[PATCH v2] net: ravb: Fix RX error handling

[Marek Vasut]

Correctly handle RX errors in ravb_recv() by returning 0 instead
of -EAGAIN on RX error.

In case the RAVB driver detects an RX error in ravb_recv(), it must
not return the -EAGAIN, but instead must return 0. Both error codes
are handled in eth-uclass.c eth_rx() and -EAGAIN is rewritten to 0
at the end of eth_rx(), but negative return code from the .recv()
callback does not trigger .free_pkt() callback, which would clean
up and re-enqueue the descriptor which holds the currently received
corrupted packet. The .free_pkt() must be called for this descriptor,
otherwise the follow up received data become corrupted too, even if
those packets are correctly received. Returning 0 from the .recv()
callback assures the corrupted packet is not processed by the network
stack, but is skipped instead.

For TFTP loading, an RX error produces the timeout "T" output and
resumes the TFTP loading operation shortly afterward, without any
data corruption.

Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
---
Cc: Joe Hershberger <joe.hershberger at ni.com>
Cc: Nobuhiro Iwamatsu <iwamatsu at nigauri.org>
Cc: Paul Barker <paul.barker.ct at bp.renesas.com>
Cc: Ramon Fried <rfried.dev at gmail.com>
Cc: Tom Rini <trini at konsulko.com>
Cc: u-boot at lists.denx.de
---
V2: Always assign **packet pointer and always invalid the cache over it,
    even in case of an error. Avoid passing NULL packet pointer to the
    .free_pkt() callback.
---
 drivers/net/ravb.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ravb.c b/drivers/net/ravb.c
index 539fd37ee59..e1ce1d8957b 100644
--- a/drivers/net/ravb.c
+++ b/drivers/net/ravb.c
@@ -181,7 +181,7 @@ static int ravb_recv(struct udevice *dev, int flags, uchar **packetp)
 {
 	struct ravb_priv *eth = dev_get_priv(dev);
 	struct ravb_rxdesc *desc = &eth->rx_desc[eth->rx_desc_idx];
-	int len;
+	int len = 0;
 	u8 *packet;
 
 	/* Check if the rx descriptor is ready */
@@ -190,12 +190,11 @@ static int ravb_recv(struct udevice *dev, int flags, uchar **packetp)
 		return -EAGAIN;
 
 	/* Check for errors */
-	if (desc->data.ctrl & RAVB_RX_DESC_MSC_RX_ERR_MASK) {
+	if (desc->data.ctrl & RAVB_RX_DESC_MSC_RX_ERR_MASK)
 		desc->data.ctrl &= ~RAVB_RX_DESC_MSC_MASK;
-		return -EAGAIN;
-	}
+	else
+		len = desc->data.ctrl & RAVB_DESC_DS_MASK;
 
-	len = desc->data.ctrl & RAVB_DESC_DS_MASK;
 	packet = (u8 *)(uintptr_t)desc->data.dptr;
 	ravb_invalidate_dcache((uintptr_t)packet, len);
 
-- 
2.47.2