net: xpcs: add function to configure EEE clock multiplying factor

Add a function to separate out the EEE clock multiplying factor. This
will be called by the stmmac driver to configure this value.

It would have been better had the driver used the CLK API to retrieve
this clock, get its rate and calculate the appropriate multiplier, but
that door has closed.

Signed-off-by: Russell King (Oracle) <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Russell King (Oracle)

drivers/net/pcs/pcs-xpcs.c

@@ -1193,6 +1193,20 @@ static void xpcs_an_restart(struct phylink_pcs *pcs)
 		    BMCR_ANRESTART);
 }
 
+/**
+ * xpcs_config_eee_mult_fact() - set the EEE clock multiplying factor
+ * @xpcs: pointer to a &struct dw_xpcs instance
+ * @mult_fact: the multiplying factor
+ *
+ * Configure the EEE clock multiplying factor. This value should be such that
+ * clk_eee_time_period * (mult_fact + 1) is within the range 80 to 120ns.
+ */
+void xpcs_config_eee_mult_fact(struct dw_xpcs *xpcs, u8 mult_fact)
+{
+	xpcs->eee_mult_fact = mult_fact;
+}
+EXPORT_SYMBOL_GPL(xpcs_config_eee_mult_fact);
+
 static int xpcs_read_ids(struct dw_xpcs *xpcs)
 {
 	int ret;

drivers/net/pcs/pcs-xpcs.h

@@ -122,6 +122,7 @@ struct dw_xpcs {
 	struct phylink_pcs pcs;
 	phy_interface_t interface;
 	bool need_reset;
+	u8 eee_mult_fact;
 };
 
 int xpcs_read(struct dw_xpcs *xpcs, int dev, u32 reg);

include/linux/pcs/pcs-xpcs.h

@@ -52,6 +52,7 @@ struct phylink_pcs *xpcs_to_phylink_pcs(struct dw_xpcs *xpcs);
 int xpcs_get_an_mode(struct dw_xpcs *xpcs, phy_interface_t interface);
 int xpcs_config_eee(struct dw_xpcs *xpcs, int mult_fact_100ns,
 		    int enable);
+void xpcs_config_eee_mult_fact(struct dw_xpcs *xpcs, u8 mult_fact);
 struct dw_xpcs *xpcs_create_mdiodev(struct mii_bus *bus, int addr);
 struct dw_xpcs *xpcs_create_fwnode(struct fwnode_handle *fwnode);
 void xpcs_destroy(struct dw_xpcs *xpcs);