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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98C8DC433EF for ; Sat, 20 Nov 2021 20:40:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232369AbhKTUnM (ORCPT ); Sat, 20 Nov 2021 15:43:12 -0500 Received: from o1.ptr2625.egauge.net ([167.89.112.53]:44994 "EHLO o1.ptr2625.egauge.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232118AbhKTUnL (ORCPT ); Sat, 20 Nov 2021 15:43:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=egauge.net; h=from:subject:mime-version:to:cc:content-transfer-encoding: content-type; s=sgd; bh=TX0xMK7GUHeUHHgqvA7VUH7LvFvvcMijgypAUYumTPY=; b=Z1+Ak2Grk8XVn8l4I9FytkzWVpeC13ybYSTrD/hou3qiKv0b0afkGGnsl0Tesv8GNEk1 X4BSPVSsYGcDnRxRFKawgfG3OMyVETNzhcZGEHW1IRqEAvyNGEu5jsWIl8fGFoSLIYJgq0 kRe80npfFaTD+m4gxAPbV16Kq1jcJvX9Is0ztWzQlWmydYacBCivNmEf3UI6mxNsk+THds ufm2aKN1/wdmto9yXlcI/a8FRTKM4IdFjmAQ+yW3p07/Ar0O7JAqErkJQpUiNhDErgtfLl Veq2qKc/q2kz+v9wRb1/XICmbORSON/4wv5orSCBXNA831C6h7POWGXZBhH55crg== Received: by filterdrecv-75ff7b5ffb-6sw96 with SMTP id filterdrecv-75ff7b5ffb-6sw96-1-61995BF8-2 2021-11-20 20:35:04.086457464 +0000 UTC m=+6905716.158116308 Received: from pearl.egauge.net (unknown) by geopod-ismtpd-4-0 (SG) with ESMTP id jUsrcopHRv6xe-VWSe-96w Sat, 20 Nov 2021 20:35:03.946 +0000 (UTC) Received: by pearl.egauge.net (Postfix, from userid 1000) id 70380700297; Sat, 20 Nov 2021 13:35:02 -0700 (MST) From: David Mosberger-Tang Subject: [PATCH 1/2] hwmon: (sht4x) Fix EREMOTEIO errors Date: Sat, 20 Nov 2021 20:35:04 +0000 (UTC) Message-Id: <20211120203443.2299276-1-davidm@egauge.net> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-SG-EID: =?us-ascii?Q?+kMxBqj35EdRUKoy8diX1j4AXmPtd302oan+iXZuF8m2Nw4HRW2irNspffT=2Fkh?= =?us-ascii?Q?ET6RJF6+Prbl0h=2FEtF1rRLvMrwroEOU1NSLm17o?= =?us-ascii?Q?cS6DEpPaWkl6Rqrm52602M3yBbGq0vVwQkE7zh4?= =?us-ascii?Q?ubqgrL2OXJIaOvTpEDfPn7frrgoQscFFPdBO5PO?= =?us-ascii?Q?4WAMemFbtzNhvKjR6M8SZU8Pcrk9XDkhdEAE9HD?= =?us-ascii?Q?+eUpuN1E1gOAkgLCJacA5M5iyCwplQs5J7+ZTXF?= =?us-ascii?Q?pBpikyug2cieTvb+1gVpg=3D=3D?= To: Navin Sankar Velliangiri Cc: Jean Delvare , Guenter Roeck , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, David Mosberger-Tang X-Entity-ID: Xg4JGAcGrJFIz2kDG9eoaQ== Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Per datasheet, SHT4x may need up to 8.2ms for a "high repeatability" measurement to complete. Attempting to read the result too early triggers a NAK which then causes an EREMOTEIO error. This behavior has been confirmed with a logic analyzer while running the I2C bus at only 40kHz. The low frequency precludes any signal-integrity issues, which was also confirmed by the absence of any CRC8 errors. In this configuration, a NAK occurred on any read that followed the measurement command within less than 8.2ms. Signed-off-by: David Mosberger-Tang --- drivers/hwmon/sht4x.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c index 09c2a0b06444..3415d7a0e0fc 100644 --- a/drivers/hwmon/sht4x.c +++ b/drivers/hwmon/sht4x.c @@ -23,7 +23,7 @@ /* * I2C command delays (in microseconds) */ -#define SHT4X_MEAS_DELAY 1000 +#define SHT4X_MEAS_DELAY_HPM 8200 /* see t_MEAS,h in datasheet */ #define SHT4X_DELAY_EXTRA 10000 /* @@ -90,7 +90,7 @@ static int sht4x_read_values(struct sht4x_data *data) if (ret < 0) goto unlock; - usleep_range(SHT4X_MEAS_DELAY, SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA); + usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA); ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH); if (ret != SHT4X_RESPONSE_LENGTH) { -- 2.25.1