[PATCH 2/2] w1: w1_therm: Add support for GXCAS GX20MH01 device.

From: Ivan Zaentsev
Date: Fri Sep 04 2020 - 12:00:49 EST

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GX20MH01 device shares family number 0x28 with DS18B20. The device
is generally compatible with DS18B20. Added are the lowest 2^-5, 2^-6
temperature bits in Config register; R2 bit in Config register
enabling 13 and 14 bit resolutions. It is powered up in 14 bit mode.

Signed-off-by: Ivan Zaentsev <ivan.zaentsev@xxxxxxxxxxxxx>
---
.../ABI/testing/sysfs-driver-w1_therm | 4 +-
Documentation/w1/slaves/w1_therm.rst | 15 ++-
drivers/w1/slaves/w1_therm.c | 106 +++++++++++++-----
3 files changed, 92 insertions(+), 33 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-driver-w1_therm b/Documentation/ABI/testing/sysfs-driver-w1_therm
index b44b51a88c5e..9f05bcdcd762 100644
--- a/Documentation/ABI/testing/sysfs-driver-w1_therm
+++ b/Documentation/ABI/testing/sysfs-driver-w1_therm
@@ -49,7 +49,7 @@ Description:
will be changed only in device RAM, so it will be cleared when
power is lost. Trigger a 'save' to EEPROM command to keep
values after power-on. Read or write are :
- * '9..12': device resolution in bit
+ * '9..14': device resolution in bit
or resolution to set in bit
* '-xx': xx is kernel error when reading the resolution
* Anything else: do nothing
@@ -89,7 +89,7 @@ Description:
*write* :
* '0' : save the 2 or 3 bytes to the device EEPROM
(i.e. TH, TL and config register)
- * '9..12' : set the device resolution in RAM
+ * '9..14' : set the device resolution in RAM
(if supported)
* Anything else: do nothing
refer to Documentation/w1/slaves/w1_therm.rst for detailed
diff --git a/Documentation/w1/slaves/w1_therm.rst b/Documentation/w1/slaves/w1_therm.rst
index f1148181f53e..00376501a5ef 100644
--- a/Documentation/w1/slaves/w1_therm.rst
+++ b/Documentation/w1/slaves/w1_therm.rst
@@ -6,6 +6,7 @@ Supported chips:

* Maxim ds18*20 based temperature sensors.
* Maxim ds1825 based temperature sensors.
+ * GXCAS GC20MH01 temperature sensor.

Author: Evgeniy Polyakov <johnpol@xxxxxxxxxxx>

@@ -13,8 +14,8 @@ Author: Evgeniy Polyakov <johnpol@xxxxxxxxxxx>
Description
-----------

-w1_therm provides basic temperature conversion for ds18*20 devices, and the
-ds28ea00 device.
+w1_therm provides basic temperature conversion for ds18*20, ds28ea00, GX20MH01
+devices.

Supported family codes:

@@ -130,4 +131,12 @@ conversion and temperature reads 85.00 (powerup value) or 127.94 (insufficient
power), the driver returns a conversion error. Bit mask ``2`` enables poll for
conversion completion (normal power only) by generating read cycles on the bus
after conversion starts. In parasite power mode this feature is not available.
-Feature bit masks may be combined (OR).
+Feature bit masks may be combined (OR). See accompanying sysfs documentation:
+:ref:`Documentation/w1/slaves/w1_therm.rst <w1_therm>`
+
+GX20MH01 device shares family number 0x28 with DS18*20. The device is generally
+compatible with DS18B20. Added are lowest 2^-5, 2^-6 temperature bits in Config
+register; R2 bit in Config register enabling 13 and 14 bit resolutions. The
+device is powered up in 14-bit resolution mode. The conversion times specified
+in the datasheet are too low and have to be increased. The device supports
+driver features ``1`` and ``2``.
diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index 9b2d96335a70..f6b0e0320ffc 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -80,6 +80,18 @@ static u16 bulk_read_device_counter; /* =0 as per C standard */
#define W1_POLL_CONVERT_TEMP 2000 /* Timeout for W1_CONVERT_TEMP, ms */
#define W1_POLL_RECALL_EEPROM 500 /* Timeout for W1_RECALL_EEPROM, ms*/

