w1: w1_therm: Add support for GXCAS GX20MH01 device.

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@wirenboard.ru>
Link: https://lore.kernel.org/r/20200904160004.87710-2-ivan.zaentsev@wirenboard.ru
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/ABI/testing/sysfs-driver-w1_therm b/Documentation/ABI/testing/sysfs-driver-w1_therm
index b44b51a..9f05bcd 100644 (file)
--- 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 f114818..0037650 100644 (file)
--- 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@2ka.mipt.ru>
 
@@ -13,8 +14,8 @@ Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
 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 9b2d963..f6b0e03 100644 (file)
--- 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,