[Skiboot] [PATCH] i2c: Fix i2c request hang during opal init if timers are not checked

[Frederic Barrat]

If an i2c request cannot go through the first time, because the bus is
found in error and need a reset or it's locked by the OCC for example,
the underlying i2c implementation is using timers to manage the
request. However during opal init, opal pollers may not be called, it
depends in the context in which the i2c request is made. If the
pollers are not called, the timers are not checked and we can end up
with an i2c request which will not move foward and skiboot hangs.

Fix it by explicitly checking the timers if we are waiting for an i2c
request to complete and it seems to be taking a while.

Signed-off-by: Frederic Barrat <fbarrat at linux.ibm.com>
---
 core/i2c.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/core/i2c.c b/core/i2c.c
index 26926fc2..3c600024 100644
--- a/core/i2c.c
+++ b/core/i2c.c
@@ -21,6 +21,7 @@
 #include <opal-msg.h>
 #include <timebase.h>
 #include <processor.h>
+#include <timer.h>
 
 static LIST_HEAD(i2c_bus_list);
 
@@ -177,6 +178,7 @@ int i2c_request_send(int bus_id, int dev_addr, int read_write,
 	struct i2c_bus *bus;
 	uint64_t time_to_wait = 0;
 	struct i2c_sync_userdata ud;
+	uint64_t timer_period = msecs_to_tb(5), timer_count;
 
 	bus = i2c_find_bus_by_id(bus_id);
 	if (!bus) {
@@ -215,6 +217,7 @@ int i2c_request_send(int bus_id, int dev_addr, int read_write,
 
 	for (retries = 0; retries <= MAX_NACK_RETRIES; retries++) {
 		waited = 0;
+		timer_count = 0;
 
 		i2c_queue_req(req);
 
@@ -224,6 +227,19 @@ int i2c_request_send(int bus_id, int dev_addr, int read_write,
 				time_to_wait = REQ_COMPLETE_POLLING;
 			time_wait(time_to_wait);
 			waited += time_to_wait;
+			timer_count += time_to_wait;
+			if (timer_count > timer_period) {
+				/*
+				 * The above request may be relying on
+				 * timers to complete, yet there may
+				 * not be called, especially during
+				 * opal init. We could be looping here
+				 * forever. So explicitly check the
+				 * timers once in a while
+				 */
+				check_timers(false);
+				timer_count = 0;
+			}
 		} while (!ud.done);
 
 		lwsync();
-- 
2.19.1