1# PSU firmware update
2
3Author: Lei YU <mine260309@gmail.com> <LeiYU>
4
5Other contributors: Su Xiao <suxiao@inspur.com> Derek Howard <derekh@us.ibm.com>
6
7Created: 2019-06-03
8
9## Problem Description
10
11There is no support in OpenBMC to update the firmware for PSUs.
12
13## Background and References
14
15In OpenBMC, there is an existing interface for [software update][1].
16
17The update process consists of:
18
191. Uploading an image to the BMC;
202. Processing the image to check the version and purpose of the image;
213. Verifying and activating the image.
22
23Currently, BMC and BIOS firmware update are supported:
24
25- [phosphor-bmc-code-mgmt][2] implements BMC code update, and it supports all
26  the above 3 processes.
27- [openpower-pnor-code-mgmt][3] implements BIOS code update, and it only
28  implements "verifying and activating" the image. It shares the function of the
29  above 1 & 2 processes.
30- Both of the above use the same [Software DBus interface][1].
31
32For PSU firmware update, it is preferred to re-use the same function for the
33above 1 & 2.
34
35## Requirements
36
37The PSU firmware shall be updated in the below cases:
38
391. The user manually invokes the APIs to do the update;
402. After BMC code update and if there is a newer PSU image in the BMC's
41   filesystem, BMC shall update the PSU firmware;
423. When a PSU is replaced and the version is older than the one in BMC's
43   filesystem, BMC shall update the PSU firmware.
444. There are cases that a system could use different models of PSUs, and thus
45   different PSU firmware images need to be supported.
46
47For some PSUs, it is risky to do PSU code update while the host is running to
48avoid power loss. This shall be handled by PSU vendor-specific tools, but not in
49the generic framework.
50
51Note: The "vendor-specific" referred below is the PSU vendor-specific.
52
53So the below checks are optional and expected to be handled by vendor-specific
54tool:
55
561. If the host is powered off;
572. If the redundant PSUs are all connected;
583. If the AC input and DC standby output is OK on all the PSUs;
59
60## Proposed Design
61
62As described in the above requirements, there are different cases where the PSU
63firmware is updated:
64
65- When the APIs are invoked;
66- When a new version is updated together with BMC code update;
67- When a PSU is replaced with an old version of the firmware.
68
69### Update by API
70
71This method is usually used by users who manually update PSU firmware.
72
73It will re-use the current interfaces to upload, verify, and activate the image.
74
751. The "Version" interface needs to be extended:
76   - Add a new [VersionPurpose][4] for PSU;
77   - Re-use the existing `ExtendedVersion` as an additional string for
78     vendor-specific purpose, e.g. to indicate the PSU model.
792. Re-use the existing functions implemented by [phosphor-bmc-code-mgmt][2] for
80   uploading and processing the image.
81   - The PSU update image shall be a tarball that consists of a MANIFEST,
82     images, and signatures.
83   - When the PSU image is uploaded and processed, a `VersionObject` shall be
84     created to indicate the version and its purpose.
853. There will be a new service that implements the [Activation][5] interface to
86   update the PSU firmware.
87   - The service will be started by default when BMC starts;
88   - On start, the service will check the PSU's existing firmware and create the
89     `Version` and `Activation` interfaces.
90   - The service shall watch the interface added on
91     `/xyz/openbmc_project/Software`.
92   - When a new object with PSU `VersionPurpose` is added, the service will
93     verify the signature of the image;
94   - The service shall check the `ExtendedVersion` to make sure the image
95     matches the PSU model.
96   - The service will have a configuration file to describe the PSU model and
97     its related vendor-specific tools.
98   - The service will find the matched vendor-specific tool to perform the code
99     update. For example, if a vendor specific tool `foo` is configured in
100     `psu-update@foo.service` which executes `foo psu.bin`, the service will
101     find the `psu-update@foo.service` and start it by systemd, which performs
102     the update.
103   - When the PSU code update is completed, an informational event log shall be
104     created.
105   - When the PSU code update is completed, the image, MANIFEST, and optionally
106     the signature will be saved to a pre-defined directory in read-write
107     filesystem for future use, in case a new PSU with old firmware is plugged.
1084. The vendor-specific tool shall run all the checks it needs to be run, before
109   and after the PSU update, and return a status to the above service to
110   indicate the result.
1115. When the vendor-specific tool returns errors, the PSU update will be aborted
112   and an error event log shall be created.
