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=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,T_DKIMWL_WL_HIGH,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 421FFC072B1 for ; Thu, 30 May 2019 04:12:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19224251A1 for ; Thu, 30 May 2019 04:12:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559189525; bh=W3deDqBV973O01uZLmx5KBYNQkKfVaEZ3DxcfVjdSI0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=VkLqbPQ7NzA9+pFhuj8J3eOzdIlJNCtMAytzQb+voiJ+zeKRyNCtkOKSr5wuPYanr cisIYRrXLlYLKEGcMGsFMF9/2rLYFrlH1ZuiGdGNOp6MaSYSEnaZgCURkVPkvau5tK /Ahs8KKe9y2aj9vw9dAgaFeFlxOo4mjY1YA0dy3U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730354AbfE3EME (ORCPT ); Thu, 30 May 2019 00:12:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:43760 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730784AbfE3DQo (ORCPT ); Wed, 29 May 2019 23:16:44 -0400 Received: from localhost (ip67-88-213-2.z213-88-67.customer.algx.net [67.88.213.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C801D24628; Thu, 30 May 2019 03:16:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559186203; bh=W3deDqBV973O01uZLmx5KBYNQkKfVaEZ3DxcfVjdSI0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lX7Ja1IKI+WR+qvtuTeKLWTFwpwsugk3xBxB0O9ZdXg9KuDQhHF4GEyLthGtyF61r fmdSeXmRRUB+36c5K9asHSwDNRhLW4Ug+u5+UP77+rpjIvAvQGK0btClbcwnbGgX+9 zj4nZXxAGJPcVOoyPwydACVEnpSwVChDLKrZl//8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mariusz Bialonczyk , Jean-Francois Dagenais , Sasha Levin Subject: [PATCH 4.19 089/276] w1: fix the resume command API Date: Wed, 29 May 2019 20:04:07 -0700 Message-Id: <20190530030531.802190504@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190530030523.133519668@linuxfoundation.org> References: <20190530030523.133519668@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ 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