1 # Multi-host front panel phosphor buttons interface 2 3 Author: 4 Velumani T(velu), [velumanit@hcl](mailto:velumanit@hcl.com) 5 Naveen Moses S(naveen.moses), [naveen.mosess@hcl.com](mailto:naveen.mosess@hcl.com) 6 Primary assignee: 7 8 Other contributors: 9 10 Created: 11 August 3, 2021 12 13 ## Problem Description 14 Phosphor buttons module has currently option to monitor gpio events of power 15 and reset buttons and trigger power event handlers. 16 17 phosphor-buttons currently only support push type buttons.support for 18 different form factor inputs such as switches/MUX other than push type 19 buttons are needed for some hardwares. It will be helpful if we could 20 add option to support additional input types in phosphor button interfaces 21 and event handling. 22 23 Currently handler events are only based on monitoring gpio events 24 as input (power and reset).There may be cases where whe need to create 25 button interface which monitors non gpio events 26 and triggers button actions for example events based on dbus property changes. 27 28 ## Requirements 29 This feature is needed to support additonal phosphor button interfaces 30 corresponding to platform specific hardware buttons/MUX/Switches which are 31 available in the front panel apart from existing power and reset button 32 interfaces. 33 34 ## Background and References 35 The front panel of bmc has buttons like power button, reset button 36 in general the code for monitoring these buttons and triggering actions are 37 supported. 38 39 ``` 40 +----------------------------------------------+ 41 | | 42 | Front panel | 43 | | 44 | +--------------+ +--------------+ | 45 | | | | | | 46 | | power button | | reset button | | 47 | | | | | | 48 | +--------------+ +--------------+ | 49 | | 50 | | 51 | | 52 | | 53 +----------------------------------------------+ 54 ``` 55 56 platform specific front panel may contain additional hardware buttons or 57 mux switch 58 59 example for a multihost platform yosemite-V2 it has host selector switch mux 60 as additional button in front panel. 61 62 ``` 63 +---------------------------+ +------------+ 64 | | | | 65 | yv2 front panel | power/ ---------+| host 1 | 66 | | reset/serial mux | | | 67 | +----------------+ | control | +------------+ 68 | | | | | 69 | | power button |-+ | | +------------+ 70 | | | | | | | | 71 | +----------------+ | | |--------+| host 2 | 72 | | | | | | 73 | | | | +------------+ 74 | | | +---------------+ | 75 | +----------------+ | | | host | | +-------------+ 76 | | | | | | selector |------+ | | 77 | | reset button --|--------+ switch | |---------+ host 3 | 78 | | | | +---------------+ | | | 79 | +----------------+ | | +-------------+ 80 | | | 81 | | | +------------+ 82 | | | | | 83 | +----------------+ | |----------+ host 4 | 84 | | serial console +---------------------------------| | | 85 | | mux switch | | | +------------+ 86 | | | | | 87 | +----------------+ | | +-----------+ 88 | | +-----------| BMC | 89 | | | | 90 +---------------------------+ +-----------+ 91 92 ``` 93 94 There are two additional hardware buttons/switch available in the 95 frontpanel for yv2. 96 97 ## 1.Host selector switch (selector switch) 98 This host selector switch/selector switch has 4 gpio connected as input and 99 based on the gpio state values the host selector switch value is derived. 100 The possible switch values can vary from 0 to 10. 101 The specific mapping between gpio values and host selector values 102 can be stored as part of gpio json config. 103 104 yosemiteV2 platform has 1 bmc and 4 hosts and only one power button and 105 reset button. 106 107 For example, when the power button is pressed, 108 The value of the host selector switch position(1 to 10) decides whether the 109 power button action is needs to be triggered for bmc or any one of the 110 hosts. 111 112 This option is to use same power button and reset button for multiple hosts. 113 114 The power/reset button press events are triggered based on the value of 115 host selector switch position. 116 117 ### Example : 118 host selector position value = 0,bmc is mapped to power and reset buttons 119 host selector position value = 1,host 1 is mapped to power and reset buttons 120 host selector position value = 2,host 2 is mapped to power and reset buttons 121 host selector position value = 3,host 3 is mapped to power and reset buttons 122 host selector position value = 4,host 4 is mapped to power and reset buttons 123 124 ## 2.Serial console MUX switch 125 126 There is also uart console for each host and bmc which is connected via a 127 MUX switch. 128 129 At a time any one of the device (either bmc or any one host) can be accessed 130 via the console which is based on the UART MUX switch configuration. 