1*4882a593SmuzhiyunKernel driver ltc4261 2*4882a593Smuzhiyun===================== 3*4882a593Smuzhiyun 4*4882a593SmuzhiyunSupported chips: 5*4882a593Smuzhiyun 6*4882a593Smuzhiyun * Linear Technology LTC4261 7*4882a593Smuzhiyun 8*4882a593Smuzhiyun Prefix: 'ltc4261' 9*4882a593Smuzhiyun 10*4882a593Smuzhiyun Addresses scanned: - 11*4882a593Smuzhiyun 12*4882a593Smuzhiyun Datasheet: 13*4882a593Smuzhiyun 14*4882a593Smuzhiyun http://cds.linear.com/docs/Datasheet/42612fb.pdf 15*4882a593Smuzhiyun 16*4882a593SmuzhiyunAuthor: Guenter Roeck <linux@roeck-us.net> 17*4882a593Smuzhiyun 18*4882a593Smuzhiyun 19*4882a593SmuzhiyunDescription 20*4882a593Smuzhiyun----------- 21*4882a593Smuzhiyun 22*4882a593SmuzhiyunThe LTC4261/LTC4261-2 negative voltage Hot Swap controllers allow a board 23*4882a593Smuzhiyunto be safely inserted and removed from a live backplane. 24*4882a593Smuzhiyun 25*4882a593Smuzhiyun 26*4882a593SmuzhiyunUsage Notes 27*4882a593Smuzhiyun----------- 28*4882a593Smuzhiyun 29*4882a593SmuzhiyunThis driver does not probe for LTC4261 devices, since there is no register 30*4882a593Smuzhiyunwhich can be safely used to identify the chip. You will have to instantiate 31*4882a593Smuzhiyunthe devices explicitly. 32*4882a593Smuzhiyun 33*4882a593SmuzhiyunExample: the following will load the driver for an LTC4261 at address 0x10 34*4882a593Smuzhiyunon I2C bus #1:: 35*4882a593Smuzhiyun 36*4882a593Smuzhiyun $ modprobe ltc4261 37*4882a593Smuzhiyun $ echo ltc4261 0x10 > /sys/bus/i2c/devices/i2c-1/new_device 38*4882a593Smuzhiyun 39*4882a593Smuzhiyun 40*4882a593SmuzhiyunSysfs entries 41*4882a593Smuzhiyun------------- 42*4882a593Smuzhiyun 43*4882a593SmuzhiyunVoltage readings provided by this driver are reported as obtained from the ADC 44*4882a593Smuzhiyunregisters. If a set of voltage divider resistors is installed, calculate the 45*4882a593Smuzhiyunreal voltage by multiplying the reported value with (R1+R2)/R2, where R1 is the 46*4882a593Smuzhiyunvalue of the divider resistor against the measured voltage and R2 is the value 47*4882a593Smuzhiyunof the divider resistor against Ground. 48*4882a593Smuzhiyun 49*4882a593SmuzhiyunCurrent reading provided by this driver is reported as obtained from the ADC 50*4882a593SmuzhiyunCurrent Sense register. The reported value assumes that a 1 mOhm sense resistor 51*4882a593Smuzhiyunis installed. If a different sense resistor is installed, calculate the real 52*4882a593Smuzhiyuncurrent by dividing the reported value by the sense resistor value in mOhm. 53*4882a593Smuzhiyun 54*4882a593SmuzhiyunThe chip has two voltage sensors, but only one set of voltage alarm status bits. 55*4882a593SmuzhiyunIn many many designs, those alarms are associated with the ADIN2 sensor, due to 56*4882a593Smuzhiyunthe proximity of the ADIN2 pin to the OV pin. ADIN2 is, however, not available 57*4882a593Smuzhiyunon all chip variants. To ensure that the alarm condition is reported to the user, 58*4882a593Smuzhiyunreport it with both voltage sensors. 59*4882a593Smuzhiyun 60*4882a593Smuzhiyun======================= ============================= 61*4882a593Smuzhiyunin1_input ADIN2 voltage (mV) 62*4882a593Smuzhiyunin1_min_alarm ADIN/ADIN2 Undervoltage alarm 63*4882a593Smuzhiyunin1_max_alarm ADIN/ADIN2 Overvoltage alarm 64*4882a593Smuzhiyun 65*4882a593Smuzhiyunin2_input ADIN voltage (mV) 66*4882a593Smuzhiyunin2_min_alarm ADIN/ADIN2 Undervoltage alarm 67*4882a593Smuzhiyunin2_max_alarm ADIN/ADIN2 Overvoltage alarm 68*4882a593Smuzhiyun 69*4882a593Smuzhiyuncurr1_input SENSE current (mA) 70*4882a593Smuzhiyuncurr1_alarm SENSE overcurrent alarm 71*4882a593Smuzhiyun======================= ============================= 72