| 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586 |
- .. SPDX-License-Identifier: GPL-2.0
- ============================================
- AMD HSMP interface
- ============================================
- Newer Fam19h EPYC server line of processors from AMD support system
- management functionality via HSMP (Host System Management Port).
- The Host System Management Port (HSMP) is an interface to provide
- OS-level software with access to system management functions via a
- set of mailbox registers.
- More details on the interface can be found in chapter
- "7 Host System Management Port (HSMP)" of the family/model PPR
- Eg: https://www.amd.com/system/files/TechDocs/55898_B1_pub_0.50.zip
- HSMP interface is supported on EPYC server CPU models only.
- HSMP device
- ============================================
- amd_hsmp driver under the drivers/platforms/x86/ creates miscdevice
- /dev/hsmp to let user space programs run hsmp mailbox commands.
- $ ls -al /dev/hsmp
- crw-r--r-- 1 root root 10, 123 Jan 21 21:41 /dev/hsmp
- Characteristics of the dev node:
- * Write mode is used for running set/configure commands
- * Read mode is used for running get/status monitor commands
- Access restrictions:
- * Only root user is allowed to open the file in write mode.
- * The file can be opened in read mode by all the users.
- In-kernel integration:
- * Other subsystems in the kernel can use the exported transport
- function hsmp_send_message().
- * Locking across callers is taken care by the driver.
- An example
- ==========
- To access hsmp device from a C program.
- First, you need to include the headers::
- #include <linux/amd_hsmp.h>
- Which defines the supported messages/message IDs.
- Next thing, open the device file, as follows::
- int file;
- file = open("/dev/hsmp", O_RDWR);
- if (file < 0) {
- /* ERROR HANDLING; you can check errno to see what went wrong */
- exit(1);
- }
- The following IOCTL is defined:
- ``ioctl(file, HSMP_IOCTL_CMD, struct hsmp_message *msg)``
- The argument is a pointer to a::
- struct hsmp_message {
- __u32 msg_id; /* Message ID */
- __u16 num_args; /* Number of input argument words in message */
- __u16 response_sz; /* Number of expected output/response words */
- __u32 args[HSMP_MAX_MSG_LEN]; /* argument/response buffer */
- __u16 sock_ind; /* socket number */
- };
- The ioctl would return a non-zero on failure; you can read errno to see
- what happened. The transaction returns 0 on success.
- More details on the interface and message definitions can be found in chapter
- "7 Host System Management Port (HSMP)" of the respective family/model PPR
- eg: https://www.amd.com/system/files/TechDocs/55898_B1_pub_0.50.zip
- User space C-APIs are made available by linking against the esmi library,
- which is provided by the E-SMS project https://developer.amd.com/e-sms/.
- See: https://github.com/amd/esmi_ib_library
|
