linux-kernel - Re: [PATCH v3 3/3] net/phy: micrel: Center FLP timing at 16ms

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Date:	Fri, 05 Jun 2015 15:43:38 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Jaeden Amero <jaeden.amero@...com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] net/phy: micrel: Center FLP timing at 16ms

On 05/06/15 15:40, Jaeden Amero wrote:
> Link failures have been observed when using the KSZ9031 with HP 1810-8G
> and HP 1910-8G network switches. Center the FLP timing at 16ms to help
> avoid intermittent link failures.
> 
> From the KSZ9031RNX and KSZ9031MNX data sheets revision 2.2, section
> "Auto-Negotiation Timing":
> 	The KSZ9031[RNX or MNX] Fast Link Pulse (FLP) burst-to-burst
> 	transmit timing for Auto-Negotiation defaults to 8ms. IEEE 802.3
> 	Standard specifies this timing to be 16ms +/-8ms. Some PHY link
> 	partners need to receive the FLP with 16ms centered timing;
> 	otherwise, there can be intermittent link failures and long
> 	link-up times.
> 
> 	After KSZ9031[RNX or MNX] power-up/reset, program the following
> 	register sequence to set the FLP timing to 16ms
> 
> 	Write Register Dh = 0x0000 // Set up register address for MMD – Device Address 0h
> 	Write Register Eh = 0x0004 // Select Register 4h of MMD – Device Address 0h
> 	Write Register Dh = 0x4000 // Select register data for MMD – Device Address 0h, Register 4h
> 	Write Register Eh = 0x0006 // Write value 0x0006 to MMD – Device Address 0h, Register 4h
> 	Write Register Dh = 0x0000 // Set up register address for MMD – Device Address 0h
> 	Write Register Eh = 0x0003 // Select Register 3h of MMD – Device Address 0h
> 	Write Register Dh = 0x4000 // Select register data for MMD – Device Address 0h, Register 3h
> 	Write Register Eh = 0x1A80 // Write value 0x1A80 to MMD – Device Address 0h, Register 3h
> 	Write Register 0h, Bit [9] = 1 // Restart Auto-Negotiation

Quoting a portion of the data-sheet on how to do this programming is
very strange considering that the code is going to be the reference, not
the commit message.

Other than that, this looks reasonable.

> 
> Signed-off-by: Jaeden Amero <jaeden.amero@...com>
> ---
>  drivers/net/phy/micrel.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
> index f23765e..499185e 100644
> --- a/drivers/net/phy/micrel.c
> +++ b/drivers/net/phy/micrel.c
> @@ -366,6 +366,10 @@ static int ksz9021_config_init(struct phy_device *phydev)
>  #define KSZ9031_PS_TO_REG		60
>  
>  /* Extended registers */
> +/* MMD Address 0x0 */
> +#define MII_KSZ9031RN_FLP_BURST_TX_LO	3
> +#define MII_KSZ9031RN_FLP_BURST_TX_HI	4
> +
>  /* MMD Address 0x2 */
>  #define MII_KSZ9031RN_CONTROL_PAD_SKEW	4
>  #define MII_KSZ9031RN_RX_DATA_PAD_SKEW	5
> @@ -427,6 +431,22 @@ static int ksz9031_of_load_skew_values(struct phy_device *phydev,
>  	return ksz9031_extended_write(phydev, OP_DATA, 2, reg, newval);
>  }
>  
> +static int ksz9031_center_flp_timing(struct phy_device *phydev)
> +{
> +	int result;
> +
> +	/* Center KSZ9031RNX FLP timing at 16ms. */
> +	result = ksz9031_extended_write(phydev, OP_DATA, 0,
> +					MII_KSZ9031RN_FLP_BURST_TX_HI, 0x0006);
> +	result = ksz9031_extended_write(phydev, OP_DATA, 0,
> +					MII_KSZ9031RN_FLP_BURST_TX_LO, 0x1A80);
> +
> +	if (result)
> +		return result;
> +
> +	return genphy_restart_aneg(phydev);
> +}
> +
>  static int ksz9031_config_init(struct phy_device *phydev)
>  {
>  	const struct device *dev = &phydev->dev;
> @@ -462,7 +482,8 @@ static int ksz9031_config_init(struct phy_device *phydev)
>  				MII_KSZ9031RN_TX_DATA_PAD_SKEW, 4,
>  				tx_data_skews, 4);
>  	}
> -	return 0;
> +
> +	return ksz9031_center_flp_timing(phydev);
>  }
>  
>  #define KSZ8873MLL_GLOBAL_CONTROL_4	0x06
> 


-- 
Florian
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