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 45C6AC433ED for ; Sat, 3 Apr 2021 04:48:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2130860240 for ; Sat, 3 Apr 2021 04:48:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236402AbhDCEsD (ORCPT ); Sat, 3 Apr 2021 00:48:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236361AbhDCEr6 (ORCPT ); Sat, 3 Apr 2021 00:47:58 -0400 Received: from mail-qk1-x733.google.com (mail-qk1-x733.google.com [IPv6:2607:f8b0:4864:20::733]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CB441C0613E6 for ; Fri, 2 Apr 2021 21:47:55 -0700 (PDT) Received: by mail-qk1-x733.google.com with SMTP id o5so7011762qkb.0 for ; Fri, 02 Apr 2021 21:47:55 -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=Ct0KqhECfaQPeqAmFu0by9DQtEz5Znm3fSMIKLGYhYE=; b=qNNGgftYPJm6jYC4aK1zEzAx3amCRrO1t4lGqigb3MaqK50sFC8eWTRJcmmTFhhwF9 K/svan4maNTMdfAVPcVXjofivLhOG9VG86DUshBexyrFWvtvMVbe2zVIMygDvp6XWHQP aqNTyWwGFQuMKrOubgccMaj1ikF/DmDCr/aeLj6kIQ79un3gCEa/rBTrlDfV9AxU+qju x/U+tEToDEBsja5ySy0d5ArcOAOrH4us0+H0jXbRvrMsVhB5MEsbvYFmqIyRI3ajA2nq t7JjESGzHRKMVqPOlmCeWcsDamQxKBiPywqdK+NQENCVVVpk5Q8Pinc9oiPXc7CF9vFQ Hgsg== 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=Ct0KqhECfaQPeqAmFu0by9DQtEz5Znm3fSMIKLGYhYE=; b=OUerLrcMCBGIJlJiQyb4Hb2MEJqWio8vZpKrWX6bb5QOs3RIIzhFKce6qr7SeS8gtj PhiJcKySfDxHuNyy9zyk9IifF+cnDCEba3WsdRNjphjaEAo4VKR5/s153THr0YJNxDnz LilkTnh/Re6jQlQMxy4DzO/iqflGLDIP4PJ2TIZjqoG4cZ66YUnHMs6Ft0ligyoaSLtw ooUyQYCRjS3AVi5H/x/4MTXRzPEFzQAZ7iDu7FCOT0M4bpFpHPiJMBdvXOv/soJwqsuD 1QjbJqtu7K0G2Yh5atEsvyTCK5wES1PxgkPyaJHzlCAwNofbEsONNe9chIWf/1naucEg o0vg== X-Gm-Message-State: AOAM5323BDPn4xogp4UhaxmZ4YFNZ2K3LHpS4xr48JG64ZBnkF7/2JvJ bGmEc9FzZtmA2yKnliEvP1c= X-Google-Smtp-Source: ABdhPJyJR5rJCXrFWQKo1y5X5m4jH2FgQRvBXgLU7+VwqJ1TIj0kKyu+wSojUBOB4j8i+w6oMF9ucQ== X-Received: by 2002:a05:620a:16b1:: with SMTP id s17mr15928466qkj.302.1617425275095; Fri, 02 Apr 2021 21:47:55 -0700 (PDT) Received: from LuizSampaio-PC.localdomain ([2804:14d:5cd3:8f4f:bad9:1dc4:19d9:7ce3]) by smtp.gmail.com with ESMTPSA id k126sm8800598qkb.4.2021.04.02.21.47.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Apr 2021 21:47:54 -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, Luiz Sampaio Subject: [PATCH v3 9/9] w1: ds2438: support for writing to offset register Date: Sat, 3 Apr 2021 01:48:21 -0300 Message-Id: <20210403044821.390485-9-sampaio.ime@gmail.com> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210403044821.390485-1-sampaio.ime@gmail.com> References: <20210403044547.390226-1-sampaio.ime@gmail.com> <20210403044821.390485-1-sampaio.ime@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 --- Documentation/w1/slaves/w1_ds2438.rst | 11 +++++- drivers/w1/slaves/w1_ds2438.c | 49 +++++++++++++++++++++++++++ 2 files changed, 59 insertions(+), 1 deletion(-) 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); /* register 7 is 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(iad, 0664, iad_read, 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