stmmac: MDC clock dynamically based on the csr clock input

If a specific clk_csr value is passed from the platform
this means that the CSR Clock Range selection cannot be
changed at run-time and it is fixed (as reported in the driver
documentation). Viceversa the driver will try to set the MDC
clock dynamically according to the actual clock input.
Signed-off-by: Deepak Sikri <deepak.sikri@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Reviewed-by: Francesco Virlinzi <francesco.virlinzi@st.com>
Reviewed-by: David Laight <david.laight@aculab.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/stmmac.txt

@@ -137,7 +137,7 @@ Where:
  o pbl: the Programmable Burst Length is maximum number of beats to
        be transferred in one DMA transaction.
        GMAC also enables the 4xPBL by default.
- o clk_csr: CSR Clock range selection.
+ o clk_csr: fixed CSR Clock range selection.
  o has_gmac: uses the GMAC core.
  o enh_desc: if sets the MAC will use the enhanced descriptor structure.
  o tx_coe: core is able to perform the tx csum in HW.

drivers/net/ethernet/stmicro/stmmac/common.h

@@ -97,6 +97,16 @@ struct stmmac_extra_stats {
 	unsigned long normal_irq_n;
 };
 
+/* CSR Frequency Access Defines*/
+#define CSR_F_35M	35000000
+#define CSR_F_60M	60000000
+#define CSR_F_100M	100000000
+#define CSR_F_150M	150000000
+#define CSR_F_250M	250000000
+#define CSR_F_300M	300000000
+
+#define	MAC_CSR_H_FRQ_MASK	0x20
+
 #define HASH_TABLE_SIZE 64
 #define PAUSE_TIME 0x200
 

drivers/net/ethernet/stmicro/stmmac/stmmac.h

@@ -84,6 +84,7 @@ struct stmmac_priv {
 #ifdef CONFIG_HAVE_CLK
 	struct clk *stmmac_clk;
 #endif
+	int clk_csr;
 };
 
 extern int phyaddr;

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

@@ -163,6 +163,35 @@ static void stmmac_verify_args(void)
 		pause = PAUSE_TIME;
 }
 
+static void stmmac_clk_csr_set(struct stmmac_priv *priv)
+{
+#ifdef CONFIG_HAVE_CLK
+	u32 clk_rate;
+
+	clk_rate = clk_get_rate(priv->stmmac_clk);
+
+	/* Platform provided default clk_csr would be assumed valid
+	 * for all other cases except for the below mentioned ones. */
+	if (!(priv->clk_csr & MAC_CSR_H_FRQ_MASK)) {
+		if (clk_rate < CSR_F_35M)
+			priv->clk_csr = STMMAC_CSR_20_35M;
+		else if ((clk_rate >= CSR_F_35M) && (clk_rate < CSR_F_60M))
+			priv->clk_csr = STMMAC_CSR_35_60M;
+		else if ((clk_rate >= CSR_F_60M) && (clk_rate < CSR_F_100M))
+			priv->clk_csr = STMMAC_CSR_60_100M;
+		else if ((clk_rate >= CSR_F_100M) && (clk_rate < CSR_F_150M))
+			priv->clk_csr = STMMAC_CSR_100_150M;
+		else if ((clk_rate >= CSR_F_150M) && (clk_rate < CSR_F_250M))
+			priv->clk_csr = STMMAC_CSR_150_250M;
+		else if ((clk_rate >= CSR_F_250M) && (clk_rate < CSR_F_300M))
+			priv->clk_csr = STMMAC_CSR_250_300M;
+	} /* For values higher than the IEEE 802.3 specified frequency
+	   * we can not estimate the proper divider as it is not known
+	   * the frequency of clk_csr_i. So we do not change the default
+	   * divider. */
+#endif
+}
+
 #if defined(STMMAC_XMIT_DEBUG) || defined(STMMAC_RX_DEBUG)
 static void print_pkt(unsigned char *buf, int len)
 {
@@ -1890,6 +1919,17 @@ struct stmmac_priv *stmmac_dvr_probe(struct device *device,
 	if (stmmac_clk_get(priv))
 		goto error;
 
+	/* If a specific clk_csr value is passed from the platform
+	 * this means that the CSR Clock Range selection cannot be
+	 * changed at run-time and it is fixed. Viceversa the driver'll try to
+	 * set the MDC clock dynamically according to the csr actual
+	 * clock input.
+	 */
+	if (!priv->plat->clk_csr)
+		stmmac_clk_csr_set(priv);
+	else
+		priv->clk_csr = priv->plat->clk_csr;
+
 	return priv;
 
 error:

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

@@ -70,7 +70,7 @@ static int stmmac_mdio_read(struct mii_bus *bus, int phyaddr, int phyreg)
 	int data;
 	u16 regValue = (((phyaddr << 11) & (0x0000F800)) |
 			((phyreg << 6) & (0x000007C0)));
-	regValue |= MII_BUSY | ((priv->plat->clk_csr & 0xF) << 2);
+	regValue |= MII_BUSY | ((priv->clk_csr & 0xF) << 2);
 
 	if (stmmac_mdio_busy_wait(priv->ioaddr, mii_address))
 		return -EBUSY;
@@ -106,7 +106,7 @@ static int stmmac_mdio_write(struct mii_bus *bus, int phyaddr, int phyreg,
 	    (((phyaddr << 11) & (0x0000F800)) | ((phyreg << 6) & (0x000007C0)))
 	    | MII_WRITE;
 
-	value |= MII_BUSY | ((priv->plat->clk_csr & 0xF) << 2);
+	value |= MII_BUSY | ((priv->clk_csr & 0xF) << 2);
 
 	/* Wait until any existing MII operation is complete */
 	if (stmmac_mdio_busy_wait(priv->ioaddr, mii_address))