[PATCH] lan743x: Added fixed_phy support

[PATCH] lan743x: Added fixed_phy support

[Roelof Berg]

Utilizing the Linux fixed_phy layer allows a direct MII connection between
the lan7431 and a MII remote peer without any phy in between. We added a
section to .config that allows activating the linux fixed_phy layer in
lan743x. In fixed_phy mode there is no auto-negotiation, therefore the
baud rate and duplex mode needs to be configured by the user in .config
as well. For convenience also the MII mode can be configured now in
.config, independent from the activation of fixed_phy. The default
behavior ist to leave the MII mode unchanged (e.g. EEPROM configured).

Andrew Lunn kindly recommended to use phylink instead of fixed_phy. I
agree that this'd be better, unfortunately I have no test hardware here
that is equipped with a phy. Hence I used fixed_phy because this allows
me to create a patch that is 100%ly free fom side-effects to existing
systems that use a phy, when the new .config items remain untouched.

Test reproduction / application note:

1) The new .config settings baud, duplex and MII-mode need to be mirrored
by the user in the remote MII peer's configuration. For example a
Microchip KSZ9893 switch as a remote peer can be configured by resistors
to use the same baud/duplex/MII-mode as boot default.

2) In our setup (AE-LAN7431-KSZ9893) it was necessary to program the OTP
or EEPROM to activate the 125 MHz Clock of lan743x by:
ethtool -E enp1s0 magic 0x74a5 offset 0x1b value 0x24
ethtool -E enp1s0 magic 0x74a5 offset 0x1c value 0x2e
(Plus full EEPROM/OTP configuration with magic in byte 0.)

Signed-off-by: Roelof Berg <rberg@berg-solutions.de>
---
 drivers/net/ethernet/microchip/Kconfig        |  77 ++++++++++++-
 drivers/net/ethernet/microchip/lan743x_main.c | 107 +++++++++++++++++-
 drivers/net/ethernet/microchip/lan743x_main.h |   4 +
 3 files changed, 186 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/microchip/Kconfig b/drivers/net/ethernet/microchip/Kconfig
index 45fe41f3d9f3..642ef0f5208f 100644
--- a/drivers/net/ethernet/microchip/Kconfig
+++ b/drivers/net/ethernet/microchip/Kconfig
@@ -42,7 +42,7 @@ config ENCX24J600
       To compile this driver as a module, choose M here. The module will be
       called encx24j600.
 
-config LAN743X
+menuconfig LAN743X
 	tristate "LAN743x support"
 	depends on PCI
 	select PHYLIB
@@ -53,4 +53,79 @@ config LAN743X
 	  To compile this driver as a module, choose M here. The module will be
 	  called lan743x.
 
+# All the following symbols are dependent on LAN743X - do not repeat
+# that for each of the symbols.
+if LAN743X
+
+choice LAN743x_MII_MODE
+	prompt "MII operation mode"
+	default LAN743x_MII_MODE_DEFAULT
+	depends on LAN743X
+	help
+	 Defines the R/G/MII operation mode of the MAC of lan743.
+
+config LAN743x_MII_MODE_DEFAULT
+	bool "Device default"
+	help
+	 The existing internal device configuration, which may have come from
+	 EEPROM or OTP, will remain unchanged.
+
+config LAN743x_MII_MODE_RGMII
+	bool "RGMII"
+	help
+	 RGMII (Reduced GMII) will be enabled when the driver is loaded.
+
+config LAN743x_MII_MODE_GMII
+	bool "G/MII"
+	help
+	 GMII (in case of 100 mbit) or MII (in case of 10 mbit) will be enabled when
+	 the driver is loaded.
+
+endchoice
+
+config LAN743X_FIXED_PHY
+	bool "Direct R/G/MII connection without phy."
+	default n
+	select FIXED_PHY
+	help
+	 Direct R/G/MII connection to a remote MII device wo. any PHY in between.
+	 No mdio bus will be used in this case and no auto-negotiation takes place.
+	 The configuration settings below need to mirror the configuration of the
+	 remote MII device.
+
+choice
+	prompt "Bus speed"
+	default LAN743X_FIXED_PHY_SPEED_1000_MBIT
+	depends on LAN743X_FIXED_PHY
+	help
+	 Speed on the R/G/MII bus. This setting needs to mirror the settings of the
+	 remote MII device.
+
+config LAN743X_FIXED_PHY_SPEED_10_MBIT
+	bool "10 mbit"
+	help
+	 10 mbit speed on the R/G/MII bus.
+
+config LAN743X_FIXED_PHY_SPEED_100_MBIT
+	bool "100 mbit"
+	help
+	 100 mbit speed on the R/G/MII bus.
+
+config LAN743X_FIXED_PHY_SPEED_1000_MBIT
+	bool "1000 mbit"
+	help
+	 1 gbit speed on the R/G/MII bus.
+
+endchoice
+
+config LAN743X_FIXED_PHY_FULL_DUPLEX
+	bool "Full duplex"
+	default y
+	depends on LAN743X_FIXED_PHY
+	help
+	 Duplex mode on the R/G/MII bus. Enabled = full, disabled = half duplex. This
+	 setting needs to mirror the settings of the remote MII device.
+
+endif # LAN743X
+
 endif # NET_VENDOR_MICROCHIP
diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index a43140f7b5eb..02a82b90b389 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -9,6 +9,9 @@
 #include <linux/microchipphy.h>
 #include <linux/net_tstamp.h>
 #include <linux/phy.h>
+#ifdef CONFIG_LAN743X_FIXED_PHY
+#include <linux/phy_fixed.h>
+#endif
 #include <linux/rtnetlink.h>
 #include <linux/iopoll.h>
 #include <linux/crc16.h>
@@ -700,6 +703,7 @@ static int lan743x_dp_write(struct lan743x_adapter *adapter,
 	return ret;
 }
 
