[PATCH 1/4] net: macb: Fix regression breaking non-MDIO fixed-link PHYs

[PATCH 1/4] net: macb: Fix regression breaking non-MDIO fixed-link PHYs

[Ahmad Fatoum]

The referenced commit broke initializing macb on the EVB-KSZ9477 eval board.
There, of_mdiobus_register was called even for the fixed-link representing
the SPI-connected switch PHY, with the result that the driver attempts to
enumerate PHYs on a non-existent MDIO bus:

	libphy: MACB_mii_bus: probed
	mdio_bus f0028000.ethernet-ffffffff: fixed-link has invalid PHY address
	mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 0
        [snip]
	mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 31
	macb f0028000.ethernet: broken fixed-link specification

Cc: <stable@vger.kernel.org>
Fixes: 739de9a1563a ("net: macb: Reorganize macb_mii bringup")
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/net/ethernet/cadence/macb_main.c | 27 +++++++++++++++---------
 1 file changed, 17 insertions(+), 10 deletions(-)

Fixes since v1:
	Added one more error path for failing to register fixed-link
	Fixed a whitespace issue


diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index dc09f9a8a49b..ef6ce8691443 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -482,11 +482,6 @@ static int macb_mii_probe(struct net_device *dev)
 
 	if (np) {
 		if (of_phy_is_fixed_link(np)) {
-			if (of_phy_register_fixed_link(np) < 0) {
-				dev_err(&bp->pdev->dev,
-					"broken fixed-link specification\n");
-				return -ENODEV;
-			}
 			bp->phy_node = of_node_get(np);
 		} else {
 			bp->phy_node = of_parse_phandle(np, "phy-handle", 0);
@@ -569,7 +564,7 @@ static int macb_mii_init(struct macb *bp)
 {
 	struct macb_platform_data *pdata;
 	struct device_node *np;
-	int err;
+	int err = -ENXIO;
 
 	/* Enable management port */
 	macb_writel(bp, NCR, MACB_BIT(MPE));
@@ -592,12 +587,23 @@ static int macb_mii_init(struct macb *bp)
 	dev_set_drvdata(&bp->dev->dev, bp->mii_bus);
 
 	np = bp->pdev->dev.of_node;
-	if (pdata)
-		bp->mii_bus->phy_mask = pdata->phy_mask;
+	if (np && of_phy_is_fixed_link(np)) {
+		if (of_phy_register_fixed_link(np) < 0) {
+			dev_err(&bp->pdev->dev,
+				"broken fixed-link specification\n");
+			goto err_out_free_mdiobus;
+		}
+
+		err = mdiobus_register(bp->mii_bus);
+	} else {
+		if (pdata)
+			bp->mii_bus->phy_mask = pdata->phy_mask;
+
+		err = of_mdiobus_register(bp->mii_bus, np);
+	}
 
-	err = of_mdiobus_register(bp->mii_bus, np);
 	if (err)
-		goto err_out_free_mdiobus;
+		goto err_out_free_fixed_link;
 
 	err = macb_mii_probe(bp->dev);
 	if (err)
@@ -607,6 +613,7 @@ static int macb_mii_init(struct macb *bp)
 
 err_out_unregister_bus:
 	mdiobus_unregister(bp->mii_bus);
+err_out_free_fixed_link:
 	if (np && of_phy_is_fixed_link(np))
 		of_phy_deregister_fixed_link(np);
 err_out_free_mdiobus:
-- 
2.18.0

Re: [PATCH 1/4] net: macb: Fix regression breaking non-MDIO fixed-link PHYs

[Andrew Lunn]

On Mon, Aug 20, 2018 at 02:12:35PM +0200, Ahmad Fatoum wrote:
> The referenced commit broke initializing macb on the EVB-KSZ9477 eval board.
> There, of_mdiobus_register was called even for the fixed-link representing
> the SPI-connected switch PHY, with the result that the driver attempts to
> enumerate PHYs on a non-existent MDIO bus:
> 
> 	libphy: MACB_mii_bus: probed

So there are two different things here:

> 	mdio_bus f0028000.ethernet-ffffffff: fixed-link has invalid PHY address
> 	mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 0
>         [snip]
> 	mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 31

These are the result of the fixed-link being considered a PHY in
of_mdiobus_register(). Patch 2 fixes that, turns it into a single
warning.

> 	macb f0028000.ethernet: broken fixed-link specification

Why is of_phy_register_fixed_link(np) failing?

