Subject: Re: [PATCH] net: mvneta: properly disable HW PHY polling and ensure adjust_link() works

From: Gregory CLEMENT <[email-masked]>
Date: Wed, 04 Sep 2013 18:08:59 +0200

On 04/09/2013 16:21, Thomas Petazzoni wrote:
> This commit fixes a long-standing bug that has been reported by many
> users: on some Armada 370 platforms, only the network interface that
> has been used in U-Boot to tftp the kernel works properly in
> Linux. The other network interfaces can see a 'link up', but are
> unable to transmit data. The reports were generally made on the Armada
> 370-based Mirabox, but have also been given on the Armada 370-RD
> board.
> 
> The network MAC in the Armada 370/XP (supported by the mvneta driver
> in Linux) has a functionality that allows it to continuously poll the
> PHY and directly update the MAC configuration accordingly (speed,
> duplex, etc.). The very first versions of the driver submitted for
> review were using this hardware mechanism, but due to this, the driver
> was not integrated with the kernel phylib. Following reviews, the
> driver was changed to use the phylib, and therefore a software based
> polling. In software based polling, Linux regularly talks to the PHY
> over the MDIO bus, and sees if the link status has changed. If it's
> the case then the adjust_link() callback of the driver is called to
> update the MAC configuration accordingly.
> 
> However, it turns out that the adjust_link() callback was not
> configuring the hardware in a completely correct way: while it was
> setting the speed and duplex bits correctly, it wasn't telling the
> hardware to actually take into account those bits rather than what the
> hardware-based PHY polling mechanism has concluded. So, in fact the
> adjust_link() callback was basically a no-op.
> 
> However, the network happened to be working because on the network
> interfaces used by U-Boot for tftp on Armada 370 platforms because the
> hardware PHY polling was enabled by the bootloader, and left enabled
> by Linux. However, the second network interface not used for tftp (or
> both network interfaces if the kernel is loaded from USB, NAND or SD
> card) didn't had the hardware PHY polling enabled.
> 
> This patch fixes this situation by:
> 
>  (1) Making sure that the hardware PHY polling is disabled by clearing
>      the MVNETA_PHY_POLLING_ENABLE bit in the MVNETA_UNIT_CONTROL
>      register in the driver ->probe() function.
> 
>  (2) Making sure that the duplex and speed selections made by the
>      adjust_link() callback are taken into account by clearing the
>      MVNETA_GMAC_AN_SPEED_EN and MVNETA_GMAC_AN_DUPLEX_EN bits in the
>      MVNETA_GMAC_AUTONEG_CONFIG register.
> 
> This patch has been tested on Armada 370 Mirabox, and now both network
> interfaces are usable after boot.
> 

Well done Thomas!

I have successfully tested it on Armada 370 Mirabox:

Tested-by: Gregory CLEMENT <[email-masked]>

Thanks

> Signed-off-by: Thomas Petazzoni <[email-masked]>
> Cc: Willy Tarreau <[email-masked]>
> Cc: Jochen De Smet <[email-masked]>
> Cc: Peter Sanford <[email-masked]>
> Cc: Ethan Tuttle <[email-masked]>
> Cc: Chény Yves-Gael <[email-masked]>
> Cc: Ryan Press <[email-masked]>
> Cc: Simon Guinot <[email-masked]>
> Cc: [email-masked]
> Cc: [email-masked]
> ---
> David, this patch is a fix for a problem that has been here since 3.8
> (when the mvneta driver was introduced), so I've Cc'ed stable@ and if
> possible I'd like to patch to be included for 3.12.
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index b017818..90ab292 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -138,7 +138,9 @@
>  #define      MVNETA_GMAC_FORCE_LINK_PASS         BIT(1)
>  #define      MVNETA_GMAC_CONFIG_MII_SPEED        BIT(5)
>  #define      MVNETA_GMAC_CONFIG_GMII_SPEED       BIT(6)
> +#define      MVNETA_GMAC_AN_SPEED_EN             BIT(7)
>  #define      MVNETA_GMAC_CONFIG_FULL_DUPLEX      BIT(12)
> +#define      MVNETA_GMAC_AN_DUPLEX_EN            BIT(13)
>  #define MVNETA_MIB_COUNTERS_BASE                 0x3080
>  #define      MVNETA_MIB_LATE_COLLISION           0x7c
>  #define MVNETA_DA_FILT_SPEC_MCAST                0x3400
> @@ -915,6 +917,13 @@ static void mvneta_defaults_set(struct mvneta_port *pp)
>  	/* Assign port SDMA configuration */
>  	mvreg_write(pp, MVNETA_SDMA_CONFIG, val);
>  
> +	/* Disable PHY polling in hardware, since we're using the
> +	 * kernel phylib to do this.
> +	 */
> +	val = mvreg_read(pp, MVNETA_UNIT_CONTROL);
> +	val &= ~MVNETA_PHY_POLLING_ENABLE;
> +	mvreg_write(pp, MVNETA_UNIT_CONTROL, val);
> +
>  	mvneta_set_ucast_table(pp, -1);
>  	mvneta_set_special_mcast_table(pp, -1);
>  	mvneta_set_other_mcast_table(pp, -1);
> @@ -2307,7 +2316,9 @@ static void mvneta_adjust_link(struct net_device *ndev)
>  			val = mvreg_read(pp, MVNETA_GMAC_AUTONEG_CONFIG);
>  			val &= ~(MVNETA_GMAC_CONFIG_MII_SPEED |
>  				 MVNETA_GMAC_CONFIG_GMII_SPEED |
> -				 MVNETA_GMAC_CONFIG_FULL_DUPLEX);
> +				 MVNETA_GMAC_CONFIG_FULL_DUPLEX |
> +				 MVNETA_GMAC_AN_SPEED_EN |
> +				 MVNETA_GMAC_AN_DUPLEX_EN);
>  
>  			if (phydev->duplex)
>  				val |= MVNETA_GMAC_CONFIG_FULL_DUPLEX;
> 

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com