1*27ae70b8SShawn McCarney# Monitoring Chassis Power Good 2*27ae70b8SShawn McCarney 3*27ae70b8SShawn McCarney## Overview 4*27ae70b8SShawn McCarney 5*27ae70b8SShawn McCarneyThe power sequencer device provides a chassis power good (pgood) signal. This 6*27ae70b8SShawn McCarneyindicates that all of the main (non-standby) voltage rails are powered on. 7*27ae70b8SShawn McCarney 8*27ae70b8SShawn McCarneyThe `phosphor-power-sequencer` application periodically reads (polls) the 9*27ae70b8SShawn McCarneychassis pgood signal from a named GPIO. For more information, see 10*27ae70b8SShawn McCarney[Named GPIOs](named_gpios.md). 11*27ae70b8SShawn McCarney 12*27ae70b8SShawn McCarneyThe resulting chassis pgood value is used to set the `pgood` property for the 13*27ae70b8SShawn McCarneychassis. See [Chassis Status](chassis_status.md) for more information on this 14*27ae70b8SShawn McCarneyproperty. 15*27ae70b8SShawn McCarney 16*27ae70b8SShawn McCarneyIf the chassis pgood state is false when it should be true, a chassis power good 17*27ae70b8SShawn McCarney(pgood) fault has occurred. See [Power Good Faults](pgood_faults.md) for more 18*27ae70b8SShawn McCarneyinformation. 19*27ae70b8SShawn McCarney 20*27ae70b8SShawn McCarney## Unable to read chassis power good signal 21*27ae70b8SShawn McCarney 22*27ae70b8SShawn McCarney`phosphor-power-sequencer` may become unable to read the chassis power good 23*27ae70b8SShawn McCarneysignal from the named GPIO due to: 24*27ae70b8SShawn McCarney 25*27ae70b8SShawn McCarney- Hardware communication problems 26*27ae70b8SShawn McCarney - Unable to read from named GPIO after multiple retries. 27*27ae70b8SShawn McCarney- The `Available` property of the chassis changes to false. 28*27ae70b8SShawn McCarney 29*27ae70b8SShawn McCarney### During power on 30*27ae70b8SShawn McCarney 31*27ae70b8SShawn McCarneyIf `phosphor-power-sequencer` is unable to read the chassis power good signal 32*27ae70b8SShawn McCarneyduring a power on attempt, the application will do the following: 33*27ae70b8SShawn McCarney 34*27ae70b8SShawn McCarney- If this is a single chassis system: 35*27ae70b8SShawn McCarney - Log an error specifying the power on attempt failed due to an inability to 36*27ae70b8SShawn McCarney read the chassis power good status. 37*27ae70b8SShawn McCarney - `phosphor-chassis-state-manager` will [power off](powering_off.md) the 38*27ae70b8SShawn McCarney system. 39*27ae70b8SShawn McCarney- If this is a multiple chassis system: 40*27ae70b8SShawn McCarney - If the chassis is experiencing a blackout: 41*27ae70b8SShawn McCarney - Log an error specifying an input power problem. 42*27ae70b8SShawn McCarney - If the chassis is not experiencing a blackout: 43*27ae70b8SShawn McCarney - Log an error specifying the power on attempt failed due to an inability to 44*27ae70b8SShawn McCarney read the chassis power good status. 45*27ae70b8SShawn McCarney - If the read failure was due to hardware communication problems, add the 46*27ae70b8SShawn McCarney inventory path of the chassis to the error log. This may result in 47*27ae70b8SShawn McCarney hardware isolation, which will cause the `Enabled` property of the chassis 48*27ae70b8SShawn McCarney to be false. 49*27ae70b8SShawn McCarney - `phosphor-chassis-state-manager` will power the system 50*27ae70b8SShawn McCarney [off](powering_off.md) and then [on](powering_on.md) again. If the chassis's 51*27ae70b8SShawn McCarney `Available` or `Enabled` property is false, the chassis will not be powered 52*27ae70b8SShawn McCarney on. 53*27ae70b8SShawn McCarney 54*27ae70b8SShawn McCarney### After power on 55*27ae70b8SShawn McCarney 56*27ae70b8SShawn McCarneyIf `phosphor-power-sequencer` is unable to read the chassis power good signal 57*27ae70b8SShawn McCarneyafter the chassis powered on, the application will do the following: 58*27ae70b8SShawn McCarney 59*27ae70b8SShawn McCarney- If this is a single chassis system: 60*27ae70b8SShawn McCarney - Log an error specifying an inability to read the chassis power good status. 61*27ae70b8SShawn McCarney - Do **not** power off the system. 62*27ae70b8SShawn McCarney - Leave the `pgood` property set to the value 1. 63*27ae70b8SShawn McCarney- If this is a multiple chassis system: 64*27ae70b8SShawn McCarney - If the chassis is experiencing a blackout: 65*27ae70b8SShawn McCarney - Set `pgood` value to 0. 66*27ae70b8SShawn McCarney - Log an error specifying an input power problem. 67*27ae70b8SShawn McCarney - Power the system off and then on again. If the chassis's `Available` 68*27ae70b8SShawn McCarney property is false, the chassis will not be powered on. 69*27ae70b8SShawn McCarney - If the chassis is not experiencing a blackout: 70*27ae70b8SShawn McCarney - Log an error specifying an inability to read the chassis power good 71*27ae70b8SShawn McCarney status. 72*27ae70b8SShawn McCarney - Do **not** power off the system. 73*27ae70b8SShawn McCarney - Leave the `pgood` property set to the value 1. 74