238 lines
10 KiB
Markdown
238 lines
10 KiB
Markdown
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# Multi-host front panel phosphor buttons interface
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Author: Velumani T(velu), [velumanit@hcl](mailto:velumanit@hcl.com) Naveen Moses
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S(naveen.moses), [naveen.mosess@hcl.com](mailto:naveen.mosess@hcl.com)
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Other contributors:
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Created: August 3, 2021
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## Problem Description
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Phosphor buttons module has currently option to monitor gpio events of power and
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reset buttons and trigger power event handlers.
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phosphor-buttons currently only support push type buttons.support for different
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form factor inputs such as switches/MUX other than push type buttons are needed
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for some hardwares. It will be helpful if we could add option to support
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additional input types in phosphor button interfaces and event handling.
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Currently handler events are only based on monitoring gpio events as input
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(power and reset).There may be cases where we need to create button interface
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which monitors non gpio events and triggers button actions for example events
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based on dbus property changes.
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## Requirements
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This feature is needed to support additional phosphor button interfaces
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corresponding to platform specific hardware buttons/MUX/Switches which are
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available in the front panel apart from existing power and reset button
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interfaces.
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## Background and References
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The front panel of bmc has buttons like power button, reset button in general
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the code for monitoring these buttons and triggering actions are supported.
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```
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+----------------------------------------------+
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| Front panel |
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| +--------------+ +--------------+ |
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| | power button | | reset button | |
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| +--------------+ +--------------+ |
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+----------------------------------------------+
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```
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platform specific front panel may contain additional hardware buttons or mux
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switch
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example for a multihost platform yosemite-V2 it has host selector switch mux as
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additional button in front panel.
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```
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+---------------------------+ +------------+
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| yv2 front panel | power/ ---------+| host 1 |
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| | reset/serial mux | | |
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| +----------------+ | control | +------------+
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| | power button |-+ | | +------------+
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| +----------------+ | | |--------+| host 2 |
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| | | | +------------+
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| | | +---------------+ |
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| +----------------+ | | | host | | +-------------+
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| | | | | | selector |------+ | |
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| | reset button --|--------+ switch | |---------+ host 3 |
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| | | | +---------------+ | | |
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| +----------------+ | | +-------------+
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| +----------------+ | |----------+ host 4 |
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| | serial console +---------------------------------| | |
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| | mux switch | | | +------------+
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| +----------------+ | | +-----------+
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| | +-----------| BMC |
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+---------------------------+ +-----------+
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```
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There are two additional hardware buttons/switch available in the frontpanel for
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yv2.
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## 1.Host selector switch (selector switch)
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This host selector switch/selector switch has 4 gpio connected as input and
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based on the gpio state values the host selector switch value is derived. The
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possible switch values can vary from 0 to 10. The specific mapping between gpio
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values and host selector values can be stored as part of gpio json config.
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yosemiteV2 platform has 1 bmc and 4 hosts and only one power button and reset
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button.
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For example, when the power button is pressed, The value of the host selector
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switch position(1 to 10) decides whether the power button action is needs to be
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triggered for bmc or any one of the hosts.
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This option is to use same power button and reset button for multiple hosts.
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The power/reset button press events are triggered based on the value of host
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selector switch position.
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### Example :
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host selector position value = 0,bmc is mapped to power and reset buttons host
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selector position value = 1,host 1 is mapped to power and reset buttons host
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selector position value = 2,host 2 is mapped to power and reset buttons host
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selector position value = 3,host 3 is mapped to power and reset buttons host
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selector position value = 4,host 4 is mapped to power and reset buttons
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## 2.Serial console MUX switch
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There is also uart console for each host and bmc which is connected via a MUX
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switch.
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At a time any one of the device (either bmc or any one host) can be accessed via
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the console which is based on the UART MUX switch configuration.
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Based on the position of the host selector switch, a separate handler interface
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can configure the respective serial console device is selected.
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## 3.OCP debug card host selector button
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An OCP debug card can be connected to yosemitev2 via usb for debugging purpose.
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This is a extension which has three buttons : 1.Power button 2.reset button
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3.host selector button
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Power and reset buttons are mapped to the same gpio of frontpanel so no separate
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event handling is required.
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The host selector button purpose is same as that of the front panel host
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selector switch in yosemitev2 front panel. The debug card host selector button
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(push button) has different gpio lines than that of front panel host selector
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switch gpios. Whenever the debug host selector button is pressed the host
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selector switch position value should be increased up to MaxPosition. If the
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host selector switch value is more than MaxPosition then it should be reset to
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zero.
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# Proposed Design
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Three high level changes are required in the phosphor button interface class
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1. Add support for adding button interfaces which are monitoring more than one
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gpio event and process with single event handler.
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2. Add support to monitor button / switch interface event based on dbus property
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changes (needed for serial console MUX).
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3. Each button interface class can be extended with the following overridable
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methods to allow platform specific logic if needed in a derived class.
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- init() - This method may have gpio configuration and event handler
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initialization.
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- handleEvent() - This method may have custom event handling routines for the
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respective button interface.This should be be called from the main even
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handler function.
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## The host selector switch interface
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The host selector switch has 4 gpios associated with it. host selector switch
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button interface monitors these 4 gpio io events as sd-event based event loop
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and a single event handler function is called for all 4 gpio events.
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Based on the 4 gpio state values, the host selector switch position value is
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derived and stored as a dbus property with name "Position".
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### Host selector dbus interface details
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1. Position(property) - This is the property which holds the current value of
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the host selector switch based on the GPIO state.
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2. MaxPosition(property) - This is the property which keeps the maximum number
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of Position the Position property can hold.(This value is based on the number
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of hosts available in the platform)
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## OCP Debug card host selector button interface
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A separate interface for debug card host selector button is created.
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This button interface monitors the corresponding gpio lines for debug card host
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selection button press and release event via sd-event based loop.
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### OCP Debug card host selector button dbus interface details :
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1. Released(signal) - This is signal is triggered in the ocp debug card event
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handler when the ocp debug card button is pressed and released.
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When the event handler is called once the button is released, then the host
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selector switch dbus property "Position" is increased by 1. The host selector
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switch dbus property value is rollover to zero after Position value exceeds
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MaxPosition Value.
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This way when power and reset button press events are handled, the Host selector
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Position property is referred and based on the Position respective power events
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are called.
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## serial console MUX interface
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This button interface monitors for change in host selector switch Position dbus
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property and based on the dbus property value change, corresponding serial
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console is selected.mux value can be set as configuring 4 gpio lines dedicated
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for the serial console mux.
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### Example
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0 - bmc serial console 1 - host 1 serial console 2 - host 2 serial console 3 -
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host 3 serial console 4 - host 4 serial console
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### Change in power button and reset button interface event handler
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If selector button instance is available,then the power button and reset button
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pressed events must route to appropriate multihost dbus service name
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## Impacts
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The change impacts are under phosphor buttons repo,the existing power and reset
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button handlers are calling dbus calls for single host power events. This calls
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should be modified to adapt corresponding multi host power events and the
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respective host dbus object is based on host selector position.
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## Testing
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The proposed design can be tested in a platform in which the multiple hosts are
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connected.
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