131 132 Based on the position of the host selector switch, a separate handler interface 133 can configure the respective serial console device is selected. 134 135 ## 3.OCP debug card host selector button 136 137 An OCP debug card can be connected to yosemitev2 via usb for debugging purpose. 138 139 This is a extension which has three buttons : 140 1.Power button 141 2.reset button 142 3.host selector button 143 144 Power and reset buttons are mapped to the same gpio of frontpanel so no 145 separate event handling is required. 146 147 The host selector button purpose is same as that of the front panel 148 host selector switch in yosemitev2 front panel. The debug card host selector 149 button (push button) has different gpio lines than that of front panel 150 host selector switch gpios. 151 Whenever the debug host selector button is pressed the host 152 selector switch position value should be increased up to MaxPosition. 153 If the host selector switch value is more than MaxPosition then it 154 should be reset to zero. 155 156 # Proposed Design 157 Three high level changes are required in the phosphor button interface class 158 159 1. Add support for adding button interfaces which are monitoring more than 160 one gpio event and process with single event handler. 161 162 2. Add support to monitor button / switch interface event based on dbus 163 property changes (needed for serial console MUX). 164 165 3. Each button interface class can be extended with the following overridable 166 methods to allow platform specific logic if needed in a derived class. 167 168 - init() - This method may have gpio configuration and 169 event handler initialization. 170 171 - handleEvent() - This method may have custom event handling 172 routines for the respective button interface.This should be 173 be called from the main even handler function. 174 175 ## The host selector switch interface 176 177 The host selector switch has 4 gpios associated with it. host selector 178 switch button interface monitors these 4 gpio io events as sd-event 179 based event loop and a single event handler function is called for 180 all 4 gpio events. 181 182 Based on the 4 gpio state values, the host selector switch position value 183 is derived and stored as a dbus property with name "Position". 184 185 ### Host selector dbus interface details 186 1. Position(property) - This is the property which holds the current 187 value of the host selector switch based on the GPIO state. 188 189 2. MaxPosition(property) - This is the property which keeps the maximum 190 number of Position the Position property can hold.(This value is based 191 on the number of hosts available in the platform) 192 193 ## OCP Debug card host selector button interface 194 A separate interface for debug card host selector button is created. 195 196 This button interface monitors the corresponding gpio lines for debug card 197 host selecton button press and release event via sd-event based loop. 198 199 ### OCP Debug card host selector buton dbus interface details : 200 1. Released(signal) - This is signal is triggered in the ocp debug card event 201 handler when the ocp debug card button is pressed and released. 202 203 When the event handler is called once the button is released, 204 then the host selector switch dbus property "Position" is increased by 1. 205 The host selector switch dbus property value is rollover to zero after Position 206 value exceeds MaxPosition Value. 207 208 This way when power and reset button press events are handled, 209 the Host selector Position property is refered and based on the 210 Position respective power events are called. 211 212 ## serial console MUX interface 213 This button interface monitors for change in host selector switch Position dbus 214 property and based on the dbus property value change, corresponding serial 215 console is selected.mux value can be set as configuring 4 gpio lines dedicated 216 for the serial console mux. 217 ### Example 218 0 - bmc serial console 219 1 - host 1 serial console 220 2 - host 2 serial console 221 3 - host 3 serial console 222 4 - host 4 serial console 223 224 ### Change in power button and reset button interface event handler 225 If selector button instance is available,then the power button and reset 226 button pressed events must route to appropriate multihost dbus service name 227 228 ## Impacts 229 The change impacts are under phosphor buttons repo,the existing power and 230 reset button handlers are calling dbus calls for single host power events. 231 This calls should be modified to adapt corresponding multi host power events 232 and the respective host dbus object is based on host selector position. 233 234 ## Testing 235 The proposed design can be tested in a platform in which the multiple hosts 236 are connected.