diff mbox series

[3/3] net: dsa: qca8k: reset cpu port on MTU change

Message ID 20220618062300.28541-3-ansuelsmth@gmail.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series [1/3] net: dsa: qca8k: reduce mgmt ethernet timeout | expand

Checks

Context Check Description
netdev/tree_selection success Guessed tree name to be net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix warning Target tree name not specified in the subject
netdev/cover_letter warning Series does not have a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers success CCed 10 of 10 maintainers
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 39 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Christian Marangi June 18, 2022, 6:23 a.m. UTC 
It was discovered that the Documentation lacks of a fundamental detail
on how to correctly change the MAX_FRAME_SIZE of the switch.

In fact if the MAX_FRAME_SIZE is changed while the cpu port is on, the
switch panics and cease to send any packet. This cause the mgmt ethernet
system to not receive any packet (the slow fallback still works) and
makes the device not reachable. To recover from this a switch reset is
required.

To correctly handle this, turn off the cpu ports before changing the
MAX_FRAME_SIZE and turn on again after the value is applied.

Fixes: f58d2598cf70 ("net: dsa: qca8k: implement the port MTU callbacks")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/net/dsa/qca8k.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index eaaf80f96fa9..0b92b9d5954a 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c
@@ -2334,6 +2334,7 @@  static int
 qca8k_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
 {
 	struct qca8k_priv *priv = ds->priv;
+	int ret;
 
 	/* We have only have a general MTU setting.
 	 * DSA always set the CPU port's MTU to the largest MTU of the slave
@@ -2344,10 +2345,29 @@  qca8k_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
 	if (!dsa_is_cpu_port(ds, port))
 		return 0;
 
+	/* To change the MAX_FRAME_SIZE the cpu ports must be off or
+	 * the switch panics.
+	 * Turn off both cpu ports before applying the new value to prevent
+	 * this.
+	 */
+	if (priv->port_enabled_map & BIT(0))
+		qca8k_port_set_status(priv, 0, 0);
+
+	if (priv->port_enabled_map & BIT(6))
+		qca8k_port_set_status(priv, 6, 0);
+
 	/* Include L2 header / FCS length */
-	return regmap_update_bits(priv->regmap, QCA8K_MAX_FRAME_SIZE_REG,
-				  QCA8K_MAX_FRAME_SIZE_MASK,
-				  new_mtu + ETH_HLEN + ETH_FCS_LEN);
+	ret = regmap_update_bits(priv->regmap, QCA8K_MAX_FRAME_SIZE_REG,
+				 QCA8K_MAX_FRAME_SIZE_MASK,
+				 new_mtu + ETH_HLEN + ETH_FCS_LEN);
+
+	if (priv->port_enabled_map & BIT(0))
+		qca8k_port_set_status(priv, 0, 1);
+
+	if (priv->port_enabled_map & BIT(6))
+		qca8k_port_set_status(priv, 6, 1);
+
+	return ret;
 }
 
 static int