[PATCH] net: zynq_gem: Add cache flush to zynq_gem_free_pkt

Michal Simek michal.simek at xilinx.com
Tue Feb 25 12:42:49 CET 2020

From: Ashok Reddy Soma <ashok.reddy.soma at xilinx.com>

Add cache flush to zynq_gem_free_pkt. This is necessary
because some net routines would modify this buffer in place.
The cache_invalidate in the zynq_gem_recv function would cause
the modifications to the buffer to overwrite the DMA from the GEM,
if cache coherency is not enabled in the GEM, the next time the
buffer is in use.

Flushing the cache when the buffer is no longer in use by the
net functions ensures that the GEM DMA is going to take place
into a clean buffer.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma at xilinx.com>
Signed-off-by: Michal Simek <michal.simek at xilinx.com>

 drivers/net/zynq_gem.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/zynq_gem.c b/drivers/net/zynq_gem.c
index 5f2f87d352c4..cfd14665a70d 100644
--- a/drivers/net/zynq_gem.c
+++ b/drivers/net/zynq_gem.c
@@ -578,6 +578,7 @@ static int zynq_gem_free_pkt(struct udevice *dev, uchar *packet, int length)
 	struct zynq_gem_priv *priv = dev_get_priv(dev);
 	struct emac_bd *current_bd = &priv->rx_bd[priv->rxbd_current];
 	struct emac_bd *first_bd;
+	dma_addr_t addr;
 	if (current_bd->status & ZYNQ_GEM_RXBUF_SOF_MASK) {
 		priv->rx_first_buf = priv->rxbd_current;
@@ -592,6 +593,17 @@ static int zynq_gem_free_pkt(struct udevice *dev, uchar *packet, int length)
 		first_bd->status = 0xF0000000;
+	/* Flush the cache for the packet as well */
+#if defined(CONFIG_PHYS_64BIT)
+	addr = (dma_addr_t)((current_bd->addr & ZYNQ_GEM_RXBUF_ADD_MASK)
+		| ((dma_addr_t)current_bd->addr_hi << 32));
+	addr = current_bd->addr & ZYNQ_GEM_RXBUF_ADD_MASK;
+	flush_dcache_range(addr, addr + roundup(PKTSIZE_ALIGN,
+	barrier();
 	if ((++priv->rxbd_current) >= RX_BUF)
 		priv->rxbd_current = 0;

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