From patchwork Sat Jan 4 10:55:45 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mauro Carvalho Chehab X-Patchwork-Id: 3433431 Return-Path: X-Original-To: patchwork-linux-media@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 5C0BAC02DD for ; Sat, 4 Jan 2014 13:59:41 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8F8DA20134 for ; Sat, 4 Jan 2014 13:59:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 510A520136 for ; Sat, 4 Jan 2014 13:59:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754189AbaADN7X (ORCPT ); Sat, 4 Jan 2014 08:59:23 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:43694 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753210AbaADN7R (ORCPT ); Sat, 4 Jan 2014 08:59:17 -0500 Received: from [177.143.150.208] (helo=smtp.w2.samsung.com) by bombadil.infradead.org with esmtpsa (Exim 4.80.1 #2 (Red Hat Linux)) id 1VzRkw-00013r-Kr; Sat, 04 Jan 2014 13:59:15 +0000 Received: from mchehab by smtp.w2.samsung.com with local (Exim 4.80.1) (envelope-from ) id 1VzOtV-0003kh-N5; Sat, 04 Jan 2014 08:55:53 -0200 From: Mauro Carvalho Chehab Cc: Mauro Carvalho Chehab , Linux Media Mailing List , Mauro Carvalho Chehab Subject: [PATCH v4 16/22] [media] em28xx: use a better value for I2C timeouts Date: Sat, 4 Jan 2014 08:55:45 -0200 Message-Id: <1388832951-11195-17-git-send-email-m.chehab@samsung.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1388832951-11195-1-git-send-email-m.chehab@samsung.com> References: <1388832951-11195-1-git-send-email-m.chehab@samsung.com> To: unlisted-recipients:; (no To-header on input) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org X-Spam-Status: No, score=-7.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In the lack of a better spec, let's assume the timeout values compatible with SMBus spec: http://smbus.org/specs/smbus110.pdf at chapter 8 - Electrical Characteristics of SMBus devices Ok, SMBus is a subset of I2C, and not all devices will be following it, but the timeout value before this patch was not even following the spec. So, while we don't have a better guess for it, use 35 + 1 ms as the timeout. Signed-off-by: Mauro Carvalho Chehab --- drivers/media/usb/em28xx/em28xx.h | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h index db47c2236ca4..9af19332b0f1 100644 --- a/drivers/media/usb/em28xx/em28xx.h +++ b/drivers/media/usb/em28xx/em28xx.h @@ -183,8 +183,21 @@ #define EM28XX_INTERLACED_DEFAULT 1 -/* time in msecs to wait for i2c xfers to finish */ -#define EM2800_I2C_XFER_TIMEOUT 20 +/* + * Time in msecs to wait for i2c xfers to finish. + * 35ms is the maximum time a SMBUS device could wait when + * clock stretching is used. As the transfer itself will take + * some time to happen, set it to 35 ms. + * + * Ok, I2C doesn't specify any limit. So, eventually, we may need + * to increase this timeout. + * + * FIXME: this assumes that an I2C message is not longer than 1ms. + * This is actually dependent on the I2C bus speed, although most + * devices use a 100kHz clock. So, this assumtion is true most of + * the time. + */ +#define EM2800_I2C_XFER_TIMEOUT 36 /* time in msecs to wait for AC97 xfers to finish */ #define EM2800_AC97_XFER_TIMEOUT 100