net: bcmgenet: test MPD_EN when resuming

When the GENET driver resumes from deep sleep the UMAC_CMD
register may not be accessible and therefore should not be
accessed from bcmgenet_wol_power_up_cfg() if the GENET has
been reset.

This commit adds a check of the MPD_EN flag when Wake on
Magic Packet is enabled. A clear flag indicates that the
GENET hardware must have been reset so the remainder of the
hardware programming is bypassed.

Fixes: 1a1d5106 ("net: bcmgenet: move clk_wol management to bcmgenet_wol")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/genet/bcmgenet_wol.c

@@ -217,11 +217,16 @@ void bcmgenet_wol_power_up_cfg(struct bcmgenet_priv *priv,
 
 	priv->wol_active = 0;
 	clk_disable_unprepare(priv->clk_wol);
+	priv->crc_fwd_en = 0;
 
 	/* Disable Magic Packet Detection */
+	if (priv->wolopts & (WAKE_MAGIC | WAKE_MAGICSECURE)) {
 		reg = bcmgenet_umac_readl(priv, UMAC_MPD_CTRL);
+		if (!(reg & MPD_EN))
+			return;	/* already reset so skip the rest */
 		reg &= ~(MPD_EN | MPD_PW_EN);
 		bcmgenet_umac_writel(priv, reg, UMAC_MPD_CTRL);
+	}
 
 	/* Disable WAKE_FILTER Detection */
 	reg = bcmgenet_hfb_reg_readl(priv, HFB_CTRL);
@@ -232,5 +237,4 @@ void bcmgenet_wol_power_up_cfg(struct bcmgenet_priv *priv,
 	reg = bcmgenet_umac_readl(priv, UMAC_CMD);
 	reg &= ~CMD_CRC_FWD;
 	bcmgenet_umac_writel(priv, reg, UMAC_CMD);
-	priv->crc_fwd_en = 0;
 }