From patchwork Wed Apr 27 18:11:54 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Zimmermann X-Patchwork-Id: 615762 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3qw7Nh3CCQz9sBG for ; Thu, 28 Apr 2016 04:12:52 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=googlemail.com header.i=@googlemail.com header.b=KoDNZnb0; dkim-atps=neutral Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752526AbcD0SMu (ORCPT ); Wed, 27 Apr 2016 14:12:50 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:34642 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753505AbcD0SMt (ORCPT ); Wed, 27 Apr 2016 14:12:49 -0400 Received: by mail-wm0-f68.google.com with SMTP id n129so6238581wmn.1; Wed, 27 Apr 2016 11:12:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id; bh=gpOQ9V1zIIdPIE8BbrU8oIUww+buSzf8Yf9ikDizCBA=; b=KoDNZnb0sXyJB3xqE+ADYTedmWZA1eHXp945lpncom4IKixd/HrdKAJ+sgLfqj6wEB mDFK9+uCa3jqk/pocXRqWxY3uUlUcaS0HJ1p/6uMbF8h/D7I0hOrQDt0p0vVdrQwaikF JINM11Bn08RNyomT81pFYaB2DDOPB7cy9aRNhDg2iVzClIYnW6MnSBXecB1xOa/345EH CoInXFrDDzffjx2Zda14iGOEyoeoSU4LurXCtLosC+gAFhKt8ESwFcwuTsCoGDZyyIpS q0y/LEFgPrTawVVSbtmr6BYRcU7I+JnxLZDObU0n+q+9IPtrAGQ+ohBKk05HTGskOPwk X/cw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id; bh=gpOQ9V1zIIdPIE8BbrU8oIUww+buSzf8Yf9ikDizCBA=; b=f+DxcUPmRlQVoTc5GneFGsbhzkpjRny1ZIWd5R5/D76HzBAHYvjNhFWhjUsGQj6XcQ JNN1NBdm1/SF2rSPfDfKiYwWrFuuTGvfXjRi8/MuLSmX7VGzEI1sRAHiqYCT0P7rz0FQ 5HtrqAUPmtLhyIr+ug55uz5wFpr1IwTJR4xxLMIVa2XZjLt9m/5v7jjeh5E0MJoV9gAF t6zoEDDIj+6eCKkr7mLrikx3dAun8tc4x+rdLuzw6ZHkbTn5BZa8dqFcCzwHn3W2uZR3 17DihUSv9TJ7S5Zr+3KPRwQOGduxALtJHeRYtI+LSXS7wlCLagiSh1qZvwxp0bo3mESQ 18cw== X-Gm-Message-State: AOPr4FUx1d2pIVHGjWj3rC67hMewXedZwlrh+OMqNX1/bks6UsSfXL9TW6mIqxvKmDwppQ== X-Received: by 10.28.18.10 with SMTP id 10mr28011595wms.0.1461780767300; Wed, 27 Apr 2016 11:12:47 -0700 (PDT) Received: from barney.fritz.box (dslb-088-068-239-045.088.068.pools.vodafone-ip.de. [88.68.239.45]) by smtp.gmail.com with ESMTPSA id ki9sm5286884wjb.37.2016.04.27.11.12.46 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 27 Apr 2016 11:12:46 -0700 (PDT) From: Thomas Zimmermann To: wsa@the-dreams.de Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Zimmermann Subject: [PATCH] i2c: Raise SDA for each received bit, if necessary Date: Wed, 27 Apr 2016 20:11:54 +0200 Message-Id: <1461780714-20378-1-git-send-email-tdz@users.sourceforge.net> X-Mailer: git-send-email 2.1.4 Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org Some I2C adapters don't raise SDA by themselves when sending a bit. This behavior can be seen with the DDC channel of SiS 300 graphics cards. This patch adds the flag |set_sdahi| to |struct i2c_algo_bit_data|. With the flags set to true, the I2C bit algo will raise SDA before reading each bit from the bus. With the flag set to false, the bit algo will keep its current behavior of raising SDA only once before receiving a full byte. The flag also ensures that |acknak| is always called with SDA raised. Signed-off-by: Thomas Zimmermann --- drivers/i2c/algos/i2c-algo-bit.c | 2 ++ include/linux/i2c-algo-bit.h | 5 +++++ 2 files changed, 7 insertions(+) diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c index 9d233bb..aa8cf33 100644 --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -224,6 +224,8 @@ static int i2c_inb(struct i2c_adapter *i2c_adap) indata |= 0x01; setscl(adap, 0); udelay(i == 7 ? adap->udelay / 2 : adap->udelay); + if (adap->set_sdahi) + sdahi(adap); } /* assert: scl is low */ return indata; diff --git a/include/linux/i2c-algo-bit.h b/include/linux/i2c-algo-bit.h index 63904ba..e9f0a59 100644 --- a/include/linux/i2c-algo-bit.h +++ b/include/linux/i2c-algo-bit.h @@ -46,6 +46,11 @@ struct i2c_algo_bit_data { minimum 5 us for standard-mode I2C and SMBus, maximum 50 us for SMBus */ int timeout; /* in jiffies */ + + /* Some adapters do not raise SDA by themselves when sending. Set + * this flag to raise SDA before reading each bit. + */ + bool set_sdahi; }; int i2c_bit_add_bus(struct i2c_adapter *);