From patchwork Thu Feb 8 13:54:05 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Boris Brezillon X-Patchwork-Id: 870884 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-i2c-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3zcfs53Pnqz9ryT for ; Fri, 9 Feb 2018 00:57:29 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752135AbeBHNyV (ORCPT ); Thu, 8 Feb 2018 08:54:21 -0500 Received: from mail.free-electrons.com ([62.4.15.54]:44557 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752013AbeBHNyS (ORCPT ); Thu, 8 Feb 2018 08:54:18 -0500 Received: by mail.free-electrons.com (Postfix, from userid 110) id B0CE22071B; Thu, 8 Feb 2018 14:54:16 +0100 (CET) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on mail.free-electrons.com X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,SHORTCIRCUIT, URIBL_BLOCKED shortcircuit=ham autolearn=disabled version=3.4.0 Received: from bbrezillon.lan (LStLambert-657-1-97-87.w90-63.abo.wanadoo.fr [90.63.216.87]) by mail.free-electrons.com (Postfix) with ESMTPSA id 4CD56203A5; Thu, 8 Feb 2018 14:54:06 +0100 (CET) From: Boris Brezillon To: Florian Fainelli , Ray Jui , Scott Branden , bcm-kernel-feedback-list@broadcom.com, Stephen Warren , Lee Jones , Eric Anholt , linux-rpi-kernel@lists.infradead.org, Wolfram Sang , linux-i2c@vger.kernel.org Cc: Boris Brezillon , Gerd Hoffmann Subject: [PATCH] i2c: bcm2835: Set up the rising/falling edge delays Date: Thu, 8 Feb 2018 14:54:05 +0100 Message-Id: <20180208135405.25446-1-boris.brezillon@bootlin.com> X-Mailer: git-send-email 2.14.1 Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org From: Eric Anholt We were leaving them in the power on state (or the state the firmware had set up for some client, if we were taking over from them). The boot state was 30 core clocks, when we actually want to sample some time after (to make sure that the new input bit has actually arrived). Signed-off-by: Eric Anholt Signed-off-by: Boris Brezillon Cc: Gerd Hoffmann --- Hello, I'm reviving this patch that has been posted a while ago by Gerd. It fixes EDID retrieval on some (broken?) HDMI displays, but I'm pretty sure it will fix other I2C setup. Note that I also tested the change with a regular I2C device and it worked just fine. Regards, Boris Changes in v2: - rebase on 4.15 --- drivers/i2c/busses/i2c-bcm2835.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c index cd07a69e2e93..44deae78913e 100644 --- a/drivers/i2c/busses/i2c-bcm2835.c +++ b/drivers/i2c/busses/i2c-bcm2835.c @@ -50,6 +50,9 @@ #define BCM2835_I2C_S_CLKT BIT(9) #define BCM2835_I2C_S_LEN BIT(10) /* Fake bit for SW error reporting */ +#define BCM2835_I2C_FEDL_SHIFT 16 +#define BCM2835_I2C_REDL_SHIFT 0 + #define BCM2835_I2C_CDIV_MIN 0x0002 #define BCM2835_I2C_CDIV_MAX 0xFFFE @@ -81,7 +84,7 @@ static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg) static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev) { - u32 divider; + u32 divider, redl, fedl; divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), i2c_dev->bus_clk_rate); @@ -100,6 +103,22 @@ static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev) bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider); + /* + * Number of core clocks to wait after falling edge before + * outputting the next data bit. Note that both FEDL and REDL + * can't be greater than CDIV/2. + */ + fedl = max(divider / 16, 1u); + + /* + * Number of core clocks to wait after rising edge before + * sampling the next incoming data bit. + */ + redl = max(divider / 4, 1u); + + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DEL, + (fedl << BCM2835_I2C_FEDL_SHIFT) | + (redl << BCM2835_I2C_REDL_SHIFT)); return 0; }