netdev - Re: [PATCH v2 2/2] net: phy: motorcomm: Add pad drive strength cfg support

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Message-ID: <cda098be-eb4a-75dc-ea12-977766e9e843@starfivetech.com>
Date: Sat, 6 May 2023 09:52:52 +0800
From: Guo Samin <samin.guo@...rfivetech.com>
To: Frank Sae <Frank.Sae@...or-comm.com>, <linux-kernel@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <netdev@...r.kernel.org>, Peter Geis
	<pgwipeout@...il.com>
CC: "David S . Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Rob Herring <robh+dt@...nel.org>, Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@...aro.org>, Andrew Lunn <andrew@...n.ch>, "Heiner
 Kallweit" <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>,
	Yanhong Wang <yanhong.wang@...rfivetech.com>
Subject: Re: [PATCH v2 2/2] net: phy: motorcomm: Add pad drive strength cfg
 support

data: Re: [PATCH v2 2/2] net: phy: motorcomm: Add pad drive strength cfg support
From: Frank Sae <Frank.Sae@...or-comm.com>
to: Samin Guo <samin.guo@...rfivetech.com>, <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>, <netdev@...r.kernel.org>, Peter Geis <pgwipeout@...il.com>
data: 2023/5/6

> 
> 
> On 2023/5/5 17:05, Samin Guo wrote:
>> The motorcomm phy (YT8531) supports the ability to adjust the drive
>> strength of the rx_clk/rx_data, and the default strength may not be
>> suitable for all boards. So add configurable options to better match
>> the boards.(e.g. StarFive VisionFive 2)
>>
>> Signed-off-by: Samin Guo <samin.guo@...rfivetech.com>
>> ---
>>  drivers/net/phy/motorcomm.c | 46 +++++++++++++++++++++++++++++++++++++
>>  1 file changed, 46 insertions(+)
>>
>> diff --git a/drivers/net/phy/motorcomm.c b/drivers/net/phy/motorcomm.c
>> index 2fa5a90e073b..191650bb1454 100644
>> --- a/drivers/net/phy/motorcomm.c
>> +++ b/drivers/net/phy/motorcomm.c
>> @@ -236,6 +236,7 @@
>>   */
>>  #define YTPHY_WCR_TYPE_PULSE			BIT(0)
>>  
>> +#define YTPHY_PAD_DRIVE_STRENGTH_REG		0xA010
>>  #define YTPHY_SYNCE_CFG_REG			0xA012
>>  #define YT8521_SCR_SYNCE_ENABLE			BIT(5)
>>  /* 1b0 output 25m clock
>> @@ -260,6 +261,14 @@
>>  #define YT8531_SCR_CLK_SRC_REF_25M		4
>>  #define YT8531_SCR_CLK_SRC_SSC_25M		5
>>  
>> +#define YT8531_RGMII_RXC_DS_DEFAULT		0x3
>> +#define YT8531_RGMII_RXC_DS_MAX			0x7
>> +#define YT8531_RGMII_RXC_DS			GENMASK(15, 13)
>> +#define YT8531_RGMII_RXD_DS_DEFAULT		0x3
>> +#define YT8531_RGMII_RXD_DS_MAX			0x7
>> +#define YT8531_RGMII_RXD_DS_LOW			GENMASK(5, 4) /* Bit 1/0 of rxd_ds */
>> +#define YT8531_RGMII_RXD_DS_HI			BIT(12) /* Bit 2 of rxd_ds */
> 
> 
> YT8531_RGMII_xxx is bit define for YTPHY_PAD_DRIVE_STRENGTH_REG, so it is better to put it under the define of YTPHY_PAD_DRIVE_STRENGTH_REG.
> 
> YT8531_RGMII_xxx bit define as reverse order:
> #define YTPHY_PAD_DRIVE_STRENGTH_REG		0xA010
> #define YT8531_RGMII_RXC_DS			GENMASK(15, 13)
> #define YT8531_RGMII_RXD_DS_HI			BIT(12) /* Bit 2 of rxd_ds */     <-------
> #define YT8531_RGMII_RXD_DS_LOW			GENMASK(5, 4) /* Bit 1/0 of rxd_ds */
> ...
> 
Hi Frank,

Ok, will fix it next version.
btw, do you have any information you can provide about Andrew's mention of using real unit uA/mA  instead of magic numbers?
(I couldn't find any information about current in the YT8531's datasheet other than the magic numbers.)


