net: stmmac: Fallback to Platform Data clock in Watchdog conversion

If we don't have DT then stmmac_clk will not be available. Let's add a
new Platform Data field so that we can specify the refclk by this mean.

This way we can still use the coalesce command in PCI based setups.
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c

@@ -721,8 +721,11 @@ static u32 stmmac_usec2riwt(u32 usec, struct stmmac_priv *priv)
 {
 	unsigned long clk = clk_get_rate(priv->plat->stmmac_clk);
 
+	if (!clk) {
+		clk = priv->plat->clk_ref_rate;
 		if (!clk)
 			return 0;
+	}
 
 	return (usec * (clk / 1000000)) / 256;
 }
@@ -731,8 +734,11 @@ static u32 stmmac_riwt2usec(u32 riwt, struct stmmac_priv *priv)
 {
 	unsigned long clk = clk_get_rate(priv->plat->stmmac_clk);
 
+	if (!clk) {
+		clk = priv->plat->clk_ref_rate;
 		if (!clk)
 			return 0;
+	}
 
 	return (riwt * 256) / (clk / 1000000);
 }

include/linux/stmmac.h

@@ -184,6 +184,7 @@ struct plat_stmmacenet_data {
 	struct clk *pclk;
 	struct clk *clk_ptp_ref;
 	unsigned int clk_ptp_rate;
+	unsigned int clk_ref_rate;
 	struct reset_control *stmmac_rst;
 	struct stmmac_axi *axi;
 	int has_gmac4;