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Date:   Tue, 19 Jul 2022 15:41:03 -0400
From:   Sean Anderson <sean.anderson@...o.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        Madalin Bucur <madalin.bucur@....com>,
        "David S . Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Andrew Lunn <andrew@...n.ch>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        UNGLinuxDriver@...rochip.com,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [RFC PATCH net-next 5/9] net: pcs: lynx: Use pcs_get_by_provider
 to get PCS



On 7/19/22 1:26 PM, Vladimir Oltean wrote:
> On Mon, Jul 11, 2022 at 12:05:15PM -0400, Sean Anderson wrote:
>> There is a common flow in several drivers where a lynx PCS is created
>> without a corresponding firmware node. Consolidate these into one helper
>> function. Because we control when the mdiodev is registered, we can add
>> a custom match function which will automatically bind our driver
>> (instead of using device_driver_attach).
>> 
>> Signed-off-by: Sean Anderson <sean.anderson@...o.com>
>> ---
>> 
>>  drivers/net/dsa/ocelot/felix_vsc9959.c        | 25 ++++---------------
>>  drivers/net/dsa/ocelot/seville_vsc9953.c      | 25 ++++---------------
>>  .../net/ethernet/freescale/enetc/enetc_pf.c   | 21 +++-------------
>>  drivers/net/pcs/pcs-lynx.c                    | 24 ++++++++++++++++++
>>  include/linux/pcs-lynx.h                      |  1 +
>>  5 files changed, 39 insertions(+), 57 deletions(-)
>> 
>> diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
>> index 57634e2296c0..0a756c25d5e8 100644
>> --- a/drivers/net/dsa/ocelot/felix_vsc9959.c
>> +++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
>> @@ -11,6 +11,7 @@
>>  #include <net/tc_act/tc_gate.h>
>>  #include <soc/mscc/ocelot.h>
>>  #include <linux/dsa/ocelot.h>
>> +#include <linux/pcs.h>
>>  #include <linux/pcs-lynx.h>
>>  #include <net/pkt_sched.h>
>>  #include <linux/iopoll.h>
>> @@ -1089,16 +1090,9 @@ static int vsc9959_mdio_bus_alloc(struct ocelot *ocelot)
>>  		if (ocelot_port->phy_mode == PHY_INTERFACE_MODE_INTERNAL)
>>  			continue;
>>  
>> -		mdio_device = mdio_device_create(felix->imdio, port);
>> -		if (IS_ERR(mdio_device))
>> +		phylink_pcs = lynx_pcs_create_on_bus(felix->imdio, port);
>> +		if (IS_ERR(phylink_pcs))
>>  			continue;
>> -
>> -		phylink_pcs = lynx_pcs_create(mdio_device);
>> -		if (IS_ERR(phylink_pcs)) {
>> -			mdio_device_free(mdio_device);
>> -			continue;
>> -		}
>> -
>>  		felix->pcs[port] = phylink_pcs;
>>  
>>  		dev_info(dev, "Found PCS at internal MDIO address %d\n", port);
>> @@ -1112,17 +1106,8 @@ static void vsc9959_mdio_bus_free(struct ocelot *ocelot)
>>  	struct felix *felix = ocelot_to_felix(ocelot);
>>  	int port;
>>  
>> -	for (port = 0; port < ocelot->num_phys_ports; port++) {
>> -		struct phylink_pcs *phylink_pcs = felix->pcs[port];
>> -		struct mdio_device *mdio_device;
>> -
>> -		if (!phylink_pcs)
>> -			continue;
>> -
>> -		mdio_device = lynx_get_mdio_device(phylink_pcs);
>> -		mdio_device_free(mdio_device);
>> -		lynx_pcs_destroy(phylink_pcs);
>> -	}
>> +	for (port = 0; port < ocelot->num_phys_ports; port++)
>> +		pcs_put(felix->pcs[port]);
>>  	mdiobus_unregister(felix->imdio);
