linux-kernel - Re: [PATCH v5 3/3] net: phy: mscc: handle the clkout control on some phy variants

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Date:   Thu, 18 Jun 2020 15:28:22 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     davem@...emloft.net, kuba@...nel.org, robh+dt@...nel.org,
        f.fainelli@...il.com, hkallweit1@...il.com, linux@...linux.org.uk,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        christoph.muellner@...obroma-systems.com,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>
Subject: Re: [PATCH v5 3/3] net: phy: mscc: handle the clkout control on some
 phy variants

On Thu, Jun 18, 2020 at 02:11:39PM +0200, Heiko Stuebner wrote:
> From: Heiko Stuebner <heiko.stuebner@...obroma-systems.com>
> 
> At least VSC8530/8531/8540/8541 contain a clock output that can emit
> a predefined rate of 25, 50 or 125MHz.
> 
> This may then feed back into the network interface as source clock.
> So expose a clock-provider from the phy using the common clock framework
> to allow setting the rate.
> 
> Signed-off-by: Heiko Stuebner <heiko.stuebner@...obroma-systems.com>
> ---
>  drivers/net/phy/mscc/mscc.h      |  13 +++
>  drivers/net/phy/mscc/mscc_main.c | 182 +++++++++++++++++++++++++++++--
>  2 files changed, 187 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/phy/mscc/mscc.h b/drivers/net/phy/mscc/mscc.h
> index fbcee5fce7b2..94883dab5cc1 100644
> --- a/drivers/net/phy/mscc/mscc.h
> +++ b/drivers/net/phy/mscc/mscc.h
> @@ -218,6 +218,13 @@ enum rgmii_clock_delay {
>  #define INT_MEM_DATA_M			  0x00ff
>  #define INT_MEM_DATA(x)			  (INT_MEM_DATA_M & (x))
>  
> +#define MSCC_CLKOUT_CNTL		  13
> +#define CLKOUT_ENABLE			  BIT(15)
> +#define CLKOUT_FREQ_MASK		  GENMASK(14, 13)
> +#define CLKOUT_FREQ_25M			  (0x0 << 13)
> +#define CLKOUT_FREQ_50M			  (0x1 << 13)
> +#define CLKOUT_FREQ_125M		  (0x2 << 13)
> +
>  #define MSCC_PHY_PROC_CMD		  18
>  #define PROC_CMD_NCOMPLETED		  0x8000
>  #define PROC_CMD_FAILED			  0x4000
> @@ -360,6 +367,12 @@ struct vsc8531_private {
>  	 */
>  	unsigned int base_addr;
>  
> +#ifdef CONFIG_COMMON_CLK
> +	struct clk_hw clkout_hw;
> +#endif
> +	u32 clkout_rate;
> +	int clkout_enabled;
> +
>  #if IS_ENABLED(CONFIG_MACSEC)
>  	/* MACsec fields:
>  	 * - One SecY per device (enforced at the s/w implementation level)
> diff --git a/drivers/net/phy/mscc/mscc_main.c b/drivers/net/phy/mscc/mscc_main.c
> index 5d2777522fb4..727a9dd58403 100644
> --- a/drivers/net/phy/mscc/mscc_main.c
> +++ b/drivers/net/phy/mscc/mscc_main.c
> @@ -7,6 +7,7 @@
>   * Copyright (c) 2016 Microsemi Corporation
>   */
>  
> +#include <linux/clk-provider.h>
>  #include <linux/firmware.h>
>  #include <linux/jiffies.h>
>  #include <linux/kernel.h>
> @@ -431,7 +432,6 @@ static int vsc85xx_dt_led_mode_get(struct phy_device *phydev,
>  
>  	return led_mode;
>  }
> -
>  #else
>  static int vsc85xx_edge_rate_magic_get(struct phy_device *phydev)
>  {
> @@ -1508,6 +1508,43 @@ static int vsc85xx_config_init(struct phy_device *phydev)
>  	return 0;
>  }
>  
> +static int vsc8531_config_init(struct phy_device *phydev)
> +{
> +	struct vsc8531_private *vsc8531 = phydev->priv;
> +	u16 val;
> +	int rc;
> +
> +	rc = vsc85xx_config_init(phydev);
> +	if (rc)
> +		return rc;
> +
> +#ifdef CONFIG_COMMON_CLK
> +	switch (vsc8531->clkout_rate) {
> +	case 25000000:
> +		val = CLKOUT_FREQ_25M;
> +		break;
> +	case 50000000:
> +		val = CLKOUT_FREQ_50M;
> +		break;
> +	case 125000000:
> +		val = CLKOUT_FREQ_125M;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	if (vsc8531->clkout_enabled)
> +		val |= CLKOUT_ENABLE;
> +
> +	rc = phy_write_paged(phydev, MSCC_PHY_PAGE_EXTENDED_GPIO,
> +			     MSCC_CLKOUT_CNTL, val);
> +	if (rc)
> +		return rc;
> +#endif
> +
> +	return 0;
> +}
> +

> +static int vsc8531_clkout_prepare(struct clk_hw *hw)
> +{
> +	struct vsc8531_private *vsc8531 = clkout_hw_to_vsc8531(hw);
> +
> +	vsc8531->clkout_enabled = true;
> +	return 0;
> +}
> +
> +static void vsc8531_clkout_unprepare(struct clk_hw *hw)
> +{
> +	struct vsc8531_private *vsc8531 = clkout_hw_to_vsc8531(hw);
> +
> +	vsc8531->clkout_enabled = false;
> +}
> +

> +static const struct clk_ops vsc8531_clkout_ops = {
> +	.prepare = vsc8531_clkout_prepare,
> +	.unprepare = vsc8531_clkout_unprepare,
> +	.is_prepared = vsc8531_clkout_is_prepared,
> +	.recalc_rate = vsc8531_clkout_recalc_rate,
> +	.round_rate = vsc8531_clkout_round_rate,
> +	.set_rate = vsc8531_clkout_set_rate,

I'm not sure this is the expected behaviour. The clk itself should
only start ticking when the enable callback is called. But this code
will enable the clock when config_init() is called. I think you should
implement the enable and disable methods.

	  Andrew