linux-kernel - Re: v2 [PATCH 1/1] net: phy: marvell: avoid bringing down fibre link when autoneg is bypassed

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Message-ID: <4f4baf9c-b9e9-4add-89d4-75f3150264b0@intel.com>
Date: Thu, 3 Oct 2024 08:53:50 +0200
From: Mateusz Polchlopek <mateusz.polchlopek@...el.com>
To: Qingtao Cao <qingtao.cao.au@...il.com>
CC: Qingtao Cao <qingtao.cao@...i.com>, Andrew Lunn <andrew@...n.ch>, "Heiner
 Kallweit" <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: v2 [PATCH 1/1] net: phy: marvell: avoid bringing down fibre link
 when autoneg is bypassed


On 10/3/2024 6:45 AM, Qingtao Cao wrote:
> On 88E151x the SGMII autoneg bypass mode defaults to be enabled. When it is
> activated, the device assumes a link-up status with existing configuration
> in BMCR, avoid bringing down the fibre link in this case
> 
> Test case:
> 1. Two 88E151x connected with SFP, both enable autoneg, link is up with speed
>     1000M

checkpatch.pl complains about this line, it exceeds 75 chars allowed for
commit msg. Please adjust.

> 2. Disable autoneg on one device and explicitly set its speed to 1000M
> 3. The fibre link can still up with this change, otherwise not.
> 
> Signed-off-by: Qingtao Cao <qingtao.cao@...i.com>
> ---
>   drivers/net/phy/marvell.c | 23 ++++++++++++++++++++++-
>   1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/marvell.c b/drivers/net/phy/marvell.c
> index 9964bf3dea2f..e3a8ad8b08dd 100644
> --- a/drivers/net/phy/marvell.c
> +++ b/drivers/net/phy/marvell.c
> @@ -195,6 +195,10 @@
>   
>   #define MII_88E1510_MSCR_2		0x15
>   
> +#define MII_88E1510_FSCR2		0x1a

Please use GENMASK_ULL for creating mask.

> +#define MII_88E1510_FSCR2_BYPASS_ENABLE	BIT(6)
> +#define MII_88E1510_FSCR2_BYPASS_STATUS	BIT(5)
> +
>   #define MII_VCT5_TX_RX_MDI0_COUPLING	0x10
>   #define MII_VCT5_TX_RX_MDI1_COUPLING	0x11
>   #define MII_VCT5_TX_RX_MDI2_COUPLING	0x12
> @@ -1623,11 +1627,28 @@ static void fiber_lpa_mod_linkmode_lpa_t(unsigned long *advertising, u32 lpa)
>   static int marvell_read_status_page_an(struct phy_device *phydev,
>   				       int fiber, int status)
>   {
> +	int fscr2;
>   	int lpa;
>   	int err;
>   
>   	if (!(status & MII_M1011_PHY_STATUS_RESOLVED)) {
> -		phydev->link = 0;
> +		if (!fiber) {
> +			phydev->link = 0;
> +		} else {
> +			fscr2 = phy_read(phydev, MII_88E1510_FSCR2);
> +			if (fscr2 > 0) {
> +				if ((fscr2 & MII_88E1510_FSCR2_BYPASS_ENABLE) &&
> +				    (fscr2 & MII_88E1510_FSCR2_BYPASS_STATUS)) {
> +					if (genphy_read_status_fixed(phydev) < 0)
> +						phydev->link = 0;
> +				} else {
> +					phydev->link = 0;
> +				}
> +			} else {
> +				phydev->link = 0;
> +			}
> +		}
> +
>   		return 0;
>   	}
>   

So many levels of indentation... Couldn't it be merged somehow? I do not
know, maybe create local variable, store the current state of
phydev->link, then set phydev->link = 0 and restore it from local
variable only if (fiber && fscr2 > 0 && (fscr2 &
MII_88E1510_FSCR2_BYPASS_ENABLE) && (fscr2 & 
MII_88E1510_FSCR2_BYPASS_STATUS) && genphy_read_status_fixed(phydev) >=0 
) ...

or other way? Now you have 5 (!) levels of indentation and almost
everywhere you just set phydev->link to 0 depends on the condition.


BTW. We put "v2" inside the tag in the topic and specify the tree, so
instead of:
v2 [PATCH 1/1] net: phy: marvell: avoid bringing down fibre link when 
autoneg is bypassed

it should be:
[PATCH net-next v2 1/1] net: phy: marvell: avoid bringing down fibre 
link when autoneg is bypassed