>>  	mdiobus_free(felix->imdio);
>>  }
>> diff --git a/drivers/net/dsa/ocelot/seville_vsc9953.c b/drivers/net/dsa/ocelot/seville_vsc9953.c
>> index 8c52de5d0b02..9006dec85ef0 100644
>> --- a/drivers/net/dsa/ocelot/seville_vsc9953.c
>> +++ b/drivers/net/dsa/ocelot/seville_vsc9953.c
>> @@ -9,6 +9,7 @@
>>  #include <linux/mdio/mdio-mscc-miim.h>
>>  #include <linux/of_mdio.h>
>>  #include <linux/of_platform.h>
>> +#include <linux/pcs.h>
>>  #include <linux/pcs-lynx.h>
>>  #include <linux/dsa/ocelot.h>
>>  #include <linux/iopoll.h>
>> @@ -1044,16 +1045,9 @@ static int vsc9953_mdio_bus_alloc(struct ocelot *ocelot)
>>  		if (ocelot_port->phy_mode == PHY_INTERFACE_MODE_INTERNAL)
>>  			continue;
>>  
>> -		mdio_device = mdio_device_create(felix->imdio, addr);
>> -		if (IS_ERR(mdio_device))
>> +		phylink_pcs = lynx_pcs_create_on_bus(felix->imdio, addr);
>> +		if (IS_ERR(phylink_pcs))
>>  			continue;
>> -
>> -		phylink_pcs = lynx_pcs_create(mdio_device);
>> -		if (IS_ERR(phylink_pcs)) {
>> -			mdio_device_free(mdio_device);
>> -			continue;
>> -		}
>> -
>>  		felix->pcs[port] = phylink_pcs;
>>  
>>  		dev_info(dev, "Found PCS at internal MDIO address %d\n", addr);
>> @@ -1067,17 +1061,8 @@ static void vsc9953_mdio_bus_free(struct ocelot *ocelot)
>>  	struct felix *felix = ocelot_to_felix(ocelot);
>>  	int port;
>>  
>> -	for (port = 0; port < ocelot->num_phys_ports; port++) {
>> -		struct phylink_pcs *phylink_pcs = felix->pcs[port];
>> -		struct mdio_device *mdio_device;
>> -
>> -		if (!phylink_pcs)
>> -			continue;
>> -
>> -		mdio_device = lynx_get_mdio_device(phylink_pcs);
>> -		mdio_device_free(mdio_device);
>> -		lynx_pcs_destroy(phylink_pcs);
>> -	}
>> +	for (port = 0; port < ocelot->num_phys_ports; port++)
>> +		pcs_put(felix->pcs[port]);
>>  
>>  	/* mdiobus_unregister and mdiobus_free handled by devres */
>>  }
>> diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pf.c b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
>> index 8c923a93da88..8da7c8644e44 100644
>> --- a/drivers/net/ethernet/freescale/enetc/enetc_pf.c
>> +++ b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
>> @@ -8,6 +8,7 @@
>>  #include <linux/of_platform.h>
>>  #include <linux/of_mdio.h>
>>  #include <linux/of_net.h>
>> +#include <linux/pcs.h>
>>  #include <linux/pcs-lynx.h>
>>  #include "enetc_ierb.h"
>>  #include "enetc_pf.h"
>> @@ -827,7 +828,6 @@ static int enetc_imdio_create(struct enetc_pf *pf)
>>  	struct device *dev = &pf->si->pdev->dev;
>>  	struct enetc_mdio_priv *mdio_priv;
>>  	struct phylink_pcs *phylink_pcs;
>> -	struct mdio_device *mdio_device;
>>  	struct mii_bus *bus;
>>  	int err;
>>  
>> @@ -851,16 +851,8 @@ static int enetc_imdio_create(struct enetc_pf *pf)
>>  		goto free_mdio_bus;
>>  	}
>>  
>> -	mdio_device = mdio_device_create(bus, 0);
>> -	if (IS_ERR(mdio_device)) {
>> -		err = PTR_ERR(mdio_device);
>> -		dev_err(dev, "cannot create mdio device (%d)\n", err);
>> -		goto unregister_mdiobus;
>> -	}
>> -
>> -	phylink_pcs = lynx_pcs_create(mdio_device);
>> +	phylink_pcs = lynx_pcs_create_on_bus(bus, 0);
>>  	if (IS_ERR(phylink_pcs)) {
>> -		mdio_device_free(mdio_device);
>>  		err = PTR_ERR(phylink_pcs);
>>  		dev_err(dev, "cannot create lynx pcs (%d)\n", err);
