[PATCH] net: phy: Add config option to specify external switch port to be used if switch is used as PHY

[PATCH] net: phy: Add config option to specify external switch port to be used if switch is used as PHY

[Lambrecht Jürgen]

Hello,

In our embedded designs, this is a useful patch. Maybe it can be useful 
for somebody else too.
Or maybe there are already better solutions?
I know I could also write a driver for our switch, but that is too much 
effort just to select the active port.

Kind regards,
Jürgen

   In embedded design, instead of a PHY, sometimes a switch is used that
           behaves as a PHY through its MII port. For example to use a daisy
           chain network configuration instead of an expensive star config.
           In that case, many phy ports are available, but only 1 should 
be used
           to check link status, and not the first one available as is 
the case
           without this configuration (that is, set to its default value 0).
           So this options specifies the switch port number to be used 
to check
           link status, because if the link is down, no data is sent by the
           TCP/IP stack.

Signed-off-by: Jürgen Lambrecht <J.Lambrecht@televic.com>
---
  drivers/net/phy/Kconfig    |   14 ++++++++++++++
  drivers/net/phy/mdio_bus.c |    9 +++++++++
  2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index a702443..554561f 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -13,6 +13,20 @@ menuconfig PHYLIB

  if PHYLIB

+config SWITCH_PHY
+       int "External switch port to be used if switch is used as PHY"
+       default "0"
+       help
+         In embedded design, instead of a PHY, sometimes a switch is 
used that
+         behaves as a PHY through its MII port. For example to use a daisy
+         chain network configuration instead of an expensive star config.
+         In that case, many phy ports are available, but only 1 should 
be used
+         to check link status, and not the first one available as is 
the case
+         without this configuration (that is, set to its default value 0).
+         So this options specifies the switch port number to be used to 
check
+         link status, because if the link is down, no data is sent by the
+         TCP/IP stack.
+
  comment "MII PHY device drivers"

  config MARVELL_PHY
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 6c58da2..016437a 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -112,7 +112,14 @@ int mdiobus_register(struct mii_bus *bus)
         if (bus->reset)
                 bus->reset(bus);

+       /* The config below is always availble with CONFIG_PHYLIB. If 0, the
+          behavior is as before without this patch (or P0 of the switch is
+          taken because it is the first one found). */
+#if CONFIG_SWITCH_PHY
+       i = CONFIG_SWITCH_PHY;
+#else
         for (i = 0; i < PHY_MAX_ADDR; i++) {
+#endif
                 if ((bus->phy_mask & (1 << i)) == 0) {
                         struct phy_device *phydev;

@@ -122,7 +129,9 @@ int mdiobus_register(struct mii_bus *bus)
                                 goto error;
                         }
                 }
+#if !CONFIG_SWITCH_PHY
         }
+#endif

         bus->state = MDIOBUS_REGISTERED;
         pr_info("%s: probed\n", bus->name);
--
1.7.1

Re: [PATCH] net: phy: Add config option to specify external switch port to be used if switch is used as PHY

[Florian Fainelli]

Hello Jurgen,

On Thursday 08 September 2011 08:54:07 Lambrecht Jürgen wrote:
> Hello,
> 
> In our embedded designs, this is a useful patch. Maybe it can be useful
> for somebody else too.
> Or maybe there are already better solutions?
> I know I could also write a driver for our switch, but that is too much
> effort just to select the active port.

This is not going to work well with all switches out there. You could use the 
fixed-PHY driver to make your ethernet driver see the link as always up between 
the MAC and switch CPU port.

A better solution would be to have proper switch drivers and user-space, which 
reminds me that we (OpenWrt) should at some point propose our switch drivers 
[1] for review.

[1]: 
https://dev.openwrt.org/browser/trunk/target/linux/generic/files/drivers/net/phy/

> 
> Kind regards,
> Jürgen
> 
>    In embedded design, instead of a PHY, sometimes a switch is used that
>            behaves as a PHY through its MII port. For example to use a
> daisy chain network configuration instead of an expensive star config. In
> that case, many phy ports are available, but only 1 should be used
>            to check link status, and not the first one available as is
> the case
>            without this configuration (that is, set to its default value
> 0). So this options specifies the switch port number to be used to check
>            link status, because if the link is down, no data is sent by the
>            TCP/IP stack.
> 
> Signed-off-by: Jürgen Lambrecht <J.Lambrecht@televic.com>
> ---
>   drivers/net/phy/Kconfig    |   14 ++++++++++++++
>   drivers/net/phy/mdio_bus.c |    9 +++++++++
>   2 files changed, 23 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
> index a702443..554561f 100644
> --- a/drivers/net/phy/Kconfig
> +++ b/drivers/net/phy/Kconfig
> @@ -13,6 +13,20 @@ menuconfig PHYLIB
> 
>   if PHYLIB
> 
> +config SWITCH_PHY
> +       int "External switch port to be used if switch is used as PHY"
> +       default "0"
> +       help
> +         In embedded design, instead of a PHY, sometimes a switch is
> used that
> +         behaves as a PHY through its MII port. For example to use a daisy
> +         chain network configuration instead of an expensive star config.
> +         In that case, many phy ports are available, but only 1 should
> be used
> +         to check link status, and not the first one available as is
> the case
> +         without this configuration (that is, set to its default value 0).
> +         So this options specifies the switch port number to be used to
> check
> +         link status, because if the link is down, no data is sent by the
> +         TCP/IP stack.
> +
>   comment "MII PHY device drivers"
> 
>   config MARVELL_PHY
> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> index 6c58da2..016437a 100644
> --- a/drivers/net/phy/mdio_bus.c
> +++ b/drivers/net/phy/mdio_bus.c
> @@ -112,7 +112,14 @@ int mdiobus_register(struct mii_bus *bus)
>          if (bus->reset)
>                  bus->reset(bus);
> 
> +       /* The config below is always availble with CONFIG_PHYLIB. If 0,
> the +          behavior is as before without this patch (or P0 of the
> switch is +          taken because it is the first one found). */
> +#if CONFIG_SWITCH_PHY
> +       i = CONFIG_SWITCH_PHY;
> +#else
>          for (i = 0; i < PHY_MAX_ADDR; i++) {
> +#endif
>                  if ((bus->phy_mask & (1 << i)) == 0) {
>                          struct phy_device *phydev;
> 
> @@ -122,7 +129,9 @@ int mdiobus_register(struct mii_bus *bus)
>                                  goto error;
>                          }
>                  }
> +#if !CONFIG_SWITCH_PHY
>          }
> +#endif
> 
>          bus->state = MDIOBUS_REGISTERED;
>          pr_info("%s: probed\n", bus->name);
> --
> 1.7.1
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-- 
Florian

