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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 608B3C282CE for ; Wed, 22 May 2019 19:45:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 28C4D2089E for ; Wed, 22 May 2019 19:45:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558554340; bh=eHjR7WKf4S/nm5NSKt//euvYzwhQVvsxfSeDGz2iyFo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=otxgShz8JbhsJBjANCZhBAKekTz3vZvLSzsUOfpGlersO7xuIbYcsI9zN37MGhFL8 GctLchdN+FxtdwDBglkr+f26zYZlgMn8El0/LIeuLKqJTW2EXvE7KJySoGD6sxqkrp TjuX+XlqWJXbfMdoDACwo8xJTkt/XKzdmbNTBHJU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387822AbfEVTpi (ORCPT ); Wed, 22 May 2019 15:45:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:50372 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731901AbfEVT1z (ORCPT ); Wed, 22 May 2019 15:27:55 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 23E9920879; Wed, 22 May 2019 19:27:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558553274; bh=eHjR7WKf4S/nm5NSKt//euvYzwhQVvsxfSeDGz2iyFo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GqQbDixfFiuId5yelEOPm2Xa84KaIx8KGGvaQ8PaHE2w+4GpLhNdXo80K3oB9SMAo vEm2j9I6bgsiSjcqvrjABLPpPfoFeTcw2piWt0GJy4ljQU9pD+QgSZNTvi0FK+jtgP tQOUoy0Xt+n46bUDsZA3Ts3PSpq2Z1/iztWSAM1A= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Mariusz Bialonczyk , Jean-Francois Dagenais , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH AUTOSEL 4.19 049/244] w1: fix the resume command API Date: Wed, 22 May 2019 15:23:15 -0400 Message-Id: <20190522192630.24917-49-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190522192630.24917-1-sashal@kernel.org> References: <20190522192630.24917-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mariusz Bialonczyk [ Upstream commit 62909da8aca048ecf9fbd7e484e5100608f40a63 ] >>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 Reviewed-by: Jean-Francois Dagenais Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/w1/w1_io.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c index 0364d3329c526..3516ce6718d94 100644 --- a/drivers/w1/w1_io.c +++ b/drivers/w1/w1_io.c @@ -432,8 +432,7 @@ 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); + w1_write_8(dev, dev->slave_count > 1 ? W1_RESUME_CMD : W1_SKIP_ROM); return 0; } EXPORT_SYMBOL_GPL(w1_reset_resume_command); -- 2.20.1