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 X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66D04C43460 for ; Fri, 9 Apr 2021 03:15:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 47945610F7 for ; Fri, 9 Apr 2021 03:15:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233049AbhDIDPT (ORCPT ); Thu, 8 Apr 2021 23:15:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233356AbhDIDPN (ORCPT ); Thu, 8 Apr 2021 23:15:13 -0400 Received: from mail-qk1-x72f.google.com (mail-qk1-x72f.google.com [IPv6:2607:f8b0:4864:20::72f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8291EC061760; Thu, 8 Apr 2021 20:15:01 -0700 (PDT) Received: by mail-qk1-x72f.google.com with SMTP id g20so4572263qkk.1; Thu, 08 Apr 2021 20:15:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=UY8w9En2oM59QlKUDijmqzHbmHKyfoguHERW7I1WkUY=; b=IlhuPAD9jW/c28H/N32t7i9j6/yEaGz4aP8UVyt3EkGMOpVCyUv47V6GCPzGWJJo9q wyTcvf0hOxfjyGP/k/B2QNacDqIKj26L5mNS9JHs+a2ShmdEDVdTsQ0iR2Ldooz/793X yg2f1w8v5PCMmofjxcKI708MzzZDKo1lNHqEYWSYN1+M6wIE+qJZeo2WW6uV5c2BYY8F QTZDhAhrf3Wze2ZIt6EHih7pXX//NdZad1kKUjk7Iuw+M76K4wqTHZmq9aju1nJfvoAa WHheWKNe4UC5cT1KQrviJEDYJdu1hIFy/ext8Bb4XIcAjqEZm8G+Gh1f29RLw+NAJMKs Gslg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=UY8w9En2oM59QlKUDijmqzHbmHKyfoguHERW7I1WkUY=; b=RqBX5LLKoUzIcbyNy2KraZ7nPuThSejsuOIHGJXSlRlEqoyZ/yCmpZDV09R4lQyZM+ uWj1mxfilGbVzB5My/EFWD6loP4fjch5qR72gqgUYSAZQRmbhmHQHEwzgIHrzYz235vj 3tCqPgyG19hmYJ3mamf1AIo7kTJ85gRP4AApA9JPApEsL+0pZ69lER0hxIYWiTkcxVT1 QHtXm+VZfAbpBquYkj31EHinYq2n0Y9fGKp9ocTCo7w9hVIpG7+unnxkBhuoQMcV5KUF y0uYm5qhf2quMuuTS0wtgmjVYprpJmnNaSkLy7fCzZmPpy81yy7WKxozm2Q0kGQsnB8L uBog== X-Gm-Message-State: AOAM532PTDgULIqGTdxO1VDjdqJHxY1yKlQv2XhlTml47JdFfDI68erY 0U95Moijbq5/bXjFfxGFCuM= X-Google-Smtp-Source: ABdhPJxAL2lCvi+TgAlBomm2DmztS/lH0e4+iC4JdWPcIGp1Lxg2GbRYcfceOlEp8fhFBkiUAZpCwA== X-Received: by 2002:a37:ef17:: with SMTP id j23mr11467878qkk.209.1617938100797; Thu, 08 Apr 2021 20:15:00 -0700 (PDT) Received: from LuizSampaio-PC.localdomain ([2804:14d:5c21:af45:3b27:576c:7dde:37f1]) by smtp.gmail.com with ESMTPSA id x1sm1003167qtr.97.2021.04.08.20.14.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Apr 2021 20:15:00 -0700 (PDT) From: Luiz Sampaio To: zbr@ioremap.net Cc: corbet@lwn.net, rikard.falkeborn@gmail.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Luiz Sampaio Subject: [PATCH v6 6/6] w1: ds2438: support for writing to offset register Date: Fri, 9 Apr 2021 00:15:33 -0300 Message-Id: <20210409031533.442123-7-sampaio.ime@gmail.com> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210409031533.442123-1-sampaio.ime@gmail.com> References: <20210409030942.441830-1-sampaio.ime@gmail.com> <20210409031533.442123-1-sampaio.ime@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Added a sysfs entry to support writing to the offset register on page1. This register is used to calibrate the chip canceling offset errors in the current ADC. This means that, over time, reading the IAD register will not return the correct current measurement, it will have an offset. Writing to the offset register if the two's complement of the current register while passing zero current to the load will calibrate the measurements. This change was tested on real hardware and it was able to calibrate the chip correctly. Signed-off-by: Luiz Sampaio --- .../ABI/stable/sysfs-driver-w1_ds2438 | 7 +++ Documentation/w1/slaves/w1_ds2438.rst | 11 ++++- drivers/w1/slaves/w1_ds2438.c | 49 +++++++++++++++++++ 3 files changed, 66 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/stable/sysfs-driver-w1_ds2438 b/Documentation/ABI/stable/sysfs-driver-w1_ds2438 index fa47437c11d9..d2e7681cc287 100644 --- a/Documentation/ABI/stable/sysfs-driver-w1_ds2438 +++ b/Documentation/ABI/stable/sysfs-driver-w1_ds2438 @@ -4,3 +4,10 @@ Contact: Luiz Sampaio Description: read the contents of the page1 of the DS2438 see Documentation/w1/slaves/w1_ds2438.rst for detailed information Users: any user space application which wants to communicate