+/* Masks for resolution functions, work with all devices */
+/* Bit mask for config register for all devices, bits 7,6,5 */
+#define W1_THERM_RESOLUTION_MASK 0xE0
+/* Bit offset of resolution in config register for all devices */
+#define W1_THERM_RESOLUTION_SHIFT 5
+/* Bit offset of resolution in config register for all devices */
+#define W1_THERM_RESOLUTION_SHIFT 5
+/* Add this to bit value to get resolution */
+#define W1_THERM_RESOLUTION_MIN 9
+/* Maximum allowed value */
+#define W1_THERM_RESOLUTION_MAX 14
+
/* Helpers Macros */

/*
@@ -523,7 +535,9 @@ static inline int w1_DS18B20_convert_time(struct w1_slave *sl)
if (SLAVE_CONV_TIME_OVERRIDE(sl) != CONV_TIME_DEFAULT)
return SLAVE_CONV_TIME_OVERRIDE(sl);

- /* Return the conversion time from datasheet, depending on resolution */
+ /* Return the conversion time, depending on resolution,
+ * select maximum conversion time among all compatible devices
+ */
switch (SLAVE_RESOLUTION(sl)) {
case 9:
ret = 95;
@@ -535,6 +549,14 @@ static inline int w1_DS18B20_convert_time(struct w1_slave *sl)
ret = 375;
break;
case 12:
+ ret = 750;
+ break;
+ case 13:
+ ret = 850; /* GX20MH01 only. Datasheet says 500ms, but that's not enough. */
+ break;
+ case 14:
+ ret = 1600; /* GX20MH01 only. Datasheet says 1000ms - not enough */
+ break;
default:
ret = 750;
}
@@ -568,62 +590,71 @@ static inline int w1_DS18S20_write_data(struct w1_slave *sl,
static inline int w1_DS18B20_set_resolution(struct w1_slave *sl, int val)
{
int ret;
- u8 new_config_register[3]; /* array of data to be written */
struct therm_info info, info2;

- /* resolution of DS18B20 is in the range [9..12] bits */
- if (val < 9 || val > 12)
+ /* DS18B20 resolution is 9 to 12 bits */
+ /* GX20MH01 resolution is 9 to 14 bits */
+ if (val < W1_THERM_RESOLUTION_MIN || val > W1_THERM_RESOLUTION_MAX)
return -EINVAL;

- val -= 9; /* soustract 9 the lowest resolution in bit */
- val = (val << 5); /* shift to position bit 5 & bit 6 */
+ /* Calc bit value from resolution */
+ val = (val - W1_THERM_RESOLUTION_MIN) << W1_THERM_RESOLUTION_SHIFT;

/*
* Read the scratchpad to change only the required bits
* (bit5 & bit 6 from byte 4)
*/
ret = read_scratchpad(sl, &info);
- if (!ret) {
- new_config_register[0] = info.rom[2];
- new_config_register[1] = info.rom[3];
- /* config register is byte 4 & mask 0b10011111*/
- new_config_register[2] = (info.rom[4] & 0x9F) |
- (u8) val;
- } else
+
+ if (ret)
return ret;

+
+ info.rom[4] &= ~W1_THERM_RESOLUTION_MASK;
+ info.rom[4] |= val;
+
/* Write data in the device RAM */
- ret = w1_DS18B20_write_data(sl, new_config_register);
+ ret = w1_DS18B20_write_data(sl, info.rom + 2);
if (ret)
return ret;