> 
> Cc: <stable@vger.kernel.org>
> Fixes: 739de9a1563a ("net: macb: Reorganize macb_mii bringup")
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/net/ethernet/cadence/macb_main.c | 27 +++++++++++++++---------
>  1 file changed, 17 insertions(+), 10 deletions(-)
> 
> Fixes since v1:
> 	Added one more error path for failing to register fixed-link
> 	Fixed a whitespace issue
> 
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index dc09f9a8a49b..ef6ce8691443 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -482,11 +482,6 @@ static int macb_mii_probe(struct net_device *dev)
>  
>  	if (np) {
>  		if (of_phy_is_fixed_link(np)) {
> -			if (of_phy_register_fixed_link(np) < 0) {
> -				dev_err(&bp->pdev->dev,
> -					"broken fixed-link specification\n");
> -				return -ENODEV;
> -			}

As a separate patch, please can you use the error code which
of_phy_register_fixed_link() returns, not -ENODEV. It is possible it
is returning EPROBE_DEFER.

   Andrew

Re: [PATCH 1/4] net: macb: Fix regression breaking non-MDIO fixed-link PHYs

[Ahmad Fatoum]

On 08/20/2018 03:55 PM, Andrew Lunn wrote:
> Why is of_phy_register_fixed_link(np) failing?

Apparently, the fixed-link's gpio's FLAG_REQUESTED bit remained set
causing gpiod_request_commit to return -EBUSY in (v4.18.0):

[<c0667750>] (gpiod_request_commit) from [<c066890c>] (gpiod_request+0x64/0x88)             
[<c066890c>] (gpiod_request) from [<c066a338>] (gpiod_get_from_of_node+0x48/0x13c)          
[<c066a338>] (gpiod_get_from_of_node) from [<c094b92c>] (mdiobus_register_device+0x70/0x124)
[<c094b92c>] (mdiobus_register_device) from [<c0949d2c>] (phy_device_register+0xc/0xa0)     
[<c0949d2c>] (phy_device_register) from [<c094e824>] (fixed_phy_register+0xe8/0x1f8)        
[<c094e824>] (fixed_phy_register) from [<c0b84260>] (of_phy_register_fixed_link+0x150/0x1e4)
[<c0b84260>] (of_phy_register_fixed_link) from [<c0964908>] (macb_probe+0x548/0xa7c)        
[<c0964908>] (macb_probe) from [<c086ebec>] (platform_drv_probe+0x48/0x98)                  

But that's a separate issue, I'll remove this line from the commit message...

Re: [PATCH 1/4] net: macb: Fix regression breaking non-MDIO fixed-link PHYs

[Andrew Lunn]

On Mon, Aug 20, 2018 at 05:56:53PM +0200, Ahmad Fatoum wrote:
> On 08/20/2018 03:55 PM, Andrew Lunn wrote:
> > Why is of_phy_register_fixed_link(np) failing?
> 
> Apparently, the fixed-link's gpio's FLAG_REQUESTED bit remained set
> causing gpiod_request_commit to return -EBUSY in (v4.18.0):
> 
> [<c0667750>] (gpiod_request_commit) from [<c066890c>] (gpiod_request+0x64/0x88)             
> [<c066890c>] (gpiod_request) from [<c066a338>] (gpiod_get_from_of_node+0x48/0x13c)          
> [<c066a338>] (gpiod_get_from_of_node) from [<c094b92c>] (mdiobus_register_device+0x70/0x124)
> [<c094b92c>] (mdiobus_register_device) from [<c0949d2c>] (phy_device_register+0xc/0xa0)     
> [<c0949d2c>] (phy_device_register) from [<c094e824>] (fixed_phy_register+0xe8/0x1f8)        
> [<c094e824>] (fixed_phy_register) from [<c0b84260>] (of_phy_register_fixed_link+0x150/0x1e4)
> [<c0b84260>] (of_phy_register_fixed_link) from [<c0964908>] (macb_probe+0x548/0xa7c)        
> [<c0964908>] (macb_probe) from [<c086ebec>] (platform_drv_probe+0x48/0x98)                  
> 
> But that's a separate issue, I'll remove this line from the commit message...

I would actually say, this is your real issue here. The warnings are
annoying, but i don't think they are fatal. This -EBUSY is what is
stopping the driver from loading, causing the real regression.

I'm guessing, but i think you will find the driver is loading once,
but hits a EPROBE_DEFFER condition, after getting the gpio. It does
not release the gpio correctly. Sometime later, it gets loaded again,
but the gpio is now in use, so you get the -EBUSY.

So check the error paths, and make sure cleanup is being done correct.
It could also be a phylib core bug...

   Andrew