[PATCH RFC net-next 1/7] net: stmmac: provide generic transmit clock configuration hook

["Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>]

Several stmmac sub-drivers which support RGMII follow the same pattern.
They calculate the transmit clock, and then call the clk API to set a
clock to that rate.

Analysis of documentation suggests that the platform is responsible for
providing the transmit clock to the DWMAC core (clk_tx_i). The expected
rates are:

	10Mbps	100Mbps	1Gbps
MII	2.5MHz	25MHz
GMII			125MHz
RGMI	2.5MHz	25MHz	125MHz
RMII	2.5MHz	25MHz

It seems some platforms require this clock to be manually configured,
but there are outputs from the MAC core that indicate the speed, so a
platform may use these to automatically configure the clock. Thus, we
can't just provide one solution to configuring the clock.

Moreover, the clock may need to be derived from one of several sources
depending on the interface mode.

Provide a platform hook that is passed the interface mode, speed, and
transmit clock.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 11 +++++++++++
 include/linux/stmmac.h                            |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 4d542f482ecb..f7ff94a09da2 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -928,6 +928,7 @@ static void stmmac_mac_link_up(struct phylink_config *config,
 	struct stmmac_priv *priv = netdev_priv(to_net_dev(config->dev));
 	unsigned int flow_ctrl;
 	u32 old_ctrl, ctrl;
+	int ret;
 
 	if ((priv->plat->flags & STMMAC_FLAG_SERDES_UP_AFTER_PHY_LINKUP) &&
 	    priv->plat->serdes_powerup)
@@ -1000,6 +1001,16 @@ static void stmmac_mac_link_up(struct phylink_config *config,
 	if (priv->plat->fix_mac_speed)
 		priv->plat->fix_mac_speed(priv->plat->bsp_priv, speed, mode);
 
+	if (priv->plat->set_clk_tx_rate) {
+		ret = priv->plat->set_clk_tx_rate(priv->plat->bsp_priv,
+						priv->plat->clk_tx_i,
+						interface, speed);
+		if (ret < 0)
+			netdev_err(priv->dev,
+				   "failed to configure transmit clock for %dMbps: %pe\n",
+				   speed, ERR_PTR(ret));
+	}
+
 	if (!duplex)
 		ctrl &= ~priv->hw->link.duplex;
 	else
diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
index 6d2aa77ea963..cd0d1383df87 100644
--- a/include/linux/stmmac.h
+++ b/include/linux/stmmac.h
@@ -78,6 +78,7 @@
 			| DMA_AXI_BLEN_32 | DMA_AXI_BLEN_64 \
 			| DMA_AXI_BLEN_128 | DMA_AXI_BLEN_256)
 
+struct clk;
 struct stmmac_priv;
 
 /* Platfrom data for platform device structure's platform_data field */
@@ -231,6 +232,8 @@ struct plat_stmmacenet_data {
 	u8 tx_sched_algorithm;
 	struct stmmac_rxq_cfg rx_queues_cfg[MTL_MAX_RX_QUEUES];
 	struct stmmac_txq_cfg tx_queues_cfg[MTL_MAX_TX_QUEUES];
+	int (*set_clk_tx_rate)(void *priv, struct clk *clk_tx_i,
+			       phy_interface_t interface, int speed);
 	void (*fix_mac_speed)(void *priv, int speed, unsigned int mode);
 	int (*fix_soc_reset)(void *priv, void __iomem *ioaddr);
 	int (*serdes_powerup)(struct net_device *ndev, void *priv);
@@ -252,6 +255,7 @@ struct plat_stmmacenet_data {
 	struct clk *stmmac_clk;
 	struct clk *pclk;
 	struct clk *clk_ptp_ref;
+	struct clk *clk_tx_i;		/* clk_tx_i to MAC core */
 	unsigned long clk_ptp_rate;
 	unsigned long clk_ref_rate;
 	struct clk_bulk_data *clks;
-- 
2.30.2