[PATCH v2 4/7] net: phy: add helper for mapping RGMII link speed to clock rate

["Jan Petrous (OSS)" <jan.petrous@xxxxxxxxxxx>]

The helper rgmii_clock() implemented Russel's hint during stmmac
glue driver review:

---
We seem to have multiple cases of very similar logic in lots of stmmac
platform drivers, and I think it's about time we said no more to this.
So, what I think we should do is as follows:

add the following helper - either in stmmac, or more generically
(phylib? - in which case its name will need changing.)

static long stmmac_get_rgmii_clock(int speed)
{
	switch (speed) {
	case SPEED_10:
		return 2500000;

	case SPEED_100:
		return 25000000;

	case SPEED_1000:
		return 125000000;

	default:
		return -ENVAL;
	}
}

Then, this can become:

	long tx_clk_rate;

	...

	tx_clk_rate = stmmac_get_rgmii_clock(speed);
	if (tx_clk_rate < 0) {
		dev_err(gmac->dev, "Unsupported/Invalid speed: %d\n", speed);
		return;
	}

	ret = clk_set_rate(gmac->tx_clk, tx_clk_rate);
---

Signed-off-by: Jan Petrous (OSS) <jan.petrous@xxxxxxxxxxx>
---
 include/linux/phy.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/include/linux/phy.h b/include/linux/phy.h
index 6b7d40d49129..bb797364d91c 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -298,6 +298,27 @@ static inline const char *phy_modes(phy_interface_t interface)
 	}
 }
 
+/**
+ * rgmi_clock - map link speed to the clock rate
+ * @speed: link speed value
+ *
+ * Description: maps RGMII supported link speeds
+ * into the clock rates.
+ */
+static inline long rgmii_clock(int speed)
+{
+	switch (speed) {
+	case SPEED_10:
+		return 2500000;
+	case SPEED_100:
+		return 25000000;
+	case SPEED_1000:
+		return 125000000;
+	default:
+		return -EINVAL;
+	}
+}
+
 #define PHY_INIT_TIMEOUT	100000
 #define PHY_FORCE_TIMEOUT	10
 
-- 
2.46.0