diff options
| author | Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> | 2025-10-17 16:18:30 +0100 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-10-22 18:15:14 -0700 |
| commit | 706136c5723626fcde8dd8f598a4dcd251e24927 (patch) | |
| tree | 046942f62337c8ec17658909d5cec4b2a0b82d1a | |
| parent | 5370c31e84b0e0999c7b5ff949f4e104def35584 (diff) | |
net: ravb: Ensure memory write completes before ringing TX doorbell
Add a final dma_wmb() barrier before triggering the transmit request
(TCCR_TSRQ) to ensure all descriptor and buffer writes are visible to
the DMA engine.
According to the hardware manual, a read-back operation is required
before writing to the doorbell register to guarantee completion of
previous writes. Instead of performing a dummy read, a dma_wmb() is
used to both enforce the same ordering semantics on the CPU side and
also to ensure completion of writes.
Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
Cc: stable@vger.kernel.org
Co-developed-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://patch.msgid.link/20251017151830.171062-5-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/net/ethernet/renesas/ravb_main.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c index 044ee83c63bb..e2d7ce1a85e8 100644 --- a/drivers/net/ethernet/renesas/ravb_main.c +++ b/drivers/net/ethernet/renesas/ravb_main.c @@ -2232,6 +2232,14 @@ static netdev_tx_t ravb_start_xmit(struct sk_buff *skb, struct net_device *ndev) dma_wmb(); desc->die_dt = DT_FSINGLE; } + + /* Before ringing the doorbell we need to make sure that the latest + * writes have been committed to memory, otherwise it could delay + * things until the doorbell is rang again. + * This is in replacement of the read operation mentioned in the HW + * manuals. + */ + dma_wmb(); ravb_modify(ndev, TCCR, TCCR_TSRQ0 << q, TCCR_TSRQ0 << q); priv->cur_tx[q] += num_tx_desc; |