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=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 59A71C28CC0 for ; Thu, 30 May 2019 03:26:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 123C224A82 for ; Thu, 30 May 2019 03:26:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559186805; bh=zpDVnYjF5VGV7F2+2umof3By86+rf23DqZ1ERK2R1Jw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=TQw5GUbBmiL/Z+jLXXghnjPS7Ym1Omac+7EwatpL+dRojhh6UKbP8otdgKkEXtDfl 0zAzwjSIVDNXyKTV4xdbcryKNwj8RVTdfYWgMNgIr1LfTxbscacx0gT48j6LkYJ613 ieGlb87MCbRBE8iBiu5GwVjslsqRyyP0JSNx55vA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387756AbfE3D0o (ORCPT ); Wed, 29 May 2019 23:26:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:53428 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731771AbfE3DTB (ORCPT ); Wed, 29 May 2019 23:19:01 -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 57D772481E; Thu, 30 May 2019 03:19:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559186340; bh=zpDVnYjF5VGV7F2+2umof3By86+rf23DqZ1ERK2R1Jw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ejxm5bKoVw2lMhQw6tjfVCtPyjYDq36xkwdVHL+b/DOMuZyArIgb7rvPpGmLV8r5C LycG5YT88xqxwqCu5CUmwB0a/N6T7i8zQmopm6CxU/1F+0PHHHpgQ+Y8BfzOBwP/ZW UzSRUXAirLPgkagFWlSQWdGlxadJrqkGMbferaOk= 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 4.14 065/193] w1: fix the resume command API Date: Wed, 29 May 2019 20:05:19 -0700 Message-Id: <20190530030458.472296211@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190530030446.953835040@linuxfoundation.org> References: <20190530030446.953835040@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 d191e1f805799..661551c4ffa25 100644 --- a/drivers/w1/w1_io.c +++ b/drivers/w1/w1_io.c @@ -430,8 +430,7 @@ 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