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dmarc=pass (p=none dis=none) header.from=utu.fi Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=utu.fi Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=utu.fi header.i=@utu.fi header.a=rsa-sha256 header.s=out-utu-v3 header.b=BYOdEAWJ Received: from smtp-03.utu.fi (smtp-03.utu.fi [130.232.207.30]) by fortymile.utu.fi with ESMTPS id 6A29vSRr023761-6A29vSRt023761 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Mon, 2 Nov 2026 11:57:28 +0200 Received: from ex19-16.utu.fi ([130.232.247.56]) by smtp-03.utu.fi with esmtps (TLS1.2) tls TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1xNonA-00HHFg-3x; Mon, 02 Nov 2026 11:57:28 +0200 Received: from lorpotin (91.145.105.139) by ex19-16.utu.fi (130.232.247.56) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.56; Mon, 2 Nov 2026 11:57:27 +0200 From: Jaakko Koivisto To: Andreas Klinger , Jonathan Cameron , David Lechner , =?UTF-8?q?Nuno=20S=C3=A1?= , Andy Shevchenko CC: , , Jaakko Koivisto Subject: [PATCH v2 5/5] iio: chemical: sgp40: Implement turn_heater_off-command Date: Mon, 2 Nov 2026 11:56:02 +0200 Message-ID: <20261102095602.333752-1-jmatko@utu.fi> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261102091258.247402-1-jmatko@utu.fi> References: <20261102091258.247402-1-jmatko@utu.fi> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: ex19-10.utu.fi (130.232.247.50) To ex19-16.utu.fi (130.232.247.56) X-FEAS-BEC-Info: WlpIGw0aAQkEARIJHAEHBlJSCRoLAAEeDUhZUEhYSFhIWkhZXkguLT4lWFxYWFhYWFBeUVxfSFhISFpdSAIJCQMDB0YFCUYDBwEeARscBygdHB1GDgFIWUhZXkgJAygB HEUDBAEGDw0aRgwNSFhIWkhZXEhZW1hGWltaRlpYX0ZbWEhQSFhIWEhdSFhIWEhYSFleSAkDKAEcRQMEAQYPDRpGDA1IWEhZXUgJBgwRKAMNGgYNBEYHGg9IWEhaWUgM BA0LAAYNGigKCREEAQoaDUYLBwVIWEhaXUgEAQYdEEUBAQcoHg8NGkYDDRoGDQRGBxoPSFhIWVBIBh0GB0YbCSgJBgkEBw9GCwcFSFg= X-FEAS-Client-IP: 130.232.207.30 X-FE-Last-Public-Client-IP: 130.232.207.30 X-FE-Policy-ID: 3:5:2:SYSTEM X-FE-Hostname: fortymile.utu.fi DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; d=utu.fi; s=out-utu-v3; c=relaxed/relaxed; h=from:to:cc:subject:date:message-id:references:mime-version:content-type; bh=O3jVSvvryYZl7OF3FZBbst06ttsT1TkPtiH56l6h7gM=; b=BYOdEAWJzH2vOSXkviwG/cx4EGPYm5HH3Q4+EdjW7Y+9+TZ+w8Kb4NYVH+uO0zmNku9G9we0+Plp qpIPbmHrwOCHHAkvia2f0joAgSbIO9HvDTkzQY3lPEBPJvPCDmy8iy50saCg7gWxdNm37UTL886+ d1eWtaqW/uHy44rmzt6g83Q+in0Wl8lg0C5BZtOEo/GQMy18NPLDfJ1M7/ICha3KkdButRBOF5tg beKoK3BPDXEpv2lPUrXeaqQpEkeWKTNFcOGD4QlZ+iR/FDOxpibYd71GJCrCbnTpHXIVDuCOazGK GOrXsm+Zcrg4B0o7HHDblviIbOQWPriUeTUNXg== Add functionality for turning the SGP40 sensor heating element on or off manually. After turning the heater off, the sensor enters idle mode. Track the state of the heater in the driver, as the device does not expose current heater state via any register. Turning the heater off saves approx. 2.5 mA compared to regular operation. The heating element is automatically turned back on when measurement is performed. Signed-off-by: Jaakko Koivisto --- drivers/iio/chemical/sgp40.c | 62 +++++++++++++++++++++++++++++++++++- 1 file changed, 61 insertions(+), 1 deletion(-) diff --git a/drivers/iio/chemical/sgp40.c b/drivers/iio/chemical/sgp40.c index 278390bc6b04..87df8d79fe6e 100644 --- a/drivers/iio/chemical/sgp40.c +++ b/drivers/iio/chemical/sgp40.c @@ -54,7 +54,8 @@ struct sgp40_data { int rht; int temp; int res_calibbias; - /* Prevent concurrent access to rht, tmp, calibbias */ + bool heater_enabled; + /* Prevent concurrent access to rht, tmp, calibbias, heater_enabled */ struct mutex lock; }; @@ -263,6 +264,27 @@ static int sgp40_execute_self_test(struct sgp40_data *data) } } +static int sgp40_turn_heater_off(struct sgp40_data *data) +{ + int ret; + struct i2c_client *client = data->client; + struct sgp40_tg_measure turn_off = { .command = {0x36, 0x15} }; + + guard(mutex)(&data->lock); + + ret = i2c_master_send(client, (char *)&turn_off, sizeof(turn_off.command)); + if (ret < 0) + return ret; + if (ret != sizeof(turn_off.command)) + return dev_err_probe(data->dev, -EIO, + "i2c_master_send ret: %d, expected %zu", ret, sizeof(turn_off.command)); + + fsleep(1000); /* Max duration for command turn_heater_off. Datasheet table 8. */ + data->heater_enabled = false; + + return 0; +} + static int sgp40_measure_resistance_raw(struct sgp40_data *data, u16 *resistance_raw) { int ret; @@ -293,6 +315,7 @@ static int sgp40_measure_resistance_raw(struct sgp40_data *data, u16 *resistance return -EIO; } msleep(30); + data->heater_enabled = true; ret = i2c_master_recv(client, (u8 *)&tgres, sizeof(tgres)); if (ret < 0) @@ -423,10 +446,47 @@ static ssize_t serialnumber_show(struct device *dev, return sysfs_emit_at(buf, 0, "%llu\n", serial_number); } +static ssize_t heater_enable_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t len) +{ + int ret; + u16 __ignore; + bool val; + struct sgp40_data *data = iio_priv(dev_to_iio_dev(dev)); + + ret = kstrtobool(buf, &val); + if (ret) + return ret; + + if (val) + ret = sgp40_measure_resistance_raw(data, &__ignore); + else + ret = sgp40_turn_heater_off(data); + + if (ret) + return ret; + + return len; +} + +static ssize_t heater_enable_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct sgp40_data *data = iio_priv(dev_to_iio_dev(dev)); + + guard(mutex)(&data->lock); + + return sysfs_emit(buf, "%d\n", data->heater_enabled); +} + static IIO_DEVICE_ATTR_RO(serialnumber, 0); +static IIO_DEVICE_ATTR_RW(heater_enable, 0); static struct attribute *sgp40_attributes[] = { &iio_dev_attr_serialnumber.dev_attr.attr, + &iio_dev_attr_heater_enable.dev_attr.attr, NULL }; -- 2.56.0