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Tue, 12 Aug 2025 10:09:54 -0700 (PDT) Received: from [127.0.1.1] ([185.177.137.147]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-615a911451csm20060302a12.60.2025.08.12.10.09.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Aug 2025 10:09:52 -0700 (PDT) From: Yusuf Alper Bilgin Date: Tue, 12 Aug 2025 19:04:12 +0200 Subject: [PATCH 3/3] iio: adc: ltc2497: add temperature sensor support Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250812-ltc2495-v1-3-7bf4c6feec2e@gmail.com> References: <20250812-ltc2495-v1-0-7bf4c6feec2e@gmail.com> In-Reply-To: <20250812-ltc2495-v1-0-7bf4c6feec2e@gmail.com> To: Lars-Peter Clausen , Michael Hennerich , Jonathan Cameron , David Lechner , =?utf-8?q?Nuno_S=C3=A1?= , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Liam Beguin Cc: Michael Hennerich , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Yusuf Alper Bilgin X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1755018589; l=7778; i=y.alperbilgin@gmail.com; s=20250811; h=from:subject:message-id; bh=iyO00up7pExqdt6wTiA/2z0XMeAgUS+X5mkIQF9F00g=; b=CEJMp9UmnXizijTG5R6lE4pMOZZDU4w86PgVlCb97SQyPX+nqq5AczOzcXw5uSMRRR6P7IP/u fX7SCHPpgBsARYLgJgdCXiDGCCiRHhjlu/8s4cZ8gSbtzpaAhEID2J/ X-Developer-Key: i=y.alperbilgin@gmail.com; a=ed25519; pk=FtW2oyQ0+xlYU0XmhYiJYC3lNPtPrgeE6i4WXPwaFnY= The LTC2495 and LTC2499 include an internal temperature sensor. This patch adds support for reading it via a standard IIO temperature channel. Signed-off-by: Yusuf Alper Bilgin --- drivers/iio/adc/ltc2496.c | 1 + drivers/iio/adc/ltc2497-core.c | 80 ++++++++++++++++++++++++++++++++++++++---- drivers/iio/adc/ltc2497.c | 33 ++++++++++++++--- drivers/iio/adc/ltc2497.h | 7 +++- 4 files changed, 109 insertions(+), 12 deletions(-) diff --git a/drivers/iio/adc/ltc2496.c b/drivers/iio/adc/ltc2496.c index f06dd0b9a85819935abea6496abe2a808ac549c6..909dbd5f9aee877aafe423b47581ff4f36a76c52 100644 --- a/drivers/iio/adc/ltc2496.c +++ b/drivers/iio/adc/ltc2496.c @@ -90,6 +90,7 @@ static void ltc2496_remove(struct spi_device *spi) static const struct ltc2497_chip_info ltc2496_info = { .resolution = 16, .name = NULL, + .has_temp_channel = false, }; static const struct of_device_id ltc2496_of_match[] = { diff --git a/drivers/iio/adc/ltc2497-core.c b/drivers/iio/adc/ltc2497-core.c index 400f4fe5af30e8e16b75506726235f10f2a4237f..938259df4d27e9e26dea2be4112bef355adaaafb 100644 --- a/drivers/iio/adc/ltc2497-core.c +++ b/drivers/iio/adc/ltc2497-core.c @@ -72,8 +72,8 @@ static int ltc2497core_read(struct ltc2497core_driverdata *ddata, u8 address, in } static int ltc2497core_read_raw(struct iio_dev *indio_dev, - struct iio_chan_spec const *chan, - int *val, int *val2, long mask) + struct iio_chan_spec const *chan, + int *val, int *val2, long mask) { struct ltc2497core_driverdata *ddata = iio_priv(indio_dev); int ret; @@ -93,10 +93,52 @@ static int ltc2497core_read_raw(struct iio_dev *indio_dev, if (ret < 0) return ret; - *val = ret / 1000; - *val2 = ddata->chip_info->resolution + 1; + switch (chan->type) { + case IIO_VOLTAGE: + *val = ret / 1000; + *val2 = ddata->chip_info->resolution + 1; + + return IIO_VAL_FRACTIONAL_LOG2; + + case IIO_TEMP: + if (!ddata->chip_info->has_temp_channel) + return -EINVAL; + + /* + * The datasheet formula to get Temperature in Celsius is: + * Temp_C = (Conversion * Vref / temp_scale) - 273 + * + * To match the IIO framework's model of (raw + offset) * scale, + * and to get the final result in millidegrees Celsius: + * + * = ((Conversion * Vref / temp_scale) - 273) * 1000 + * = (Conversion - (273 * temp_scale / Vref)) * 1000 * Vref / temp_scale + * + * This gives us if the Vref is in mV: + * scale = Vref * 1000 / temp_scale + * offset = -273 * temp_scale / Vref + */ + *val = ret; + *val2 = ddata->chip_info->temp_scale; + + return IIO_VAL_FRACTIONAL; + + default: + return -EINVAL; + } + case IIO_CHAN_INFO_OFFSET: + if (chan->type != IIO_TEMP) + return -EINVAL; + + /* see the calculation above. Offset with (-273 * temp_scale / Vref) */ + ret = regulator_get_voltage(ddata->ref); + if (ret < 0) + return ret; - return IIO_VAL_FRACTIONAL_LOG2; + *val = -273 * ddata->chip_info->temp_scale; + *val2 = ret / 1000; + + return IIO_VAL_FRACTIONAL; default: return -EINVAL; @@ -124,6 +166,14 @@ static int ltc2497core_read_raw(struct iio_dev *indio_dev, .differential = 1, \ } +#define LTC2497_T_CHAN() { \ + .type = IIO_TEMP, \ + .channel = 0, \ + .address = (LTC2497_TEMP_CMD_ADDR), \ + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET), \ +} + static const struct iio_chan_spec ltc2497core_channel[] = { LTC2497_CHAN(0, LTC2497_SGL, "CH0"), LTC2497_CHAN(1, LTC2497_SGL, "CH1"), @@ -159,6 +209,8 @@ static const struct iio_chan_spec ltc2497core_channel[] = { LTC2497_CHAN_DIFF(7, LTC2497_DIFF | LTC2497_SIGN), }; +static const struct iio_chan_spec ltc2497_temp_channel = LTC2497_T_CHAN(); + static const struct iio_info ltc2497core_info = { .read_raw = ltc2497core_read_raw, }; @@ -180,8 +232,22 @@ int ltc2497core_probe(struct device *dev, struct iio_dev *indio_dev) indio_dev->info = <c2497core_info; indio_dev->modes = INDIO_DIRECT_MODE; - indio_dev->channels = ltc2497core_channel; - indio_dev->num_channels = ARRAY_SIZE(ltc2497core_channel); + + /* Dynamically create the channel list */ + if (ddata->chip_info->has_temp_channel) { + /* Allocate space for common channels + 1 temp channel */ + indio_dev->num_channels = ARRAY_SIZE(ltc2497core_channel) + 1; + indio_dev->channels = devm_kmemdup(dev, ltc2497core_channel, + sizeof(ltc2497core_channel), GFP_KERNEL); + if (!indio_dev->channels) + return -ENOMEM; + + memcpy((void *)&indio_dev->channels[ARRAY_SIZE(ltc2497core_channel)], + <c2497_temp_channel, sizeof(ltc2497_temp_channel)); + } else { + indio_dev->channels = ltc2497core_channel; + indio_dev->num_channels = ARRAY_SIZE(ltc2497core_channel); + } ret = ddata->result_and_measure(ddata, LTC2497_CONFIG_DEFAULT, NULL); if (ret < 0) diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c index 8f4665547b5b0d32084599f8557c40102c37a4ce..3f8515ef465d3fda7572d63ef3a265dec89079ea 100644 --- a/drivers/iio/adc/ltc2497.c +++ b/drivers/iio/adc/ltc2497.c @@ -86,11 +86,31 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata, return 0; } - ret = i2c_smbus_write_byte(st->client, - LTC2497_ENABLE | address); + /* + * Chips with temperature sensor support (e.g., LTC2495/LTC2499) + * require a two-byte command format to select any channel. + * + * To read the internal temperature, LTC2497_TEMP_CMD_ADDR is sent as + * the second byte. To read a voltage channel, LTC2497_EN2 is sent, + * which sets the default configuration: simultaneous 50/60Hz + * rejection, 1x speed, and gain=1. + * + * Chips without this feature use a standard single-byte command. + */ + if (ddata->chip_info->has_temp_channel) { + if (address == LTC2497_TEMP_CMD_ADDR) + ret = i2c_smbus_write_byte_data(st->client, LTC2497_ENABLE, + LTC2497_TEMP_CMD_ADDR); + else + ret = i2c_smbus_write_byte_data(st->client, LTC2497_ENABLE | address, + LTC2497_EN2); + + } else { + ret = i2c_smbus_write_byte(st->client, LTC2497_ENABLE | address); + } + if (ret) - dev_err(&st->client->dev, "i2c transfer failed: %pe\n", - ERR_PTR(ret)); + dev_err(&st->client->dev, "i2c transfer failed: %pe\n", ERR_PTR(ret)); return ret; } @@ -135,14 +155,19 @@ static const struct ltc2497_chip_info ltc2497_info[] = { [TYPE_LTC2495] = { .resolution = 16, .name = "ltc2495", + .has_temp_channel = true, + .temp_scale = 12250, /* 12.250 V per degree C -> 12250 mV */ }, [TYPE_LTC2497] = { .resolution = 16, .name = NULL, + .has_temp_channel = false, }, [TYPE_LTC2499] = { .resolution = 24, .name = "ltc2499", + .has_temp_channel = true, + .temp_scale = 1570000, /* 1570 V per degree C -> 1570000 mV */ }, }; diff --git a/drivers/iio/adc/ltc2497.h b/drivers/iio/adc/ltc2497.h index f2139f260c3fe4e8772c6db9c46331de775dcd5c..c133a4fb8092b1c6a66a7336016dd361783f531c 100644 --- a/drivers/iio/adc/ltc2497.h +++ b/drivers/iio/adc/ltc2497.h @@ -1,10 +1,15 @@ /* SPDX-License-Identifier: GPL-2.0-only */ -#define LTC2497_ENABLE 0xA0 +#define LTC2497_ENABLE 0xA0 +#define LTC2497_EN2 0x80 +#define LTC2497_IM 0x40 +#define LTC2497_TEMP_CMD_ADDR (LTC2497_EN2 | LTC2497_IM) struct ltc2497_chip_info { u32 resolution; const char *name; + bool has_temp_channel; + u32 temp_scale; /* in mV, for temp conversion */ }; struct ltc2497core_driverdata { -- 2.43.0