[PATCH 5/6] net: dwc_eth_qos: Invalidate RX packet DMA buffer

Marek Vasut marex at denx.de
Mon Mar 23 02:45:25 CET 2020

This patch prevents an issue where the RX packet might have been
accessed by the CPU, which now has cached data from the packet in
the caches and possibly various write buffers, and these data may
be evicted from the caches into the DRAM while the buffer is also
written by the DMA.

By invalidating the buffer after the CPU accessed it and before the
DMA populates the buffer, it is assured that the buffer will not be

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Joe Hershberger <joe.hershberger at ni.com>
Cc: Patrice Chotard <patrice.chotard at st.com>
Cc: Patrick Delaunay <patrick.delaunay at st.com>
Cc: Ramon Fried <rfried.dev at gmail.com>
Cc: Stephen Warren <swarren at nvidia.com>
 drivers/net/dwc_eth_qos.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/dwc_eth_qos.c b/drivers/net/dwc_eth_qos.c
index e40c461278..7dadb10fe7 100644
--- a/drivers/net/dwc_eth_qos.c
+++ b/drivers/net/dwc_eth_qos.c
@@ -1430,6 +1430,9 @@ static int eqos_free_pkt(struct udevice *dev, uchar *packet, int length)
 	rx_desc = &(eqos->rx_descs[eqos->rx_desc_idx]);
+	eqos->config->ops->eqos_inval_buffer(packet, length);
 	rx_desc->des0 = (u32)(ulong)packet;
 	rx_desc->des1 = 0;
 	rx_desc->des2 = 0;
@@ -1492,6 +1495,9 @@ static int eqos_probe_resources_core(struct udevice *dev)
 	debug("%s: rx_pkt=%p\n", __func__, eqos->rx_pkt);
+	eqos->config->ops->eqos_inval_buffer(eqos->rx_dma_buf,
 	debug("%s: OK\n", __func__);
 	return 0;

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