drivers/net/airoha_eth: enable hw padding of short tx packets

Transmission of short packets does not work good for XFI (GDM2) and
HSGMII (GDM3) interfaces. The issue can be solved with:

 - padding of short packets to 60 bytes
 - setting of PAD_EN bit in the corresponding REG_GDM_FWD_CFG(n)
   register.

The issue should present for the lan switch (GDM1) as well, but it does
does not appear due to unknown reason.

This patch set PAD_EN bit for the used GDM.

Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@iopsys.eu>

diff --git a/drivers/net/airoha_eth.c b/drivers/net/airoha_eth.c
index 477a132fb1fc82da4900768c274027ec8dc4b7b4..6588eb3a8060081a012ca0a255d3b3ad26a6509c 100644 (file)
--- a/drivers/net/airoha_eth.c
+++ b/drivers/net/airoha_eth.c
@@ -97,6 +97,7 @@
         (_n) == 2 ? GDM2_BASE : GDM1_BASE)
 
 #define REG_GDM_FWD_CFG(_n)            GDM_BASE(_n)
+#define GDM_PAD_EN                     BIT(28)
 #define GDM_DROP_CRC_ERR               BIT(23)
 #define GDM_IP4_CKSUM                  BIT(22)
 #define GDM_TCP_CKSUM                  BIT(21)
@@ -380,8 +381,11 @@ static void airoha_fe_maccr_init(struct airoha_eth *eth)
        int p;
 
        for (p = 1; p <= ARRAY_SIZE(eth->ports); p++) {
-               /* Disable any kind of CRC drop or offload */
-               airoha_fe_wr(eth, REG_GDM_FWD_CFG(p), 0);
+               /*
+                * Disable any kind of CRC drop or offload.
+                * Enable padding of short TX packets to 60 bytes.
+                */
+               airoha_fe_wr(eth, REG_GDM_FWD_CFG(p), GDM_PAD_EN);
        }
 }
 
@@ -830,6 +834,11 @@ static int airoha_eth_send(struct udevice *dev, void *packet, int length)
        u32 val;
        int i;
 
+       /*
+        * There is no need to pad short TX packets to 60 bytes since the
+        * GDM_PAD_EN bit set in the corresponding REG_GDM_FWD_CFG(n) register.
+        */
+
        dma_addr = dma_map_single(packet, length, DMA_TO_DEVICE);
 
        qid = 0;