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[2/5] net: dsa: b53: fix max MTU for 1g switches

Message ID 20241004-b53_jumbo_fixes-v1-2-ce1e54aa7b3c@gmail.com (mailing list archive)
State Accepted
Commit 680a8217dc00dc7e7da57888b3c053289b60eb2b
Delegated to: Netdev Maintainers
Headers show
Series net: dsa: b53: assorted jumbo frame fixes | expand

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Context Check Description
netdev/series_format warning Target tree name not specified in the subject
netdev/tree_selection success Guessed tree name to be net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 6 this patch: 6
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 9 of 9 maintainers
netdev/build_clang success Errors and warnings before: 6 this patch: 6
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
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: 5 this patch: 5
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 23 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-10-06--15-00 (tests: 775)

Commit Message

Jonas Gorski Oct. 4, 2024, 8:47 a.m. UTC
JMS_MAX_SIZE is the ethernet frame length, not the MTU, which is payload
without ethernet headers.

According to the datasheets maximum supported frame length for most
gigabyte swithes is 9720 bytes, so convert that to the expected MTU when
using VLAN tagged frames.

Fixes: 6ae5834b983a ("net: dsa: b53: add MTU configuration support")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
---
 drivers/net/dsa/b53/b53_common.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Florian Fainelli Oct. 5, 2024, 3:38 a.m. UTC | #1
On 10/4/2024 1:47 AM, Jonas Gorski wrote:
> JMS_MAX_SIZE is the ethernet frame length, not the MTU, which is payload
> without ethernet headers.
> 
> According to the datasheets maximum supported frame length for most
> gigabyte swithes is 9720 bytes, so convert that to the expected MTU when
> using VLAN tagged frames.

Only if you need to resubmit:

s/gigabyte swithes/gigabit switches/g

> 
> Fixes: 6ae5834b983a ("net: dsa: b53: add MTU configuration support")
> Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
diff mbox series

Patch

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 57df00ad9dd4cedfe9e959ea779d48e3f8f36142..6fed3eb15ad9b257c6fc3da20ce91b5e7129884c 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -27,6 +27,7 @@ 
 #include <linux/phylink.h>
 #include <linux/etherdevice.h>
 #include <linux/if_bridge.h>
+#include <linux/if_vlan.h>
 #include <net/dsa.h>
 
 #include "b53_regs.h"
@@ -224,6 +225,8 @@  static const struct b53_mib_desc b53_mibs_58xx[] = {
 
 #define B53_MIBS_58XX_SIZE	ARRAY_SIZE(b53_mibs_58xx)
 
+#define B53_MAX_MTU		(9720 - ETH_HLEN - VLAN_HLEN - ETH_FCS_LEN)
+
 static int b53_do_vlan_op(struct b53_device *dev, u8 op)
 {
 	unsigned int i;
@@ -2267,7 +2270,7 @@  static int b53_change_mtu(struct dsa_switch *ds, int port, int mtu)
 
 static int b53_get_max_mtu(struct dsa_switch *ds, int port)
 {
-	return JMS_MAX_SIZE;
+	return B53_MAX_MTU;
 }
 
 static const struct phylink_mac_ops b53_phylink_mac_ops = {