with DS2438 + +What: /sys/bus/w1/devices/.../offset +Date: April 2021 +Contact: Luiz Sampaio +Description: write the contents to the offset register of the DS2438 + see Documentation/w1/slaves/w1_ds2438.rst for detailed information +Users: any user space application which wants to communicate with DS2438 diff --git a/Documentation/w1/slaves/w1_ds2438.rst b/Documentation/w1/slaves/w1_ds2438.rst index ac8d0d4b0d0e..5c5573991351 100644 --- a/Documentation/w1/slaves/w1_ds2438.rst +++ b/Documentation/w1/slaves/w1_ds2438.rst @@ -22,7 +22,7 @@ is also often used in weather stations and applications such as: rain gauge, wind speed/direction measuring, humidity sensing, etc. Current support is provided through the following sysfs files (all files -except "iad" are readonly): +except "iad" and "offset" are readonly): "iad" ----- @@ -52,6 +52,15 @@ Internally when this file is read, the additional CRC byte is also obtained from the slave device. If it is correct, the 8 bytes page data are passed to userspace, otherwise an I/O error is returned. +"offset" +------- +This file controls the 2-byte Offset Register of the chip. +Writing a 2-byte value will change the Offset Register, which changes the +current measurement done by the chip. Changing this register to the two's complement +of the current register while forcing zero current through the load will calibrate +the chip, canceling offset errors in the current ADC. + + "temperature" ------------- Opening and reading this file initiates the CONVERT_T (temperature conversion) diff --git a/drivers/w1/slaves/w1_ds2438.c b/drivers/w1/slaves/w1_ds2438.c index 2cfdfedb584f..223a9aae6e2d 100644 --- a/drivers/w1/slaves/w1_ds2438.c +++ b/drivers/w1/slaves/w1_ds2438.c @@ -193,6 +193,34 @@ static int w1_ds2438_change_config_bit(struct w1_slave *sl, u8 mask, u8 value) return -1; } +static int w1_ds2438_change_offset_register(struct w1_slave *sl, u8 *value) +{ + unsigned int retries = W1_DS2438_RETRIES; + u8 w1_buf[9]; + u8 w1_page1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/]; + + if (w1_ds2438_get_page(sl, 1, w1_page1_buf) == 0) { + memcpy(&w1_buf[2], w1_page1_buf, DS2438_PAGE_SIZE - 1); /* last register reserved */ + w1_buf[7] = value[0]; /* change only offset register */ + w1_buf[8] = value[1]; + while (retries--) { + if (w1_reset_select_slave(sl)) + continue; + w1_buf[0] = W1_DS2438_WRITE_SCRATCH; + w1_buf[1] = 0x01; /* write to page 1 */ + w1_write_block(sl->master, w1_buf, 9); + + if (w1_reset_select_slave(sl)) + continue; + w1_buf[0] = W1_DS2438_COPY_SCRATCH; + w1_buf[1] = 0x01; + w1_write_block(sl->master, w1_buf, 2); + return 0; + } + } + return -1; +} + static int w1_ds2438_get_voltage(struct w1_slave *sl, int adc_input, uint16_t *voltage) { @@ -364,6 +392,25 @@ static ssize_t page1_read(struct file *filp, struct kobject *kobj, return ret; } +static ssize_t offset_write(struct file *filp, struct kobject *kobj, + struct bin_attribute *bin_attr, char *buf, + loff_t off, size_t count) +{ + struct w1_slave *sl = kobj_to_w1_slave(kobj); + int ret; + + mutex_lock(&sl->master->bus_mutex); + + if (w1_ds2438_change_offset_register(sl, buf) == 0) + ret = count; + else + ret = -EIO; + + mutex_unlock(&sl->master->bus_mutex); + + return ret; +} + static ssize_t temperature_read(struct file *filp, struct kobject *kobj, struct bin_attribute *bin_attr, char *buf, loff_t off, size_t count) @@ -430,6 +477,7 @@ static ssize_t vdd_read(struct file *filp, struct kobject *kobj, static BIN_ATTR_RW(iad, 0664, iad_write, 0); static BIN_ATTR_RO(page0, DS2438_PAGE_SIZE); static BIN_ATTR_RO(page1, DS2438_PAGE_SIZE); +static BIN_ATTR_WO(offset, 2); static BIN_ATTR_RO(temperature, 0/* real length varies */); static BIN_ATTR_RO(vad, 0/* real length varies */); static BIN_ATTR_RO(vdd, 0/* real length varies */); @@ -438,6 +486,7 @@ static struct bin_attribute *w1_ds2438_bin_attrs[] = { &bin_attr_iad, &bin_attr_page0, &bin_attr_page1, + &bin_attr_offset, &bin_attr_temperature, &bin_attr_vad, &bin_attr_vdd, -- 2.30.1