karo: tx51: justify and adjust the delay required before releasing the ETN PHY strap...

diff --git a/board/karo/tx51/tx51.c b/board/karo/tx51/tx51.c
index b94e537212b3f04a842d09741b718ecea526c48e..f8b8c3ffd506a54c7e75e99907984e0089726ab2 100644 (file)
--- a/board/karo/tx51/tx51.c
+++ b/board/karo/tx51/tx51.c
@@ -476,10 +476,12 @@ int board_eth_init(bd_t *bis)
        /* Deassert RESET to the external phy */
        gpio_set_value(TX51_FEC_RST_GPIO, 1);
 
-       /* Without this delay the PHY won't work, though nothing in
-        * the datasheets suggests that it should be necessary!
+       /*
+        * Due to an RC-filter in the PHY RESET line, a minimum
+        * delay of 535us is required to let the RESET line rise
+        * above the logic high threshold of the PHY input pin.
         */
-       udelay(400);
+       udelay(550);
        imx_iomux_v3_setup_multiple_pads(tx51_fec_pads,
                                        ARRAY_SIZE(tx51_fec_pads));