ipmi:msghandler: retry to get device id on an error

We fail to get the BMCS's device id with low probability when loading
the ipmi driver and it causes BMC device registration failed. When this
issue occurs we got below kernel prints:

[Wed Sep 9 19:52:03 2020] ipmi_si IPI0001:00: IPMI message handler:
device id demangle failed: -22
[Wed Sep 9 19:52:03 2020] IPMI BT: using default values
[Wed Sep 9 19:52:03 2020] IPMI BT: req2rsp=5 secs retries=2
[Wed Sep 9 19:52:03 2020] ipmi_si IPI0001:00: Unable to get the
device id: -5
[Wed Sep 9 19:52:04 2020] ipmi_si IPI0001:00: Unable to register
device: error -5

When this issue happens, we want to manually unload the driver and try to
load it again, but it can't be unloaded by 'rmmod' as it is already 'in
use'.

We add a print in handle_one_recv_msg(), when this issue happens,
the msg we received is "Recv: 1c 01 d5", which means the data_len is 1,
data[0] is 0xd5 (completion code), which means "bmc cannot execute
command. Command, or request parameter(s), not supported in present
state". Debug code:
static int handle_one_recv_msg(struct ipmi_smi *intf,
struct ipmi_smi_msg *msg) {
printk("Recv: %*ph\n", msg->rsp_size, msg->rsp);
... ...
}
Then in ipmi_demangle_device_id(), it returned '-EINVAL' as 'data_len < 7'
and 'data[0] != 0'.

We created this patch to retry the get device id when this error
happens. We reproduced this issue again and the retry succeed on the
first retry, we finally got the correct msg and then all is ok:
Recv: 1c 01 00 01 81 05 84 02 af db 07 00 01 00 b9 00 10 00

So use a retry machanism in this patch to give bmc more opportunity to
correctly response kernel when we received specific completion codes.

Signed-off-by: Xianting Tian <[e-mail]>
Message-Id: <[e-mail]>
[Cleaned up the verbage a bit in the header and prints.]
Signed-off-by: Corey Minyard <[e-mail]>

drivers/char/ipmi/ipmi_msghandler.c

···
 #include <linux/uuid.h>
 #include <linux/nospec.h>
 #include <linux/vmalloc.h>
+#include <linux/delay.h>
 
 #define IPMI_DRIVER_VERSION "39.2"
 
···
 #else
 #define IPMI_PANIC_DEFAULT IPMI_SEND_PANIC_EVENT_NONE
 #endif
+
+#define GET_DEVICE_ID_MAX_RETRY	5
+
 static enum ipmi_panic_event_op ipmi_send_panic_event = IPMI_PANIC_DEFAULT;
 
 static int panic_op_write_handler(const char *val,
···
 	int                    dyn_guid_set;
 	struct kref	       usecount;
 	struct work_struct     remove_work;
+	char		       cc; /* completion code */
 };
 #define to_bmc_device(x) container_of((x), struct bmc_device, pdev.dev)
 
···
 			msg->msg.data, msg->msg.data_len, &intf->bmc->fetch_id);
 	if (rv) {
 		dev_warn(intf->si_dev, "device id demangle failed: %d\n", rv);
+		/* record completion code when error */
+		intf->bmc->cc = msg->msg.data[0];
 		intf->bmc->dyn_id_set = 0;
 	} else {
 		/*
···
 static int __get_device_id(struct ipmi_smi *intf, struct bmc_device *bmc)
 {
 	int rv;
-
-	bmc->dyn_id_set = 2;
+	unsigned int retry_count = 0;
 
 	intf->null_user_handler = bmc_device_id_handler;
+
+retry:
+	bmc->cc = 0;
+	bmc->dyn_id_set = 2;
 
 	rv = send_get_device_id_cmd(intf);
 	if (rv)
···
 
 	wait_event(intf->waitq, bmc->dyn_id_set != 2);
 
-	if (!bmc->dyn_id_set)
+	if (!bmc->dyn_id_set) {
+		if ((bmc->cc == IPMI_DEVICE_IN_FW_UPDATE_ERR
+		     || bmc->cc ==  IPMI_DEVICE_IN_INIT_ERR
+		     || bmc->cc ==  IPMI_NOT_IN_MY_STATE_ERR)
+		     && ++retry_count <= GET_DEVICE_ID_MAX_RETRY) {
+			msleep(500);
+			dev_warn(intf->si_dev,
+			    "BMC returned 0x%2.2x, retry get bmc device id\n",
+			    bmc->cc);
+			goto retry;
+		}
+
 		rv = -EIO; /* Something went wrong in the fetch. */
+	}
 
 	/* dyn_id_set makes the id data available. */
 	smp_rmb();
···
 		/* It's the one we want */
 		if (msg->msg.data[0] != 0) {
 			/* Got an error from the channel, just go on. */
-
 			if (msg->msg.data[0] == IPMI_INVALID_COMMAND_ERR) {
 				/*
 				 * If the MC does not support this

include/uapi/linux/ipmi_msgdefs.h

···
 #define IPMI_ERR_MSG_TRUNCATED		0xc6
 #define IPMI_REQ_LEN_INVALID_ERR	0xc7
 #define IPMI_REQ_LEN_EXCEEDED_ERR	0xc8
+#define IPMI_DEVICE_IN_FW_UPDATE_ERR	0xd1
+#define IPMI_DEVICE_IN_INIT_ERR		0xd2
 #define IPMI_NOT_IN_MY_STATE_ERR	0xd5	/* IPMI 2.0 */
 #define IPMI_LOST_ARBITRATION_ERR	0x81
 #define IPMI_BUS_ERR			0x82