[PATCH RFC 5/5] net: macb: Adjust tx_clk when link speed changes

Soren Brinkmann
2013-10-14T23:59:44Z

Adjust the ethernet clock according to the negotiated link speed.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
---
drivers/net/ethernet/cadence/macb.c | 66 +++++++++++++++++++++++++++++++++++++
drivers/net/ethernet/cadence/macb.h | 1 +
2 files changed, 67 insertions(+)

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 603844b1d483..beb9fa863811 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -204,6 +204,49 @@ static int macb_mdio_reset(struct mii_bus *bus)
return 0;
}

+/**
+ * macb_set_tx_clk() - Set a clock to a new frequency
+ * @clk Pointer to the clock to change
+ * @rate New frequency in Hz
+ * @dev Pointer to the struct net_device
+ */
+static void macb_set_tx_clk(struct clk *clk, int speed, struct net_device *dev)
+{
+ long ferr;
+ long rate;
+ long rate_rounded;
+
+ switch (speed) {
+ case SPEED_10:
+ rate = 2500000;
+ break;
+ case SPEED_100:
+ rate = 25000000;
+ break;
+ case SPEED_1000:
+ rate = 125000000;
+ break;
+ default:
+ break;
+ }
+
+ rate_rounded = clk_round_rate(clk, rate);
+ if (rate_rounded < 0)
+ return;
+
+ /* RGMII allows 50 ppm frequency error. Test and warn if this limit
+ * are not satisfied.
+ */
+ ferr = abs(rate_rounded - rate);
+ ferr = DIV_ROUND_UP(ferr, rate / 100000);
+ if (ferr > 5)
+ netdev_warn(dev, "unable to generate target frequency: %ld Hz\n",
+ rate);
+
+ if (clk_set_rate(clk, rate_rounded))
+ netdev_err(dev, "adjusting tx_clk failed.\n");
+}
+
static void macb_handle_link_change(struct net_device *dev)
{
struct macb *bp = netdev_priv(dev);
@@ -251,6 +294,9 @@ static void macb_handle_link_change(struct net_device *dev)

spin_unlock_irqrestore(&bp->lock, flags);

+ if (!IS_ERR(bp->tx_clk))
+ macb_set_tx_clk(bp->tx_clk, phydev->speed, dev);
+
if (status_change) {
if (phydev->link) {
netif_carrier_on(dev);
@@ -1805,6 +1851,8 @@ static int __init macb_probe(struct platform_device *pdev)
goto err_out_free_dev;
}

+ bp->tx_clk = devm_clk_get(&pdev->dev, "tx_clk");
+
err = clk_prepare_enable(bp->pclk);
if (err) {
dev_err(&pdev->dev, "failed to enable pclk (%u)\n", err);
@@ -1817,6 +1865,15 @@ static int __init macb_probe(struct platform_device *pdev)
goto err_out_disable_pclk;
}

+ if (!IS_ERR(bp->tx_clk)) {
+ err = clk_prepare_enable(bp->tx_clk);
+ if (err) {
+ dev_err(&pdev->dev, "failed to enable tx_clk (%u)\n",
+ err);
+ goto err_out_disable_hclk;
+ }
+ }
+
bp->regs = devm_ioremap(&pdev->dev, regs->start, resource_size(regs));
if (!bp->regs) {
dev_err(&pdev->dev, "failed to map registers, aborting.\n");
@@ -1917,6 +1974,9 @@ static int __init macb_probe(struct platform_device *pdev)
err_out_unregister_netdev:
unregister_netdev(dev);
err_out_disable_clocks:
+ if (!IS_ERR(bp->tx_clk))
+ clk_disable_unprepare(bp->tx_clk);
+err_out_disable_hclk:
clk_disable_unprepare(bp->hclk);
err_out_disable_pclk:
clk_disable_unprepare(bp->pclk);
@@ -1941,6 +2001,8 @@ static int __exit macb_remove(struct platform_device *pdev)
kfree(bp->mii_bus->irq);
mdiobus_free(bp->mii_bus);
unregister_netdev(dev);
+ if (!IS_ERR(bp->tx_clk))
+ clk_disable_unprepare(bp->tx_clk);
clk_disable_unprepare(bp->hclk);
clk_disable_unprepare(bp->pclk);
free_netdev(dev);
@@ -1959,6 +2021,8 @@ static int macb_suspend(struct device *dev)
netif_carrier_off(netdev);
netif_device_detach(netdev);

+ if (!IS_ERR(bp->tx_clk))
+ clk_disable_unprepare(bp->tx_clk);
clk_disable_unprepare(bp->hclk);
clk_disable_unprepare(bp->pclk);

@@ -1973,6 +2037,8 @@ static int macb_resume(struct device *dev)

clk_prepare_enable(bp->pclk);
clk_prepare_enable(bp->hclk);
+ if (!IS_ERR(bp->tx_clk))
+ clk_prepare_enable(bp->tx_clk);

netif_device_attach(netdev);

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index f4076155bed7..51c02442160a 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -572,6 +572,7 @@ struct macb {
struct platform_device *pdev;
struct clk *pclk;
struct clk *hclk;
+ struct clk *tx_clk;
struct net_device *dev;
struct napi_struct napi;
struct work_struct tx_error_task;
--
1.8.4