- /* Some DS18B20 clones don't support resolution change, read back to verify */
+ /* Have to read back the resolution to verify an actual value
+ * GX20MH01 and DS18B20 are indistinguishable by family number, but resolutions differ
+ * Some DS18B20 clones don't support resolution change
+ */
ret = read_scratchpad(sl, &info2);
if (ret)
+ /* Scratchpad read fail */
return ret;

- if ((info2.rom[4] & 0x9F) == (info.rom[4] & 0x9F))
+ if ((info2.rom[4] & W1_THERM_RESOLUTION_MASK) == (info.rom[4] & W1_THERM_RESOLUTION_MASK))
return 0;
- else
- return -EIO;
+
+ /* Resolution verify error */
+ return -EIO;
}

static inline int w1_DS18B20_get_resolution(struct w1_slave *sl)
{
int ret;
- u8 config_register;
+ int resolution;
struct therm_info info;

ret = read_scratchpad(sl, &info);

- if (!ret) {
- config_register = info.rom[4]; /* config register is byte 4 */
- config_register &= 0x60; /* 0b01100000 keep only bit 5 & 6 */
- config_register = (config_register >> 5); /* shift */
- config_register += 9; /* add 9 the lowest resolution in bit */
- ret = (int) config_register;
- }
- return ret;
+ if (ret)
+ return ret;
+
+ resolution = ((info.rom[4] & W1_THERM_RESOLUTION_MASK) >> W1_THERM_RESOLUTION_SHIFT)
+ + W1_THERM_RESOLUTION_MIN;
+ /* GX20MH01 has one special case:
+ * >=14 means 14 bits when getting resolution from bit value.
+ * Other devices have no more then 12 bits.
+ */
+ if (resolution > W1_THERM_RESOLUTION_MAX)
+ resolution = W1_THERM_RESOLUTION_MAX;
+
+ return resolution;
}

/**
@@ -636,11 +667,28 @@ static inline int w1_DS18B20_get_resolution(struct w1_slave *sl)
*/
static inline int w1_DS18B20_convert_temp(u8 rom[9])
{
- s16 t = le16_to_cpup((__le16 *)rom);
+ int t;
+ u32 bv;
+
+ /* Config register bit R2 = 1 - GX20MH01 in 13 or 14 bit resolution mode */
+ if (rom[4] & 0x80) {
+ /* Signed 16-bit value to unsigned, cpu order */
+ bv = le16_to_cpup((__le16 *)rom);
+
+ /* Insert two temperature bits from config register */
+ /* Avoid arithmetic shift of signed value */
+ bv = (bv << 2) | (rom[4] & 3);

+ t = (int) sign_extend32(bv, 17); /* Degrees, lowest bit is 2^-6 */
+ return (t*1000)/64; /* Millidegrees */
+ }
+
+ t = (int)le16_to_cpup((__le16 *)rom);
return t*1000/16;
}

+
+
/**
* w1_DS18S20_convert_temp() - temperature computation for DS18S20
* @rom: data read from device RAM (8 data bytes + 1 CRC byte)
@@ -672,6 +720,7 @@ static inline int w1_DS18S20_convert_temp(u8 rom[9])
}

/* Device capability description */
+/* GX20MH01 device shares family number and structure with DS18B20 */

static struct w1_therm_family_converter w1_therm_families[] = {
{
@@ -693,6 +742,7 @@ static struct w1_therm_family_converter w1_therm_families[] = {
.bulk_read = true
},
{
+ /* Also used for GX20MH01 */
.f = &w1_therm_family_DS18B20,
.convert = w1_DS18B20_convert_temp,
.get_conversion_time = w1_DS18B20_convert_time,
--
2.25.1

Next message: Steven Price: "[PATCH v2 1/2] arm64: kvm: Save/restore MTE registers"
Previous message: Steven Price: "[PATCH v2 2/2] arm64: kvm: Introduce MTE VCPU feature"
In reply to: Ivan Zaentsev: "[PATCH 1/2] w1: w1_therm: Add sysfs entries to control conversion time and driver features"
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