From patchwork Wed Nov 13 09:21:33 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Geert Uytterhoeven X-Patchwork-Id: 11241465 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2524D17E6 for ; Wed, 13 Nov 2019 09:22:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 10ED72245B for ; Wed, 13 Nov 2019 09:22:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727323AbfKMJVs (ORCPT ); Wed, 13 Nov 2019 04:21:48 -0500 Received: from andre.telenet-ops.be ([195.130.132.53]:51886 "EHLO andre.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726613AbfKMJVq (ORCPT ); Wed, 13 Nov 2019 04:21:46 -0500 Received: from ramsan ([84.195.182.253]) by andre.telenet-ops.be with bizsmtp id RMMk2100G5USYZQ01MMkEE; Wed, 13 Nov 2019 10:21:44 +0100 Received: from rox.of.borg ([192.168.97.57]) by ramsan with esmtp (Exim 4.90_1) (envelope-from ) id 1iUoqO-0001qZ-7m; Wed, 13 Nov 2019 10:21:44 +0100 Received: from geert by rox.of.borg with local (Exim 4.90_1) (envelope-from ) id 1iUoqO-0006Bh-5R; Wed, 13 Nov 2019 10:21:44 +0100 From: Geert Uytterhoeven To: Jacopo Mondi , Jonathan Cameron , Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler Cc: Wolfram Sang , linux-iio@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH] iio: adc: max9611: Fix too short conversion time delay Date: Wed, 13 Nov 2019 10:21:33 +0100 Message-Id: <20191113092133.23723-1-geert+renesas@glider.be> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org As of commit b9ddd5091160793e ("iio: adc: max9611: Fix temperature reading in probe"), max9611 initialization sometimes fails on the Salvator-X(S) development board with: max9611 4-007f: Invalid value received from ADC 0x8000: aborting max9611: probe of 4-007f failed with error -5 The max9611 driver tests communications with the chip by reading the die temperature during the probe function, which returns an invalid value. According to the datasheet, the typical ADC conversion time is 2 ms, but no minimum or maximum values are provided. However, the driver assumes a 1 ms conversion time. Usually the usleep_range() call returns after more than 1.8 ms, hence it succeeds. When it returns earlier, the data register may be read too early, and the previous measurement value will be returned. After boot, this is the temperature POR (power-on reset) value, causing the failure above. Fix this by increasing the delay from 1000-2000 µs to 2000-2200 µs. Note that this issue has always been present, but it was exposed by the aformentioned commit. Fixes: 69780a3bbc0b1e7e ("iio: adc: Add Maxim max9611 ADC driver") Signed-off-by: Geert Uytterhoeven Reviewed-by: Jacopo Mondi --- This problem was exposed in v5.3. After this patch, probing of the two max9611 sensors succeeded during ca. 3000 boot cycles on Salvator-X(S) boards, equipped with various R-Car H3/M3-W/M3-N SoCs. --- drivers/iio/adc/max9611.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/iio/adc/max9611.c b/drivers/iio/adc/max9611.c index da073d72f649f829..b0755f25356d700d 100644 --- a/drivers/iio/adc/max9611.c +++ b/drivers/iio/adc/max9611.c @@ -89,6 +89,11 @@ #define MAX9611_TEMP_SCALE_NUM 1000000 #define MAX9611_TEMP_SCALE_DIV 2083 +/* + * Conversion time is 2 ms (typically) + */ +#define MAX9611_CONV_TIME_US_RANGE 2000, 2200 + struct max9611_dev { struct device *dev; struct i2c_client *i2c_client; @@ -238,9 +243,9 @@ static int max9611_read_single(struct max9611_dev *max9611, /* * need a delay here to make register configuration - * stabilize. 1 msec at least, from empirical testing. + * stabilize. */ - usleep_range(1000, 2000); + usleep_range(MAX9611_CONV_TIME_US_RANGE); ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr); if (ret < 0) { @@ -507,7 +512,7 @@ static int max9611_init(struct max9611_dev *max9611) MAX9611_REG_CTRL2, 0); return ret; } - usleep_range(1000, 2000); + usleep_range(MAX9611_CONV_TIME_US_RANGE); return 0; }