+#ifndef CONFIG_LAN743X_FIXED_PHY
 static u32 lan743x_mac_mii_access(u16 id, u16 index, int read)
 {
 	u32 ret;
@@ -768,6 +772,7 @@ static int lan743x_mdiobus_write(struct mii_bus *bus,
 	ret = lan743x_mac_mii_wait_till_not_busy(adapter);
 	return ret;
 }
+#endif
 
 static void lan743x_mac_set_address(struct lan743x_adapter *adapter,
 				    u8 *addr)
@@ -800,7 +805,47 @@ static int lan743x_mac_init(struct lan743x_adapter *adapter)
 
 	/* setup auto duplex, and speed detection */
 	data = lan743x_csr_read(adapter, MAC_CR);
+
+#ifdef LAN743x_MII_MODE_RGMII
+	/* RGMII */
+	data &= ~MAC_CR_MII_EN_;
+#endif
+#ifdef LAN743x_MII_MODE_GMII
+	/* Use GMII */
+	data |= MAC_CR_MII_EN_;
+#endif
+
+#ifdef CONFIG_LAN743X_FIXED_PHY
+	/* Disable auto negotiation */
+	data &= ~(MAC_CR_ADD_ | MAC_CR_ASD_);
+
+	/* Set duplex mode */
+#ifdef CONFIG_LAN743X_FIXED_PHY_FULL_DUPLEX
+	data |= MAC_CR_DPX_;
+#else
+	data &= ~MAC_CR_DPX_;
+#endif
+
+	/* Set bus speed */
+#if defined(CONFIG_LAN743X_FIXED_PHY_SPEED_10_MBIT)
+	data &= ~MAC_CR_CFG_H_;
+	data &= ~MAC_CR_CFG_L_;
+#elif defined(CONFIG_LAN743X_FIXED_PHY_SPEED_100_MBIT)
+	data &= ~MAC_CR_CFG_H_;
+	data |= MAC_CR_CFG_L_;
+#elif defined(CONFIG_LAN743X_FIXED_PHY_SPEED_1000_MBIT)
+	data |= MAC_CR_CFG_H_;
+	data |= MAC_CR_CFG_L_;
+#else
+	#error Unsupported CONFIG_LAN743X_FIXED_PHY_SPEED selection
+#endif
+
+#else
+
+ //Auto negotiation
 	data |= MAC_CR_ADD_ | MAC_CR_ASD_;
+#endif
+
 	data |= MAC_CR_CNTR_RST_;
 	lan743x_csr_write(adapter, MAC_CR, data);
 
@@ -973,7 +1018,11 @@ static void lan743x_phy_close(struct lan743x_adapter *adapter)
 	struct net_device *netdev = adapter->netdev;
 
 	phy_stop(netdev->phydev);
+#ifdef CONFIG_LAN743X_FIXED_PHY
+	fixed_phy_unregister(netdev->phydev);
+#else
 	phy_disconnect(netdev->phydev);
+#endif
 	netdev->phydev = NULL;
 }
 
@@ -982,16 +1031,55 @@ static int lan743x_phy_open(struct lan743x_adapter *adapter)
 	struct lan743x_phy *phy = &adapter->phy;
 	struct phy_device *phydev;
 	struct net_device *netdev;
+#ifdef CONFIG_LAN743X_FIXED_PHY
+	struct fixed_phy_status phy_status;
+#endif
 	int ret = -EIO;
 
 	netdev = adapter->netdev;
+
+#ifdef CONFIG_LAN743X_FIXED_PHY
+	phy_status.link = 1;
+	phy_status.speed =
+#if defined(CONFIG_LAN743X_FIXED_PHY_SPEED_10_MBIT)
+		10
+#elif defined(CONFIG_LAN743X_FIXED_PHY_SPEED_100_MBIT)
+		100
+#elif defined(CONFIG_LAN743X_FIXED_PHY_SPEED_1000_MBIT)
+		1000
+#endif
+		;
+	phy_status.duplex =
+#ifdef CONFIG_LAN743X_FIXED_PHY_FULL_DUPLEX
+		DUPLEX_FULL
+#else
+		DUPLEX_HALF
+#endif
+		;
+	phy_status.pause = 0;
+	phy_status.asym_pause = 0;
+
+	phydev = fixed_phy_register(PHY_POLL, &phy_status, 0);
+
+	if (!phydev || IS_ERR(phydev))
+		goto return_error;
+
+#else
+
 	phydev = phy_find_first(adapter->mdiobus);
 	if (!phydev)
 		goto return_error;
 
