From patchwork Sun Mar 12 16:03:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lars-Peter Clausen X-Patchwork-Id: 13171532 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 DA03BC6FA99 for ; Sun, 12 Mar 2023 16:03:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229738AbjCLQDj (ORCPT ); Sun, 12 Mar 2023 12:03:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53764 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229552AbjCLQDi (ORCPT ); Sun, 12 Mar 2023 12:03:38 -0400 Received: from www381.your-server.de (www381.your-server.de [78.46.137.84]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B74223A5A for ; Sun, 12 Mar 2023 09:03:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=metafoo.de; s=default2002; h=Content-Transfer-Encoding:MIME-Version:Message-Id:Date: Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References; bh=6nqeLRJOZuJTNr2l3hjsujbhzhC8YFtOPgz9TdRbxyg=; b=H9yrTTNRaC/w5VH/1GgFc50tQL nTldXfDCdzqlC7H6z6KhV9YTKXX1LeCLVGukzl5rUrk6v692cxiKW9o8wp0U5tjV79w92UiU/aKM1 LZwKQdv6Am+NduHy3US4ChMjq0b+e3GbBYWHzmbaAga2DqWVmDulyL9pF0Us/lksuLL1Woreszqn9 U9iDE4W3sG2mdR7+hwvgdXa+12pr2SQLxfNTdpBiwfVJ1U0SGfDAMM3uvlaOtmtg/GiOcRHrCirux x7xd8a+16EunrGuwqECGXmKlFWBv0lwfVkHQoFEyjKLK3vdKvSOOLM6JkWYQqsuO3cDHYCrOjpotb SRdgJbpg==; Received: from sslproxy05.your-server.de ([78.46.172.2]) by www381.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1pbOAY-0009lh-Hh; Sun, 12 Mar 2023 17:03:34 +0100 Received: from [2604:5500:c0e5:eb00:da5e:d3ff:feff:933b] (helo=lars-desktop.lan) by sslproxy05.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1pbOAY-000AbK-2h; Sun, 12 Mar 2023 17:03:34 +0100 From: Lars-Peter Clausen To: Guenter Roeck , Jean Delvare Cc: linux-hwmon@vger.kernel.org, Lars-Peter Clausen Subject: [PATCH] hwmon: (ucd90320) Add minimum delay between bus accesses Date: Sun, 12 Mar 2023 09:03:12 -0700 Message-Id: <20230312160312.2227405-1-lars@metafoo.de> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-Authenticated-Sender: lars@metafoo.de X-Virus-Scanned: Clear (ClamAV 0.103.8/26839/Sun Mar 12 09:22:48 2023) Precedence: bulk List-ID: X-Mailing-List: linux-hwmon@vger.kernel.org When probing the ucd90320 access to some of the registers randomly fails. Sometimes it NACKs a transfer, sometimes it returns just random data and the PEC check fails. Experimentation shows that this seems to be triggered by a register access directly back to back with a previous register write. Experimentation also shows that inserting a small delay after register writes makes the issue go away. Use a similar solution to what the max15301 driver does to solve the same problem. Create a custom set of bus read and write functions that make sure that the delay is added. Signed-off-by: Lars-Peter Clausen --- drivers/hwmon/pmbus/ucd9000.c | 75 +++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c index 75fc770c9e40..3daaf2237832 100644 --- a/drivers/hwmon/pmbus/ucd9000.c +++ b/drivers/hwmon/pmbus/ucd9000.c @@ -7,6 +7,7 @@ */ #include +#include #include #include #include @@ -16,6 +17,7 @@ #include #include #include +#include #include "pmbus.h" enum chips { ucd9000, ucd90120, ucd90124, ucd90160, ucd90320, ucd9090, @@ -65,6 +67,7 @@ struct ucd9000_data { struct gpio_chip gpio; #endif struct dentry *debugfs; + ktime_t write_time; }; #define to_ucd9000_data(_info) container_of(_info, struct ucd9000_data, info) @@ -73,6 +76,73 @@ struct ucd9000_debugfs_entry { u8 index; }; +/* + * It has been observed that the UCD90320 randomly fails register access when + * doing another access right on the back of a register write. To mitigate this + * make sure that there is a minimum delay between a write access and the + * following access. The 250us is based on experimental data. At a delay of + * 200us the issue seems to go away. Add a bit of extra margin to allow for + * system to system differences. + */ +#define UCD90320_WAIT_DELAY_US 250 + +static inline void ucd90320_wait(const struct ucd9000_data *data) +{ + s64 delta = ktime_us_delta(ktime_get(), data->write_time); + + if (delta < UCD90320_WAIT_DELAY_US) + udelay(UCD90320_WAIT_DELAY_US - delta); +} + +static int ucd90320_read_word_data(struct i2c_client *client, int page, + int phase, int reg) +{ + const struct pmbus_driver_info *info = pmbus_get_driver_info(client); + struct ucd9000_data *data = to_ucd9000_data(info); + + if (reg >= PMBUS_VIRT_BASE) + return -ENXIO; + + ucd90320_wait(data); + return pmbus_read_word_data(client, page, phase, reg); +} + +static int ucd90320_read_byte_data(struct i2c_client *client, int page, int reg) +{ + const struct pmbus_driver_info *info = pmbus_get_driver_info(client); + struct ucd9000_data *data = to_ucd9000_data(info); + + ucd90320_wait(data); + return pmbus_read_byte_data(client, page, reg); +} + +static int ucd90320_write_word_data(struct i2c_client *client, int page, + int reg, u16 word) +{ + const struct pmbus_driver_info *info = pmbus_get_driver_info(client); + struct ucd9000_data *data = to_ucd9000_data(info); + int ret; + + ucd90320_wait(data); + ret = pmbus_write_word_data(client, page, reg, word); + data->write_time = ktime_get(); + + return ret; +} + +static int ucd90320_write_byte(struct i2c_client *client, int page, u8 value) +{ + const struct pmbus_driver_info *info = pmbus_get_driver_info(client); + struct ucd9000_data *data = to_ucd9000_data(info); + int ret; + + ucd90320_wait(data); + ret = pmbus_write_byte(client, page, value); + data->write_time = ktime_get(); + + return ret; +} + static int ucd9000_get_fan_config(struct i2c_client *client, int fan) { int fan_config = 0; @@ -598,6 +668,11 @@ static int ucd9000_probe(struct i2c_client *client) info->read_byte_data = ucd9000_read_byte_data; info->func[0] |= PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_FAN12 | PMBUS_HAVE_FAN34 | PMBUS_HAVE_STATUS_FAN34; + } else if (mid->driver_data == ucd90320) { + info->read_byte_data = ucd90320_read_byte_data; + info->read_word_data = ucd90320_read_word_data; + info->write_byte = ucd90320_write_byte; + info->write_word_data = ucd90320_write_word_data; } ucd9000_probe_gpio(client, mid, data);