netdev - Re: [PATCH net-next 2/3] net: phy: broadcom: Fix RXC/TXC auto disabling

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Message-ID: <20210213011147.6jedwieopekiwxqd@skbuf>
Date:   Sat, 13 Feb 2021 03:11:47 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Michael Chan <mchan@...adcom.com>,
        "open list:BROADCOM ETHERNET PHY DRIVERS" 
        <bcm-kernel-feedback-list@...adcom.com>,
        open list <linux-kernel@...r.kernel.org>, michael@...le.cc
Subject: Re: [PATCH net-next 2/3] net: phy: broadcom: Fix RXC/TXC auto
 disabling

On Fri, Feb 12, 2021 at 12:57:20PM -0800, Florian Fainelli wrote:
> When support for optionally disabling the TXC was introduced, bit 2 was
> used to do that operation but the datasheet for 50610M from 2009 does
> not show bit 2 as being defined. Bit 8 is the one that allows automatic
> disabling of the RXC/TXC auto disabling during auto power down.
> 
> Fixes: 52fae0837153 ("tg3 / broadcom: Optionally disable TXC if no link")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  include/linux/brcmphy.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/brcmphy.h b/include/linux/brcmphy.h
> index da7bf9dfef5b..3dd8203cf780 100644
> --- a/include/linux/brcmphy.h
> +++ b/include/linux/brcmphy.h
> @@ -193,7 +193,7 @@
>  #define BCM54XX_SHD_SCR3		0x05
>  #define  BCM54XX_SHD_SCR3_DEF_CLK125	0x0001
>  #define  BCM54XX_SHD_SCR3_DLLAPD_DIS	0x0002
> -#define  BCM54XX_SHD_SCR3_TRDDAPD	0x0004
> +#define  BCM54XX_SHD_SCR3_TRDDAPD	0x0100
>  
>  /* 01010: Auto Power-Down */
>  #define BCM54XX_SHD_APD			0x0a
> -- 
> 2.25.1
> 

We may have a problem here, with the layout of the Spare Control 3
register not being as universal as we think.

Your finding may have been the same as Kevin Lo's from commit
b0ed0bbfb304 ("net: phy: broadcom: add support for BCM54811 PHY"),
therefore your change is making BCM54XX_SHD_SCR3_TRDDAPD ==
BCM54810_SHD_SCR3_TRDDAPD, so currently this if condition is redundant
and probably something else is wrong too:

	if (phydev->dev_flags & PHY_BRCM_DIS_TXCRXC_NOENRGY) {
		if (BRCM_PHY_MODEL(phydev) == PHY_ID_BCM54810 ||
		    BRCM_PHY_MODEL(phydev) == PHY_ID_BCM54811)
			val |= BCM54810_SHD_SCR3_TRDDAPD;
		else
			val |= BCM54XX_SHD_SCR3_TRDDAPD;
	}

I'm not sure what "TRDD" stands for, but my copy of the BCM5464R
datasheet shows both bits 2 as well as 8 as being reserved. I have
"CLK125 Output" in bit 0, "DLL Auto Power-Down" in bit 1, "SD/Energy
Detect Change" in bit 5, "TXC Disable" in bit 6, and that's about it.

But I think it doesn't matter what BCM5464R has, since this feature is
gated by PHY_BRCM_DIS_TXCRXC_NOENRGY.