There are two problems with WARN_ON() here. One: It is not ratelimited.
Two: We don't see which adapter was used when trying to transfer
something when already suspended. Implement a custom ratelimit once per
adapter and use dev_WARN there. This fixes both issues. Drawback is that
we don't see if multiple drivers are trying to transfer with the same
adapter while suspended. They need to be discovered one after the other
now. This is better than a high CPU load because a really broken driver
might try to resend endlessly.
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
---
So, Simon had a point with his review comment back then, and I think we now
found a properly balanced way. Tested with a Renesas Lager board (R-Car H2). I
decided against dev_WARN_ONCE because that seems too coarse grained for my
taste (once per system) and the custom implementation is small.
drivers/i2c/i2c-core-base.c | 5 ++++-
include/linux/i2c.h | 3 ++-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 4e6300dc2c4e..f8e85983cb04 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1867,8 +1867,11 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
if (WARN_ON(!msgs || num < 1))
return -EINVAL;
- if (WARN_ON(test_bit(I2C_ALF_IS_SUSPENDED, &adap->locked_flags)))
+ if (test_bit(I2C_ALF_IS_SUSPENDED, &adap->locked_flags)) {
+ if (!test_and_set_bit(I2C_ALF_SUSPEND_REPORTED, &adap->locked_flags))
+ dev_WARN(&adap->dev, "Transfer while suspended\n");
return -ESHUTDOWN;
+ }
if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))
return -EOPNOTSUPP;
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 03755d4c9229..be27062f8ed1 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -694,7 +694,8 @@ struct i2c_adapter {
int retries;
struct device dev; /* the adapter device */
unsigned long locked_flags; /* owned by the I2C core */
-#define I2C_ALF_IS_SUSPENDED 0
+#define I2C_ALF_IS_SUSPENDED 0
+#define I2C_ALF_SUSPEND_REPORTED 1
int nr;
char name[48];
--
2.11.0
