net: ftgmac100: Request clock and set speed

According to the ASPEED datasheet, gigabit speeds require a clock of
100MHz or higher. Other speeds require 25MHz or higher. This patch
configures a 100MHz clock if the system has a direct-attached
PHY, or 25MHz if the system is running NC-SI which is limited to 100MHz.

There appear to be no other upstream users of the FTGMAC100 driver it is
hard to know the clocking requirements of other platforms. Therefore a
conservative approach was taken with enabling clocks. If the platform is
not ASPEED, both requesting the clock and configuring the speed is
skipped.
Signed-off-by: Joel Stanley <joel@jms.id.au>
Tested-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/faraday/ftgmac100.c

@@ -21,6 +21,7 @@
 
 #define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
 
+#include <linux/clk.h>
 #include <linux/dma-mapping.h>
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>
@@ -59,6 +60,9 @@
 /* Min number of tx ring entries before stopping queue */
 #define TX_THRESHOLD		(MAX_SKB_FRAGS + 1)
 
+#define FTGMAC_100MHZ		100000000
+#define FTGMAC_25MHZ		25000000
+
 struct ftgmac100 {
 	/* Registers */
 	struct resource *res;
@@ -96,6 +100,7 @@ struct ftgmac100 {
 	struct napi_struct napi;
 	struct work_struct reset_task;
 	struct mii_bus *mii_bus;
+	struct clk *clk;
 
 	/* Link management */
 	int cur_speed;
@@ -1734,6 +1739,22 @@ static void ftgmac100_ncsi_handler(struct ncsi_dev *nd)
 		    nd->link_up ? "up" : "down");
 }
 
+static void ftgmac100_setup_clk(struct ftgmac100 *priv)
+{
+	priv->clk = devm_clk_get(priv->dev, NULL);
+	if (IS_ERR(priv->clk))
+		return;
+
+	clk_prepare_enable(priv->clk);
+
+	/* Aspeed specifies a 100MHz clock is required for up to
+	 * 1000Mbit link speeds. As NCSI is limited to 100Mbit, 25MHz
+	 * is sufficient
+	 */
+	clk_set_rate(priv->clk, priv->use_ncsi ? FTGMAC_25MHZ :
+			FTGMAC_100MHZ);
+}
+
 static int ftgmac100_probe(struct platform_device *pdev)
 {
 	struct resource *res;
@@ -1830,6 +1851,9 @@ static int ftgmac100_probe(struct platform_device *pdev)
 			goto err_setup_mdio;
 	}
 
+	if (priv->is_aspeed)
+		ftgmac100_setup_clk(priv);
+
 	/* Default ring sizes */
 	priv->rx_q_entries = priv->new_rx_q_entries = DEF_RX_QUEUE_ENTRIES;
 	priv->tx_q_entries = priv->new_tx_q_entries = DEF_TX_QUEUE_ENTRIES;
@@ -1883,6 +1907,8 @@ static int ftgmac100_remove(struct platform_device *pdev)
 
 	unregister_netdev(netdev);
 
+	clk_disable_unprepare(priv->clk);
+
 	/* There's a small chance the reset task will have been re-queued,
 	 * during stop, make sure it's gone before we free the structure.
 	 */