mail-From: manio@skyboo.net Subject: [PATCH 2/2] w1: fix the resume command API X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: Yes (on skyboo.net) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >From the DS2408 datasheet [1]: "Resume Command function checks the status of the RC flag and, if it is set, directly transfers control to the control functions, similar to a Skip ROM command. The only way to set the RC flag is through successfully executing the Match ROM, Search ROM, Conditional Search ROM, or Overdrive-Match ROM command" The function currently works perfectly fine in a multidrop bus, but when we have only a single slave connected, then only a Skip ROM is used and Match ROM is not called at all. This is leading to problems e.g. with single one DS2408 connected, as the Resume Command is not working properly and the device is responding with failing results after the Resume Command. This commit is fixing this by using a Skip ROM instead in those cases. The bandwidth / performance advantage is exactly the same. Refs: [1] https://datasheets.maximintegrated.com/en/ds/DS2408.pdf Signed-off-by: Mariusz Bialonczyk Cc: Jean-Francois Dagenais --- drivers/w1/w1_io.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c index 0364d3329c52..4697136b9027 100644 --- a/drivers/w1/w1_io.c +++ b/drivers/w1/w1_io.c @@ -432,8 +432,15 @@ int w1_reset_resume_command(struct w1_master *dev) if (w1_reset_bus(dev)) return -1; - /* This will make only the last matched slave perform a skip ROM. */ - w1_write_8(dev, W1_RESUME_CMD); + if (dev->slave_count == 1) { + /* Resume Command has to be preceeded with e.g. Match ROM which is + * not happening on single-slave buses, just do a Skip ROM instead + */ + w1_write_8(dev, W1_SKIP_ROM); + } else { + /* This will make only the last matched slave perform a skip ROM. */ + w1_write_8(dev, W1_RESUME_CMD); + } return 0; } EXPORT_SYMBOL_GPL(w1_reset_resume_command); -- 2.19.0.rc1