[Skiboot] [PATCH stable 5.1.x 2/3] hw/xscom: Reset XSCOM engine after finite number of retries when busy
Vipin K Parashar
vipin at linux.vnet.ibm.com
Wed Jul 20 23:52:28 AEST 2016
OPAL retries XSCOM read/write operations forever till it succeeds.
This can cause XSCOM ops to hang forever when XSCOM engine remains
busy for some reason. Changed it to retry XSCOM operations only
XSCOM_BUSY_MAX_RETRIES number of times instead of retrying forever.
Also added logic to reset XSCOM engine after XSCOM_BUSY_RESET_THRESHOLD
number of retries to unblock it when it remains busy.
Cc: stable # 9c2d82394fd2 ("xscom: Return OPAL_WRONG_STATE on XSCOM ops..")
Signed-off-by: Vipin K Parashar <vipin at linux.vnet.ibm.com>
Signed-off-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <stewart at linux.vnet.ibm.com>
(cherry picked from commit e761222593a1ae932cddbc81239b6a7cd98ddb70)
Signed-off-by: Vipin K Parashar <vipin at linux.vnet.ibm.com>
---
hw/xscom.c | 74 +++++++++++++++++++++++++++++++++++++++++-------------
include/errorlog.h | 1 +
include/xscom.h | 6 +++++
3 files changed, 64 insertions(+), 17 deletions(-)
diff --git a/hw/xscom.c b/hw/xscom.c
index 84f72f5..2ba2b14 100644
--- a/hw/xscom.c
+++ b/hw/xscom.c
@@ -23,6 +23,7 @@
#include <centaur.h>
#include <errorlog.h>
#include <opal-api.h>
+#include <timebase.h>
/* Mask of bits to clear in HMER before an access */
#define HMER_CLR_MASK (~(SPR_HMER_XSCOM_FAIL | \
@@ -41,6 +42,10 @@ DEFINE_LOG_ENTRY(OPAL_RC_XSCOM_RESET, OPAL_PLATFORM_ERR_EVT, OPAL_XSCOM,
OPAL_CEC_HARDWARE, OPAL_PREDICTIVE_ERR_GENERAL,
OPAL_NA);
+DEFINE_LOG_ENTRY(OPAL_RC_XSCOM_BUSY, OPAL_PLATFORM_ERR_EVT, OPAL_XSCOM,
+ OPAL_CEC_HARDWARE, OPAL_PREDICTIVE_ERR_GENERAL,
+ OPAL_NA);
+
/* xscom details to trigger xstop */
static struct {
uint64_t addr;
@@ -118,18 +123,49 @@ static void xscom_reset(uint32_t gcid)
*/
}
-static int xscom_handle_error(uint64_t hmer, uint32_t gcid, uint32_t pcb_addr,
- bool is_write)
+static int64_t xscom_handle_error(uint64_t hmer, uint32_t gcid, uint32_t pcb_addr,
+ bool is_write, int64_t retries)
{
+ struct timespec ts;
unsigned int stat = GETFIELD(SPR_HMER_XSCOM_STATUS, hmer);
/* XXX Figure out error codes from doc and error
* recovery procedures
*/
switch(stat) {
- /* XSCOM blocked, just retry */
+ /*
+ * XSCOM engine is blocked, need to retry. Reset XSCOM engine
+ * after crossing retry threshold before retrying again.
+ */
case 1:
+ if (retries && !(retries % XSCOM_BUSY_RESET_THRESHOLD)) {
+ prlog(PR_NOTICE, "XSCOM: Busy even after %d retries, "
+ "resetting XSCOM now. Total retries = %lld\n",
+ XSCOM_BUSY_RESET_THRESHOLD, retries);
+ xscom_reset(gcid);
+
+ /*
+ * Its observed that sometimes immediate retry of
+ * XSCOM operation returns wrong data. Adding a
+ * delay for XSCOM reset to be effective. Delay of
+ * 10 ms is found to be working fine experimentally.
+ * FIXME: Replace 10ms delay by exact delay needed
+ * or other alternate method to confirm XSCOM reset
+ * completion, after checking from HW folks.