Below is all the relevant information I found：

Pad Drive Strength Cfg (EXT_0xA010)

Bit   |  Symbol           |  Access |  Default |  Description
15:13 |  Rgmii_sw_dr_rx   |  RW     |  0x3     |  Drive strenght of rx_clk pad.
                                               |  3'b111: strongest; 3'b000: weakest.

12    |  Rgmii_sw_dr[2]   |  RW     |  0x0     |  Bit 2 of Rgmii_sw_dr[2:0], refer to ext A010[5:4]

5:4   |  Rgmii_sw_dr[1:0] |  RW     |  0x3     |  Bit 1 and 0 of Rgmii_sw_dr, Drive strenght of rxd/rx_ctl rgmii pad.
                                               |  3'b111: strongest; 3'b000: weakest


Best regards,
Samin

>> +
>>  /* Extended Register  end */
>>  
>>  #define YTPHY_DTS_OUTPUT_CLK_DIS		0
>> @@ -1495,6 +1504,7 @@ static int yt8531_config_init(struct phy_device *phydev)
>>  {
>>  	struct device_node *node = phydev->mdio.dev.of_node;
>>  	int ret;
>> +	u32 ds, val;
>>  
>>  	ret = ytphy_rgmii_clk_delay_config_with_lock(phydev);
>>  	if (ret < 0)
>> @@ -1518,6 +1528,42 @@ static int yt8531_config_init(struct phy_device *phydev)
>>  			return ret;
>>  	}
>>  
>> +	ds = YT8531_RGMII_RXC_DS_DEFAULT;
>> +	if (!of_property_read_u32(node, "motorcomm,rx-clk-driver-strength", &val)) {
>> +		if (val > YT8531_RGMII_RXC_DS_MAX)
>> +			return -EINVAL;
>> +
>> +		ds = val;
>> +	}
>> +
>> +	ret = ytphy_modify_ext_with_lock(phydev,
>> +					 YTPHY_PAD_DRIVE_STRENGTH_REG,
>> +					 YT8531_RGMII_RXC_DS,
>> +					 FIELD_PREP(YT8531_RGMII_RXC_DS, ds));
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	ds = FIELD_PREP(YT8531_RGMII_RXD_DS_LOW, YT8531_RGMII_RXD_DS_DEFAULT);
>> +	if (!of_property_read_u32(node, "motorcomm,rx-data-driver-strength", &val)) {
>> +		if (val > YT8531_RGMII_RXD_DS_MAX)
>> +			return -EINVAL;
>> +
>> +		if (val > FIELD_MAX(YT8531_RGMII_RXD_DS_LOW)) {
>> +			ds = val & FIELD_MAX(YT8531_RGMII_RXD_DS_LOW);
>> +			ds = FIELD_PREP(YT8531_RGMII_RXD_DS_LOW, ds);
>> +			ds |= YT8531_RGMII_RXD_DS_HI;
>> +		} else {
>> +			ds = FIELD_PREP(YT8531_RGMII_RXD_DS_LOW, val);
>> +		}
>> +	}
>> +
>> +	ret = ytphy_modify_ext_with_lock(phydev,
>> +					 YTPHY_PAD_DRIVE_STRENGTH_REG,
>> +					 YT8531_RGMII_RXD_DS_LOW | YT8531_RGMII_RXD_DS_HI,
>> +					 ds);
>> +	if (ret < 0)
>> +		return ret;
>> +
>>  	return 0;
>>  }
>>