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Date: Sat, 28 Dec 2019 15:30:45 +0200 From: Vladimir Oltean <olteanv@...il.com> To: davem@...emloft.net, jakub.kicinski@...ronome.com Cc: richardcochran@...il.com, f.fainelli@...il.com, vivien.didelot@...il.com, andrew@...n.ch, claudiu.manoil@....com, yangbo.lu@....com, netdev@...r.kernel.org, Vladimir Oltean <olteanv@...il.com> Subject: [PATCH v2 net 1/2] gianfar: Fix TX timestamping with a stacked DSA driver The driver wrongly assumes that it is the only entity that can set the SKBTX_IN_PROGRESS bit of the current skb. Therefore, in the gfar_clean_tx_ring function, where the TX timestamp is collected if necessary, the aforementioned bit is used to discriminate whether or not the TX timestamp should be delivered to the socket's error queue. But a stacked driver such as a DSA switch can also set the SKBTX_IN_PROGRESS bit, which is actually exactly what it should do in order to denote that the hardware timestamping process is undergoing. Therefore, gianfar would misinterpret the "in progress" bit as being its own, and deliver a second skb clone in the socket's error queue, completely throwing off a PTP process which is not expecting to receive it, _even though_ TX timestamping is not enabled for gianfar. There have been discussions [0] as to whether non-MAC drivers need or not to set SKBTX_IN_PROGRESS at all (whose purpose is to avoid sending 2 timestamps, a sw and a hw one, to applications which only expect one). But as of this patch, there are at least 2 PTP drivers that would break in conjunction with gianfar: the sja1105 DSA switch and the felix switch, by way of its ocelot core driver. So regardless of that conclusion, fix the gianfar driver to not do stuff based on flags set by others and not intended for it. [0]: https://www.spinics.net/lists/netdev/msg619699.html Fixes: f0ee7acfcdd4 ("gianfar: Add hardware TX timestamping support") Signed-off-by: Vladimir Oltean <olteanv@...il.com> Acked-by: Richard Cochran <richardcochran@...il.com> --- Changes from v1: - Reworded the commit message, dropped reference to the TI PHYTER. drivers/net/ethernet/freescale/gianfar.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c index 72868a28b621..7d08bf6370ae 100644 --- a/drivers/net/ethernet/freescale/gianfar.c +++ b/drivers/net/ethernet/freescale/gianfar.c @@ -2205,13 +2205,17 @@ static void gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue) skb_dirtytx = tx_queue->skb_dirtytx; while ((skb = tx_queue->tx_skbuff[skb_dirtytx])) { + bool do_tstamp; + + do_tstamp = (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) && + priv->hwts_tx_en; frags = skb_shinfo(skb)->nr_frags; /* When time stamping, one additional TxBD must be freed. * Also, we need to dma_unmap_single() the TxPAL. */ - if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS)) + if (unlikely(do_tstamp)) nr_txbds = frags + 2; else nr_txbds = frags + 1; @@ -2225,7 +2229,7 @@ static void gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue) (lstatus & BD_LENGTH_MASK)) break; - if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS)) { + if (unlikely(do_tstamp)) { next = next_txbd(bdp, base, tx_ring_size); buflen = be16_to_cpu(next->length) + GMAC_FCB_LEN + GMAC_TXPAL_LEN; @@ -2235,7 +2239,7 @@ static void gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue) dma_unmap_single(priv->dev, be32_to_cpu(bdp->bufPtr), buflen, DMA_TO_DEVICE); - if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS)) { + if (unlikely(do_tstamp)) { struct skb_shared_hwtstamps shhwtstamps; u64 *ns = (u64 *)(((uintptr_t)skb->data + 0x10) & ~0x7UL); -- 2.17.1
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