+ */
+ ts.tv_sec = 0;
+ ts.tv_nsec = 10 * 1000;
+ nanosleep_nopoll(&ts, NULL);
+ }
+
+ /* Log error if we have retried enough and its still busy */
+ if (retries == XSCOM_BUSY_MAX_RETRIES)
+ log_simple_error(&e_info(OPAL_RC_XSCOM_BUSY),
+ "XSCOM: %s-busy error gcid=0x%x pcb_addr=0x%x "
+ "stat=0x%x\n", is_write ? "write" : "read",
+ gcid, pcb_addr, stat);
return OPAL_BUSY;
+
/* CPU is asleep, don't retry */
case 2:
return OPAL_WRONG_STATE;
@@ -178,14 +214,14 @@ static bool xscom_gcid_ok(uint32_t gcid)
static int __xscom_read(uint32_t gcid, uint32_t pcb_addr, uint64_t *val)
{
uint64_t hmer;
- int64_t ret;
+ int64_t ret, retries;
if (!xscom_gcid_ok(gcid)) {
prerror("%s: invalid XSCOM gcid 0x%x\n", __func__, gcid);
return OPAL_PARAMETER;
}
- for (;;) {
+ for (retries = 0; retries <= XSCOM_BUSY_MAX_RETRIES; retries++) {
/* Clear status bits in HMER (HMER is special
* writing to it *ands* bits
*/
@@ -199,27 +235,29 @@ static int __xscom_read(uint32_t gcid, uint32_t pcb_addr, uint64_t *val)
/* Check for error */
if (!(hmer & SPR_HMER_XSCOM_FAIL))
- break;
+ return OPAL_SUCCESS;
/* Handle error and possibly eventually retry */
- ret = xscom_handle_error(hmer, gcid, pcb_addr, false);
- if (ret == OPAL_HARDWARE || ret == OPAL_WRONG_STATE)
- return ret;
+ ret = xscom_handle_error(hmer, gcid, pcb_addr, false, retries);
+ if (ret != OPAL_BUSY)
+ break;
}
- return OPAL_SUCCESS;
+
+ prerror("XSCOM: Read failed, ret = %lld\n", ret);
+ return ret;
}
static int __xscom_write(uint32_t gcid, uint32_t pcb_addr, uint64_t val)
{
uint64_t hmer;
- int64_t ret;
+ int64_t ret, retries = 0;
if (!xscom_gcid_ok(gcid)) {
prerror("%s: invalid XSCOM gcid 0x%x\n", __func__, gcid);
return OPAL_PARAMETER;
}
- for (;;) {
+ for (retries = 0; retries <= XSCOM_BUSY_MAX_RETRIES; retries++) {
/* Clear status bits in HMER (HMER is special
* writing to it *ands* bits
*/
@@ -233,14 +271,16 @@ static int __xscom_write(uint32_t gcid, uint32_t pcb_addr, uint64_t val)
/* Check for error */
if (!(hmer & SPR_HMER_XSCOM_FAIL))
- break;
+ return OPAL_SUCCESS;
/* Handle error and possibly eventually retry */
- ret = xscom_handle_error(hmer, gcid, pcb_addr, true);
- if (ret == OPAL_HARDWARE || ret == OPAL_WRONG_STATE)
- return ret;
+ ret = xscom_handle_error(hmer, gcid, pcb_addr, true, retries);
+ if (ret != OPAL_BUSY)
+ break;
}
- return OPAL_SUCCESS;
+
+ prerror("XSCOM: Write failed, ret = %lld\n", ret);
+ return ret;
}
/*
diff --git a/include/errorlog.h b/include/errorlog.h
index ed90dab..214aed2 100644
--- a/include/errorlog.h
+++ b/include/errorlog.h
@@ -275,6 +275,7 @@ enum opal_reasoncode {
OPAL_RC_XSCOM_RW = OPAL_XS | 0x10,
OPAL_RC_XSCOM_INDIRECT_RW = OPAL_XS | 0x11,
OPAL_RC_XSCOM_RESET = OPAL_XS | 0x12,
+ OPAL_RC_XSCOM_BUSY = OPAL_XS | 0x13,
/* PCI */
OPAL_RC_PCI_INIT_SLOT = OPAL_PC | 0x10,
OPAL_RC_PCI_ADD_SLOT = OPAL_PC | 0x11,
diff --git a/include/xscom.h b/include/xscom.h
index 933af6a..1aee40e 100644
--- a/include/xscom.h
+++ b/include/xscom.h
@@ -167,6 +167,12 @@
/* HB folks say: try 10 time for now */
#define XSCOM_IND_MAX_RETRIES 10
+/* Max number of retries when XSCOM remains busy */
+#define XSCOM_BUSY_MAX_RETRIES 3000
+
+/* Retry count after which to reset XSCOM, if still busy */
+#define XSCOM_BUSY_RESET_THRESHOLD 1000
+
/*
* Error handling:
*
--
2.7.4
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