>>  		goto unregister_mdiobus;
>> @@ -880,13 +872,8 @@ static int enetc_imdio_create(struct enetc_pf *pf)
>>  
>>  static void enetc_imdio_remove(struct enetc_pf *pf)
>>  {
>> -	struct mdio_device *mdio_device;
>> -
>> -	if (pf->pcs) {
>> -		mdio_device = lynx_get_mdio_device(pf->pcs);
>> -		mdio_device_free(mdio_device);
>> -		lynx_pcs_destroy(pf->pcs);
>> -	}
>> +	if (pf->pcs)
>> +		pcs_put(pf->pcs);
>>  	if (pf->imdio) {
>>  		mdiobus_unregister(pf->imdio);
>>  		mdiobus_free(pf->imdio);
>> diff --git a/drivers/net/pcs/pcs-lynx.c b/drivers/net/pcs/pcs-lynx.c
>> index 8272072698e4..adb9fd5ce72e 100644
>> --- a/drivers/net/pcs/pcs-lynx.c
>> +++ b/drivers/net/pcs/pcs-lynx.c
>> @@ -403,6 +403,30 @@ struct phylink_pcs *lynx_pcs_create(struct mdio_device *mdio)
>>  }
>>  EXPORT_SYMBOL(lynx_pcs_create);
>>  
>> +struct phylink_pcs *lynx_pcs_create_on_bus(struct mii_bus *bus, int addr)
>> +{
>> +	struct mdio_device *mdio;
>> +	struct phylink_pcs *pcs;
>> +	int err;
>> +
>> +	mdio = mdio_device_create(bus, addr);
>> +	if (IS_ERR(mdio))
>> +		return ERR_CAST(mdio);
>> +
>> +	mdio->bus_match = mdio_device_bus_match;
>> +	strncpy(mdio->modalias, "lynx-pcs", sizeof(mdio->modalias));
>> +	err = mdio_device_register(mdio);
> 
> Yeah, so the reason why mdio_device_register() fails with -EBUSY for the
> PCS devices created by felix_vsc9959.c is this:
> 
> int mdiobus_register_device(struct mdio_device *mdiodev)
> {
> 	int err;
> 
> 	if (mdiodev->bus->mdio_map[mdiodev->addr])
> 		return -EBUSY;
> 
> In other words, we already have an existing mdiodev on the bus at
> address mdiodev->addr. Funnily enough, that device is actually us.
> It was created at MDIO bus creation time, a dummy phydev that no one
> connects to, found by mdiobus_scan(). I knew this was taking place,
> but forgot/didn't realize the connection with this patch set, and that
> dummy phy_device was completely harmless until now.
> 
> I can suppress its creation like this:
> 
> From b1d1cd1625a27a62fd02598c7015b8ff0afdd28a Mon Sep 17 00:00:00 2001
> From: Vladimir Oltean <vladimir.oltean@....com>
> Date: Tue, 19 Jul 2022 20:15:52 +0300
> Subject: [PATCH] net: dsa: ocelot: suppress PHY device scanning on the
>  internal MDIO bus
> 
> This bus contains Lynx PCS devices, and if the lynx-pcs driver ever
> decided to call mdio_device_register(), it would fail due to
> mdiobus_scan() having created a dummy phydev for the same address
> (the PCS responds to standard clause 22 PHY ID registers and can
> therefore by autodetected by phylib which thinks it's a PHY).
> 
> On the Seville driver, things are a bit more complicated, since bus
> creation is handled by mscc_miim_setup() and that is shared with the
> dedicated mscc-miim driver. Suppress PHY scanning only for the Seville
> internal MDIO bus rather than for the whole mscc-miim driver, since we
> know that on NXP T1040, this bus only contains Lynx PCS devices.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
>  drivers/net/dsa/ocelot/felix_vsc9959.c   | 4 ++++
>  drivers/net/dsa/ocelot/seville_vsc9953.c | 6 +++++-
>  2 files changed, 9 insertions(+), 1 deletion(-)

Thanks! I'll pick this up for v2.

--Sean

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