[PATCH net v3] net: amd-xgbe: discard rx packets with bad FCS

[James Nugraha <aslan.jnn@gmail.com>]

amd-xgbe driver currently sets the MAC_RCR.DCRCC bit whenever
RX is enabled. This disables hardware FCS validation, causing packets
with bad FCS to be accepted unconditionally.

This change unsets DCRCC so that packets with bad FCS will be dropped,
in-line with typical behaviours of many other network controllers.

Tests:
- Verified that packets with bad FCS are now dropped.
- Verified that receiving packets with bad FCS will increment the
  `rx_crc_errors` counter.

Fixes: c5aa9e3b8156 ("amd-xgbe: Initial AMD 10GbE platform driver")
Signed-off-by: James Nugraha <aslan.jnn@gmail.com>
---
v3:
  - Removed DCRCC unset on xgbe_disable_rx().
  - Add back the missing "Fixes" reference.
v2: https://lore.kernel.org/all/20260819091656.23943-1-aslan.jnn@gmail.com/
  - Eliminated DCRCC toggling via RXALL: now it simply sets the
    correct default value on MAC Rx enable.
  - Updated testing information.
v1: https://lore.kernel.org/all/20260812091616.35811-1-aslan.jnn@gmail.com/

 drivers/net/ethernet/amd/xgbe/xgbe-dev.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-dev.c b/drivers/net/ethernet/amd/xgbe/xgbe-dev.c
index 2de974213..e2e850c1b 100644
--- a/drivers/net/ethernet/amd/xgbe/xgbe-dev.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-dev.c
@@ -3400,7 +3400,7 @@ static void xgbe_enable_rx(struct xgbe_prv_data *pdata)
 	XGMAC_IOWRITE(pdata, MAC_RQC0R, reg_val);
 
 	/* Enable MAC Rx */
-	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, DCRCC, 1);
+	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, DCRCC, 0);
 	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, CST, 1);
 	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, ACS, 1);
 	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, RE, 1);
@@ -3411,7 +3411,6 @@ static void xgbe_disable_rx(struct xgbe_prv_data *pdata)
 	unsigned int i;
 
 	/* Disable MAC Rx */
-	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, DCRCC, 0);
 	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, CST, 0);
 	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, ACS, 0);
 	XGMAC_IOWRITE_BITS(pdata, MAC_RCR, RE, 0);