netdev - Re: [PATCH net] gianfar: Don't force RGMII mode after reset, use defaults

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Message-ID: <20191112164707.GQ18744@zorba>
Date:   Tue, 12 Nov 2019 08:47:07 -0800
From:   Daniel Walker <danielwa@...co.com>
To:     Claudiu Manoil <claudiu.manoil@....com>
Cc:     "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        sjarugum@...co.com, hramdasi@...co.com
Subject: Re: [PATCH net] gianfar: Don't force RGMII mode after reset, use
 defaults



Just adding HEMANT who was involved in the original debug.
Also Sathish did the current debug.


On Tue, Nov 12, 2019 at 04:55:11PM +0200, Claudiu Manoil wrote:
> We received reports that forcing the MAC into RGMII (1 Gbps)
> interface mode after MAC reset occasionally disrupts operation
> of PHYs capable only of 100Mbps, even after adjust_link kicks
> in and re-adjusts the interface mode in MACCFG2 accordingly.
> Instead of forcing MACCFG2 into RGMII mode, let's use the default
> reset value of MACCFG2 (that leaves the IF_Mode field unset) and
> let adjust_link configure the correct mode from the beginning.
> MACCFG2_INIT_SETTINGS is dropped, only the PAD_CRC bit is preserved,
> the remaining fields (IF_Mode and Duplex) are left for adjust_link.
> Tested on boards with gigabit PHYs.
> 
> MACCFG2_INIT_SETTINGS is there since day one, but the issue
> got visible after introducing the MAC reset and reconfig support,
> which added MAC reset at runtime, at interface open.
> 
> Fixes: a328ac92d314 ("gianfar: Implement MAC reset and reconfig procedure")
> 
> Reported-by: Daniel Walker <danielwa@...co.com>
> Signed-off-by: Claudiu Manoil <claudiu.manoil@....com>
> ---
>  drivers/net/ethernet/freescale/gianfar.c | 3 ++-
>  drivers/net/ethernet/freescale/gianfar.h | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
> index 51ad864..0f4d13d 100644
> --- a/drivers/net/ethernet/freescale/gianfar.c
> +++ b/drivers/net/ethernet/freescale/gianfar.c
> @@ -3173,7 +3173,8 @@ void gfar_mac_reset(struct gfar_private *priv)
>  	gfar_write(&regs->minflr, MINFLR_INIT_SETTINGS);
>  
>  	/* Initialize MACCFG2. */
> -	tempval = MACCFG2_INIT_SETTINGS;
> +	tempval = gfar_read(&regs->maccfg2);
> +	tempval |= MACCFG2_PAD_CRC;
>  
>  	/* eTSEC74 erratum: Rx frames of length MAXFRM or MAXFRM-1
>  	 * are marked as truncated.  Avoid this by MACCFG2[Huge Frame]=1,
> diff --git a/drivers/net/ethernet/freescale/gianfar.h b/drivers/net/ethernet/freescale/gianfar.h
> index f472a6d..cc70e03 100644
> --- a/drivers/net/ethernet/freescale/gianfar.h
> +++ b/drivers/net/ethernet/freescale/gianfar.h
> @@ -150,8 +150,8 @@ extern const char gfar_driver_version[];
>  #define MACCFG1_SYNCD_TX_EN	0x00000002
>  #define MACCFG1_TX_EN		0x00000001
>  
> -#define MACCFG2_INIT_SETTINGS	0x00007205
>  #define MACCFG2_FULL_DUPLEX	0x00000001
> +#define MACCFG2_PAD_CRC         0x00000004
>  #define MACCFG2_IF              0x00000300
>  #define MACCFG2_MII             0x00000100
>  #define MACCFG2_GMII            0x00000200
> -- 
> 2.7.4
>