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

Nicolas Ferre
2013-10-15T07:54:25Z

On 15/10/2013 01:59, Soren Brinkmann :
> Adjust the ethernet clock according to the negotiated link speed.
>
> Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>

I will need more time to study this one.

Moreover, I will have to add the "tx_clk" to every user of this driver
before switchin to the addition of this clock.

Best regards,

> ---
> 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;
>

--
Nicolas Ferre