1136. During the update, the service shall set the related sensors to
114   non-functional, and when the update is done, it shall set the related sensors
115   back to functional.
116
117### Update by new BMC image
118
119When BMC is updated and a new version of PSU firmware is included, it shall be
120updated to the PSU. This will be done by the same service described above.
121
1221. On start, the service will check the PSU image, model and version in its
123   filesystem, compare with the ones in PSU hardware and decide if PSU firmware
124   update shall be performed.
1252. There could be two places containing the PSU images:
126   - The pre-defined directory in read-only filesystem, which is part of BMC
127     image.
128   - The other pre-defined directory in read-write filesystem, which is the
129     location for the saved PSU images by API update. Both places shall be
130     checked and a newer version will be selected to compare with the PSU
131     hardware.
1323. If PSU update is needed, the service will find the matched vendor-specific
133   tool to perform the code update.
1344. The following process will be the same as [Update by API].
135
136### Update on replaced PSU
137
138When a PSU is replaced, and the firmware version is older than the one in BMC
139filesystem, it shall be updated. This will be done by the same service described
140above.
141
1421. On start, the service will subscribe to the PropertiesChanged signal to the
143   PSU object path to monitor the PSU presence status. (Or maybe subscribe the
144   InterfacesAdded/Removed signal?)
1452. When a PSU's presence status is changed from false to true (or the
146   InterfacesAdded event occurs), the service will check the new PSU's model,
147   firmware version to decide if the firmware needs to be updated.
1483. If yes, the service will find the matched vendor-specific tool to perform the
149   code update.
1504. The following process will be the same as [Update by API].
151
152## Alternatives Considered
153
154### General implementation
155
156The PSU firmware update could be implemented by separated recipes that only call
157vendor-specific tools. It will be a bit simpler but loses the unified interface
158provided by OpenBMC's existing [software update interface][1], and thus it will
159become difficult to use a standard API to the PSU firmware update.
160
161### VersionPurpose
162
163It is possible to re-use the `VersionPurpose.Other` to represent the PSU image's
164version purpose. But that requires additional information about the image,
165otherwise, there is no way to tell if the image is for PSU, or CPLD, or other
166peripherals. A new `VersionPurpose.PSU` is more specific and makes it easier to
167implement and friendly for the user.
168
169### Additional string
170
171The design proposal uses `ExtendedVersion` as the additional string for
172vendor-specific purpose, e.g. to indicate the PSU model, so the implementation
173could check and compare if the image matches the PSU model. It is possible to
174make it optional or remove this additional string, then the implementation will
175not verify if the image matches the PSU. It could be OK if we trust the user who
176is uploading the correct image, especially the image shall be signed. But it is
177always risky in case the image does not match the PSU, and cause unintended
178damage if the incorrect PSU firmware is updated.
179
180## Impacts
181
182This design only introduces a new `VersionPurpose` enum into the dbus
183interfaces. The newly introduced PSU firmware update service will be a new
184service that implements existing [Activation][5] interface. There will be new
185configuration files for the service to:
186
187- Link the vendor specific tool with PSU models.
188- Get the sensors related to the PSU.
189- etc.
190
191So the impacts are minimal to existing systems.
192
193## Testing
194
195It requires the manual tests to verify the PSU code update process.
196
197- Verify the PSU code update is done on all PSUs successfully;
198- Verify the PSU code update will fail if the vendor-specific tool fails on
199  pre-condition check, of fails on updating PSU.
200- Verify the PSU code update is performed after a new BMC image is updated
201  containing a new version of PSU firmware.
202- Verify the PSU code update is performed after a PSU with old firmware is
203  plugged in.
204
205[1]:
206  https://github.com/openbmc/phosphor-dbus-interfaces/tree/master/yaml/xyz/openbmc_project/Software
207[2]: https://github.com/openbmc/phosphor-bmc-code-mgmt/
208[3]: https://github.com/openbmc/openpower-pnor-code-mgmt/
209[4]:
210  https://github.com/openbmc/phosphor-dbus-interfaces/blob/57b878d048f929643276f1bf7fdf750abc4bde8b/xyz/openbmc_project/Software/Version.interface.yaml#L14
211[5]:
212  https://github.com/openbmc/phosphor-dbus-interfaces/blob/master/yaml/xyz/openbmc_project/Software/Activation.interface.yaml
213