Re: [PATCH] net: phy: Add config option to specify external switch port to be used if switch is used as PHY

[Lambrecht Jürgen]

On 09/08/2011 10:39 AM, Florian Fainelli wrote:
>
> Hello Jurgen,
>
> On Thursday 08 September 2011 08:54:07 Lambrecht J

Re: [PATCH] net: phy: Add config option to specify external switch port to be used if switch is used as PHY

[Francois Romieu]

Lambrecht Jürgen <J.Lambrecht@TELEVIC.com> :
[...]
> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> index 6c58da2..016437a 100644
> --- a/drivers/net/phy/mdio_bus.c
> +++ b/drivers/net/phy/mdio_bus.c
> @@ -112,7 +112,14 @@ int mdiobus_register(struct mii_bus *bus)
>          if (bus->reset)
>                  bus->reset(bus);
> 
> +       /* The config below is always availble with CONFIG_PHYLIB. If 0, the
> +          behavior is as before without this patch (or P0 of the switch is
> +          taken because it is the first one found). */
> +#if CONFIG_SWITCH_PHY
> +       i = CONFIG_SWITCH_PHY;
> +#else
>          for (i = 0; i < PHY_MAX_ADDR; i++) {
> +#endif
>                  if ((bus->phy_mask & (1 << i)) == 0) {
>                          struct phy_device *phydev;

This config option may help your platform but it is nowhere reusable on a
slightly different one (each mii_bus behavior is changed).

Which driver(s) do you use that you can not set phy_mask directly ?

-- 
Ueimor

Re: [PATCH] net: phy: Add config option to specify external switch port to be used if switch is used as PHY

[Lambrecht Jürgen]

On 09/08/2011 12:13 PM, Francois Romieu wrote:
>
> Lambrecht Jürgen <J.Lambrecht@TELEVIC.com> :
> [...]
> > diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> > index 6c58da2..016437a 100644
> > --- a/drivers/net/phy/mdio_bus.c
> > +++ b/drivers/net/phy/mdio_bus.c
> > @@ -112,7 +112,14 @@ int mdiobus_register(struct mii_bus *bus)
> >          if (bus->reset)
> >                  bus->reset(bus);
> >
> > +       /* The config below is always availble with CONFIG_PHYLIB. 
> If 0, the
> > +          behavior is as before without this patch (or P0 of the 
> switch is
> > +          taken because it is the first one found). */
> > +#if CONFIG_SWITCH_PHY
> > +       i = CONFIG_SWITCH_PHY;
> > +#else
> >          for (i = 0; i < PHY_MAX_ADDR; i++) {
> > +#endif
> >                  if ((bus->phy_mask & (1 << i)) == 0) {
> >                          struct phy_device *phydev;
>
> This config option may help your platform but it is nowhere reusable on a
> slightly different one (each mii_bus behavior is changed).
>
> Which driver(s) do you use that you can not set phy_mask directly ?
>
The HW driver is 'FEC' for iMX Ethernet. For the PHY, just MII and PHYLIB.
I am rather new to linux, didn't knew phy_mask. Checked it now, and is 
not set in fec.c.
You mean then to patch drivers/net/fec.c in the same way (as my current 
patch) to set the phy_mask instead (via menuconfig, or in the platform 
init)?

Thanks for your reply,
Jürgen
>
>
> --
> Ueimor
>


-- 
Jürgen Lambrecht
R&D Associate
Tel: +32 (0)51 303045    Fax: +32 (0)51 310670
http://www.televic-rail.com
Televic Rail NV - Leo Bekaertlaan 1 - 8870 Izegem - Belgium
Company number 0825.539.581 - RPR Kortrijk

Re: [PATCH] net: phy: Add config option to specify external switch port to be used if switch is used as PHY

[Francois Romieu]

Lambrecht Jürgen <J.Lambrecht@TELEVIC.com> :
> On 09/08/2011 12:13 PM, Francois Romieu wrote:
[...]
> > Which driver(s) do you use that you can not set phy_mask directly ?
> >
> The HW driver is 'FEC' for iMX Ethernet. For the PHY, just MII and PHYLIB.
> I am rather new to linux, didn't knew phy_mask. Checked it now, and is 
> not set in fec.c.
> You mean then to patch drivers/net/fec.c in the same way (as my current 
> patch) to set the phy_mask instead (via menuconfig, or in the platform 
> init)?

It is not my area but I would have drivers/net/fec.c::fec_devtype.driver_data
point to a real struct where the relevant phy_mask and the current quirks
are stored, then add a new entry in fec_devtype and a reference to it
(Kconfig + platform init) somewhere below arch/arm/plat-mxc.

Freescale's application note suggests that the MX25 fec allows some freedom
for the implementation of the media interface. So it may not be overkill.

-- 
Ueimor