net: dsa: sja1105: serialize access to the dynamic config interface

The sja1105 hardware seems as concurrent as can be, but when we create a
background script that adds/removes a rain of FDB entries without the
rtnl_mutex taken, then in parallel we do another operation like run
'bridge fdb show', we can notice these errors popping up:

sja1105 spi2.0: port 2 failed to read back entry for 00:01:02:03:00:40 vid 0: -ENOENT
sja1105 spi2.0: port 2 failed to add 00:01:02:03:00:40 vid 0 to fdb: -2
sja1105 spi2.0: port 2 failed to read back entry for 00:01:02:03:00:46 vid 0: -ENOENT
sja1105 spi2.0: port 2 failed to add 00:01:02:03:00:46 vid 0 to fdb: -2

Luckily what is going on does not require a major rework in the driver.
The sja1105_dynamic_config_read() function sends multiple SPI buffers to
the peripheral until the operation completes. We should not do anything
until the hardware clears the VALID bit.

But since there is no locking (i.e. right now we are implicitly
serialized by the rtnl_mutex, but if we remove that), it might be
possible that the process which performs the dynamic config read is
preempted and another one performs a dynamic config write.

What will happen in that case is that sja1105_dynamic_config_read(),
when it resumes, expects to see VALIDENT set for the entry it reads
back. But it won't.

This can be corrected by introducing a mutex for serializing SPI
accesses to the dynamic config interface which should be atomic with
respect to each other.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/dsa/sja1105/sja1105.h b/drivers/net/dsa/sja1105/sja1105.h
index 808419f3b808aedeffcb438f0da13c8226fe2ab8..21dba16af09793ad19a26dc285ff65ab3660fef2 100644 (file)
--- a/drivers/net/dsa/sja1105/sja1105.h
+++ b/drivers/net/dsa/sja1105/sja1105.h
@@ -261,6 +261,8 @@ struct sja1105_private {
         * the switch doesn't confuse them with one another.
         */
        struct mutex mgmt_lock;
+       /* Serializes access to the dynamic config interface */
+       struct mutex dynamic_config_lock;
        struct devlink_region **regions;
        struct sja1105_cbs_entry *cbs;
        struct mii_bus *mdio_base_t1;

diff --git a/drivers/net/dsa/sja1105/sja1105_dynamic_config.c b/drivers/net/dsa/sja1105/sja1105_dynamic_config.c
index 32ec34f181dedd3ad7f64787ba7084d6f8226e5e..7729d3f8b7f50a1a8fd85f1b5f34381817228812 100644 (file)
--- a/drivers/net/dsa/sja1105/sja1105_dynamic_config.c
+++ b/drivers/net/dsa/sja1105/sja1105_dynamic_config.c
@@ -1283,12 +1283,16 @@ int sja1105_dynamic_config_read(struct sja1105_private *priv,
                ops->entry_packing(packed_buf, entry, PACK);
 
        /* Send SPI write operation: read config table entry */
+       mutex_lock(&priv->dynamic_config_lock);
        rc = sja1105_xfer_buf(priv, SPI_WRITE, ops->addr, packed_buf,
                              ops->packed_size);
-       if (rc < 0)
+       if (rc < 0) {
+               mutex_unlock(&priv->dynamic_config_lock);
                return rc;
+       }
 
        rc = sja1105_dynamic_config_wait_complete(priv, &cmd, ops);
+       mutex_unlock(&priv->dynamic_config_lock);
        if (rc < 0)
                return rc;
 
@@ -1349,12 +1353,16 @@ int sja1105_dynamic_config_write(struct sja1105_private *priv,
                ops->entry_packing(packed_buf, entry, PACK);
 
        /* Send SPI write operation: read config table entry */
+       mutex_lock(&priv->dynamic_config_lock);
        rc = sja1105_xfer_buf(priv, SPI_WRITE, ops->addr, packed_buf,
                              ops->packed_size);
-       if (rc < 0)
+       if (rc < 0) {
+               mutex_unlock(&priv->dynamic_config_lock);
                return rc;
+       }
 
        rc = sja1105_dynamic_config_wait_complete(priv, &cmd, ops);
+       mutex_unlock(&priv->dynamic_config_lock);
        if (rc < 0)
                return rc;
 

diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index ef46ae53ab56f82497716cd2e9b29d5e254b834b..c343effe2e967a84ce441fb5ce58b70bc2493f72 100644 (file)
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -3365,6 +3365,7 @@ static int sja1105_probe(struct spi_device *spi)
        priv->ds = ds;
 
        mutex_init(&priv->ptp_data.lock);
+       mutex_init(&priv->dynamic_config_lock);
        mutex_init(&priv->mgmt_lock);
 
        rc = sja1105_parse_dt(priv);