Re: [PATCH net-next 5/8] net: dsa: microchip: Add KSZ8463 tail tag handling
From: Simon Horman <horms@kernel.org>
Date: 2026-01-20 17:17:35
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On Thu, Jan 15, 2026 at 04:57:04PM +0100, Bastien Curutchet (Schneider Electric) wrote:
KSZ8463 uses the KSZ9893 DSA TAG driver. However, the KSZ8463 doesn't use the tail tag to convey timestamps to the host as KSZ9893 does. It uses the reserved fields in the PTP header instead. Add a KSZ8463-specifig DSA_TAG driver to handle KSZ8463 timestamps. There is no information in the tail tag to distinguish PTP packets from others so use the ptp_classify_raw() helper to find the PTP packets and extract the timestamp from their PTP headers. Signed-off-by: Bastien Curutchet (Schneider Electric) <redacted>
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quoted hunk ↗ jump to hunk
diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c index 9170a0148cc43b4213ec4bd8e81d338589671f23..635679402f8a96b29536a91988346a8825bae976 100644 --- a/net/dsa/tag_ksz.c +++ b/net/dsa/tag_ksz.c@@ -16,6 +16,7 @@ #define KSZ9477_NAME "ksz9477" #define KSZ9893_NAME "ksz9893" #define LAN937X_NAME "lan937x" +#define KSZ8463_NAME "ksz8463" /* Typically only one byte is used for tail tag. */ #define KSZ_PTP_TAG_LEN 4@@ -383,6 +384,108 @@ static const struct dsa_device_ops ksz9893_netdev_ops = { DSA_TAG_DRIVER(ksz9893_netdev_ops); MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893, KSZ9893_NAME); +#define KSZ8463_TAIL_TAG_PRIO GENMASK(4, 3) +#define KSZ8463_TAIL_TAG_EG_PORT_M GENMASK(2, 0) + +static void ksz8463_xmit_timestamp(struct dsa_port *dp, struct sk_buff *skb) +{ + struct ksz_tagger_private *priv; + struct ptp_header *ptp_hdr; + unsigned int ptp_type; + u32 tstamp_raw = 0; + s64 correction; + + priv = ksz_tagger_private(dp->ds); + + if (!test_bit(KSZ_HWTS_EN, &priv->state)) + return; + + if (!KSZ_SKB_CB(skb)->update_correction) + return; + + ptp_type = KSZ_SKB_CB(skb)->ptp_type; + ptp_hdr = ptp_parse_header(skb, ptp_type); + if (!ptp_hdr) + return; + + correction = (s64)get_unaligned_be64(&ptp_hdr->correction); + + if (correction < 0) { + struct timespec64 ts; + + ts = ns_to_timespec64(-correction >> 16); + tstamp_raw = ((ts.tv_sec & 3) << 30) | ts.tv_nsec; + + ptp_hdr->reserved2 = tstamp_raw;
I think that you need to assign a be32 rather than a u32 to reserved2.
Flagged by Sparse [1].
[1] This particular commit, from Al Viro's tree:
https://git.kernel.org/pub/scm/linux/kernel/git/viro/sparse.git/commit/?id=2634e39bf02697a18fece057208150362c985992
To address this mess:
https://lore.kernel.org/all/bf5b9a62-a120-421e-908d-1404c42e0b60@kernel.org/ (local)
+ } +}
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