[Skiboot] [PATCH] i2c: Fix i2c request hang during opal init if timers are not checked
Andrew Donnellan
andrew.donnellan at au1.ibm.com
Fri Nov 30 17:04:24 AEDT 2018
On 30/11/18 5:17 am, Frederic Barrat wrote:
> 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>
This seems like a reasonable solution.
Do we want this to go to stable?
Reviewed-by: Andrew Donnellan <andrew.donnellan at au1.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();
>
--
Andrew Donnellan OzLabs, ADL Canberra
andrew.donnellan at au1.ibm.com IBM Australia Limited
More information about the Skiboot
mailing list