Subject: Re: [PATCH net-next v9 1/1] net: phy: Cleanup the Edge-Rate feature in Microsemi PHYs.

From: Andrew Lunn <[email-masked]>
Date: Fri, 7 Oct 2016 22:22:25 +0200

On Fri, Oct 07, 2016 at 10:28:24AM +0200, Allan W. Nielsen wrote:
> Edge-Rate cleanup include the following:
> - Updated device tree bindings documentation for edge-rate
> - The edge-rate is now specified as a "slowdown", meaning that it is now
>   being specified as positive values instead of negative (both
>   documentation and implementation wise).
> - Only explicitly documented values for "vsc8531,vddmac" and
>   "vsc8531,edge-slowdown" are accepted by the device driver.
> - Deleting include/dt-bindings/net/mscc-phy-vsc8531.h as it was not needed.
> 
> Signed-off-by: Allan W. Nielsen <[email-masked]>
> Signed-off-by: Raju Lakkaraju <[email-masked]>
> ---
>  .../devicetree/bindings/net/mscc-phy-vsc8531.txt   | 49 ++++++++------
>  drivers/net/phy/mscc.c                             | 79 +++++++++++++---------
>  include/dt-bindings/net/mscc-phy-vsc8531.h         | 21 ------
>  3 files changed, 75 insertions(+), 74 deletions(-)
>  delete mode 100644 include/dt-bindings/net/mscc-phy-vsc8531.h
> 
> diff --git a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> index 99c7eb0..f552033 100644
> --- a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> +++ b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> @@ -6,20 +6,27 @@ Required properties:
>  		  Documentation/devicetree/bindings/net/phy.txt
>  
>  Optional properties:
> -- vsc8531,vddmac	: The vddmac in mV.
> +- vsc8531,vddmac	: The vddmac in mV. Allowed values is listed
> +			  in the first row of Table 1 (below).
> +			  This property is only used in combination
> +			  with the 'edge-slowdown' property.
> +			  Default value is 3300.
>  - vsc8531,edge-slowdown	: % the edge should be slowed down relative to
> -			  the fastest possible edge time. Native sign
> -			  need not enter.
> +			  the fastest possible edge time.
>  			  Edge rate sets the drive strength of the MAC
> -			  interface output signals.  Changing the drive
> -			  strength will affect the edge rate of the output
> -			  signal.  The goal of this setting is to help
> -			  reduce electrical emission (EMI) by being able
> -			  to reprogram drive strength and in effect slow
> -			  down the edge rate if desired.  Table 1 shows the
> -			  impact to the edge rate per VDDMAC supply for each
> -			  drive strength setting.
> -			  Ref: Table:1 - Edge rate change below.
> +			  interface output signals.  Changing the
> +			  drive strength will affect the edge rate of
> +			  the output signal.  The goal of this setting
> +			  is to help reduce electrical emission (EMI)
> +			  by being able to reprogram drive strength
> +			  and in effect slow down the edge rate if
> +			  desired.
> +			  To adjust the edge-slowdown, the 'vddmac'
> +			  must be specified. Table 1 lists the
> +			  supported edge-slowdown values for a given
> +			  'vddmac'.
> +			  Default value is 0%.
> +			  Ref: Table:1 - Edge rate change (below).
>  
>  Note: see dt-bindings/net/mscc-phy-vsc8531.h for applicable values

Hi Allen

Overall, this is much better. I just have a few nitpicks.

dt-bindings/net/mscc-phy-vsc8531.h is removed by this patch. It would
be good to also remove the reference.

>  
> @@ -29,23 +36,23 @@ Table: 1 - Edge rate change
>  |								|
>  | 3300 mV	2500 mV		1800 mV		1500 mV		|
>  |---------------------------------------------------------------|
> -| Default	Deafult		Default		Default		|
> +| 0%		0%		0%		0%		|
>  | (Fastest)			(recommended)	(recommended)	|
>  |---------------------------------------------------------------|
> -| -2%		-3%		-5%		-6%		|
> +| 2%		3%		5%		6%		|
>  |---------------------------------------------------------------|
> -| -4%		-6%		-9%		-14%		|
> +| 4%		6%		9%		14%		|
>  |---------------------------------------------------------------|
> -| -7%		-10%		-16%		-21%		|
> +| 7%		10%		16%		21%		|
>  |(recommended)	(recommended)					|
>  |---------------------------------------------------------------|
> -| -10%		-14%		-23%		-29%		|
> +| 10%		14%		23%		29%		|
>  |---------------------------------------------------------------|
> -| -17%		-23%		-35%		-42%		|
> +| 17%		23%		35%		42%		|
>  |---------------------------------------------------------------|
> -| -29%		-37%		-52%		-58%		|
> +| 29%		37%		52%		58%		|
>  |---------------------------------------------------------------|
> -| -53%		-63%		-76%		-77%		|
> +| 53%		63%		76%		77%		|
>  | (slowest)							|
>  |---------------------------------------------------------------|
>  
> @@ -54,5 +61,5 @@ Example:
>          vsc8531_0: ethernet-phy@0 {
>                  compatible = "ethernet-phy-id0007.0570";
>                  vsc8531,vddmac		= <3300>;
> -                vsc8531,edge-slowdown	= <21>;
> +                vsc8531,edge-slowdown	= <7>;
>          };
> diff --git a/drivers/net/phy/mscc.c b/drivers/net/phy/mscc.c
> index a17573e..2bd00b6 100644
> --- a/drivers/net/phy/mscc.c
> +++ b/drivers/net/phy/mscc.c
> @@ -12,7 +12,6 @@
>  #include <linux/mii.h>
>  #include <linux/phy.h>
>  #include <linux/of.h>
> -#include <dt-bindings/net/mscc-phy-vsc8531.h>
>  
>  enum rgmii_rx_clock_delay {
>  	RGMII_RX_CLK_DELAY_0_2_NS = 0,
> @@ -56,21 +55,27 @@ enum rgmii_rx_clock_delay {
>  #define PHY_ID_VSC8531			  0x00070570
>  #define PHY_ID_VSC8541			  0x00070770
>  
> -struct edge_rate_table {
> +#define MSCC_VDDMAC_1500		  1500
> +#define MSCC_VDDMAC_1800		  1800
> +#define MSCC_VDDMAC_2500		  2500
> +#define MSCC_VDDMAC_3300		  3300
> +
> +struct vsc8531_edge_rate_table {
>  	u16 vddmac;
> -	int slowdown[MSCC_SLOWDOWN_MAX];
> +	u8 slowdown[8];
>  };
>  
> -struct edge_rate_table edge_table[MSCC_VDDMAC_MAX] = {
> -	{3300, { 0, -2, -4,  -7,  -10, -17, -29, -53} },
> -	{2500, { 0, -3, -6,  -10, -14, -23, -37, -63} },
> -	{1800, { 0, -5, -9,  -16, -23, -35, -52, -76} },
> -	{1500, { 0, -6, -14, -21, -29, -42, -58, -77} },
> +static const struct vsc8531_edge_rate_table edge_table[] = {
> +	{MSCC_VDDMAC_3300, { 0, 2,  4,  7, 10, 17, 29, 53} },
> +	{MSCC_VDDMAC_2500, { 0, 3,  6, 10, 14, 23, 37, 63} },
> +	{MSCC_VDDMAC_1800, { 0, 5,  9, 16, 23, 35, 52, 76} },
> +	{MSCC_VDDMAC_1500, { 0, 6, 14, 21, 29, 42, 58, 77} },
>  };
>  
>  struct vsc8531_private {
>  	u8 edge_slowdown;
>  	u16 vddmac;
> +	int rate_magic;
>  };

You don't need edge_slowdown and vddmac in the private structure,
since they are never used after determining what rate_magic is.

>  
>  static int vsc85xx_phy_page_set(struct phy_device *phydev, u8 page)
> @@ -81,29 +86,21 @@ static int vsc85xx_phy_page_set(struct phy_device *phydev, u8 page)
>  	return rc;
>  }
>  
> -static u8 edge_rate_magic_get(u16 vddmac,
> -			      int slowdown)
> +static int vsc85xx_edge_rate_magic_get(u16 vddmac, u8 slowdown)
>  {
> -	int rc = (MSCC_SLOWDOWN_MAX - 1);
>  	u8 vdd;
>  	u8 sd;
> -
> -	for (vdd = 0; vdd < MSCC_VDDMAC_MAX; vdd++) {
> -		if (edge_table[vdd].vddmac == vddmac) {
> -			for (sd = 0; sd < MSCC_SLOWDOWN_MAX; sd++) {
> -				if (edge_table[vdd].slowdown[sd] <= slowdown) {
> -					rc = (MSCC_SLOWDOWN_MAX - sd - 1);
> -					break;
> -				}
> -			}
> -		}
> -	}
> -
> -	return rc;
> +	u8 sd_array_size = ARRAY_SIZE(edge_table[0].slowdown);
> +
> +	for (vdd = 0; vdd < ARRAY_SIZE(edge_table); vdd++)
> +		if (edge_table[vdd].vddmac == vddmac)
> +			for (sd = 0; sd < sd_array_size; sd++)
> +				if (edge_table[vdd].slowdown[sd] == slowdown)
> +					return (sd_array_size - sd - 1);
> +	return -EINVAL;
>  }
>  
> -static int vsc85xx_edge_rate_cntl_set(struct phy_device *phydev,
> -				      u8 edge_rate)
> +static int vsc85xx_edge_rate_cntl_set(struct phy_device *phydev, u8 edge_rate)
>  {
>  	int rc;
>  	u16 reg_val;
> @@ -199,17 +196,38 @@ static int vsc8531_of_init(struct phy_device *phydev)
>  				  &vsc8531->vddmac);
>  	if (rc == -EINVAL)
>  		vsc8531->vddmac = MSCC_VDDMAC_3300;
> +
>  	rc = of_property_read_u8(of_node, "vsc8531,edge-slowdown",
>  				 &vsc8531->edge_slowdown);
>  	if (rc == -EINVAL)
>  		vsc8531->edge_slowdown = 0;
>  
> -	rc = 0;
> -	return rc;
> +	vsc8531->rate_magic = vsc85xx_edge_rate_magic_get(
> +		vsc8531->vddmac, vsc8531->edge_slowdown);
> +	if (vsc8531->rate_magic < 0) {
> +		phydev_err(phydev,
> +			   "Invalid vsc8531,vddmac or vsc8531,edge-slowdown");
> +		return vsc8531->rate_magic;
> +	}
> +
> +	return 0;
>  }
>  #else
>  static int vsc8531_of_init(struct phy_device *phydev)
>  {
> +	struct vsc8531_private *vsc8531 = phydev->priv;
> +
> +	vsc8531->vddmac = MSCC_VDDMAC_3300;
> +	vsc8531->edge_slowdown = 0;
> +
> +	vsc8531->rate_magic = vsc85xx_edge_rate_magic_get(
> +		vsc8531->vddmac, vsc8531->edge_slowdown);
> +	if (vsc8531->rate_magic < 0) {
> +		phydev_err(phydev,
> +			   "Invalid vsc8531,vddmac or vsc8531,edge-slowdown");
> +		return vsc8531->rate_magic;
> +	}

You could skip all this and just have:

    vsc8531->rate_magic = 0;

vsc8531->vddmac and vsc8531->edge_slowdown are not used anywhere else.

	Andrew