+#endif
+
 	ret = phy_connect_direct(netdev, phydev,
 				 lan743x_phy_link_status_change,
-				 PHY_INTERFACE_MODE_GMII);
+#ifdef CONFIG_LAN743x_RGMII
+				 PHY_INTERFACE_MODE_RGMII
+#else
+				 PHY_INTERFACE_MODE_GMII
+#endif
+				);
 	if (ret)
 		goto return_error;
 
@@ -1004,7 +1092,9 @@ static int lan743x_phy_open(struct lan743x_adapter *adapter)
 	phy->fc_autoneg = phydev->autoneg;
 
 	phy_start(phydev);
+#ifndef CONFIG_LAN743X_FIXED_PHY
 	phy_start_aneg(phydev);
+#endif
 	return 0;
 
 return_error:
@@ -2651,16 +2741,20 @@ static void lan743x_hardware_cleanup(struct lan743x_adapter *adapter)
 	lan743x_csr_write(adapter, INT_EN_CLR, 0xFFFFFFFF);
 }
 
+#ifndef CONFIG_LAN743X_FIXED_PHY
 static void lan743x_mdiobus_cleanup(struct lan743x_adapter *adapter)
 {
 	mdiobus_unregister(adapter->mdiobus);
 }
+#endif
 
 static void lan743x_full_cleanup(struct lan743x_adapter *adapter)
 {
 	unregister_netdev(adapter->netdev);
 
+#ifndef CONFIG_LAN743X_FIXED_PHY
 	lan743x_mdiobus_cleanup(adapter);
+#endif
 	lan743x_hardware_cleanup(adapter);
 	lan743x_pci_cleanup(adapter);
 }
@@ -2710,6 +2804,7 @@ static int lan743x_hardware_init(struct lan743x_adapter *adapter,
 	return 0;
 }
 
+#ifndef CONFIG_LAN743X_FIXED_PHY
 static int lan743x_mdiobus_init(struct lan743x_adapter *adapter)
 {
 	int ret;
@@ -2740,6 +2835,7 @@ static int lan743x_mdiobus_init(struct lan743x_adapter *adapter)
 return_error:
 	return ret;
 }
+#endif
 
 /* lan743x_pcidev_probe - Device Initialization Routine
  * @pdev: PCI device information struct
@@ -2784,9 +2880,11 @@ static int lan743x_pcidev_probe(struct pci_dev *pdev,
 	if (ret)
 		goto cleanup_pci;
 
+#ifndef CONFIG_LAN743X_FIXED_PHY
 	ret = lan743x_mdiobus_init(adapter);
 	if (ret)
 		goto cleanup_hardware;
+#endif
 
 	adapter->netdev->netdev_ops = &lan743x_netdev_ops;
 	adapter->netdev->ethtool_ops = &lan743x_ethtool_ops;
@@ -2798,11 +2896,18 @@ static int lan743x_pcidev_probe(struct pci_dev *pdev,
 
 	ret = register_netdev(adapter->netdev);
 	if (ret < 0)
+#ifdef CONFIG_LAN743X_FIXED_PHY
+		goto cleanup_hardware;
+#else
 		goto cleanup_mdiobus;
+#endif
+
 	return 0;
 
+#ifndef CONFIG_LAN743X_FIXED_PHY
 cleanup_mdiobus:
 	lan743x_mdiobus_cleanup(adapter);
+#endif
 
 cleanup_hardware:
 	lan743x_hardware_cleanup(adapter);
diff --git a/drivers/net/ethernet/microchip/lan743x_main.h b/drivers/net/ethernet/microchip/lan743x_main.h
index 3b02eeae5f45..e49f6b6cd440 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.h
+++ b/drivers/net/ethernet/microchip/lan743x_main.h
@@ -104,10 +104,14 @@
 	((value << 0) & FCT_FLOW_CTL_ON_THRESHOLD_)
 
 #define MAC_CR				(0x100)
+#define MAC_CR_MII_EN_			BIT(19)
 #define MAC_CR_EEE_EN_			BIT(17)
 #define MAC_CR_ADD_			BIT(12)
 #define MAC_CR_ASD_			BIT(11)
 #define MAC_CR_CNTR_RST_		BIT(5)
+#define MAC_CR_DPX_			BIT(3)
+#define MAC_CR_CFG_H_			BIT(2)
+#define MAC_CR_CFG_L_			BIT(1)
 #define MAC_CR_RST_			BIT(0)
 
 #define MAC_RX				(0x104)
-- 
2.20.1

Re: [PATCH] lan743x: Added fixed_phy support

[Andrew Lunn]

On Sun, Apr 26, 2020 at 01:43:18AM +0200, Roelof Berg wrote:
> +# All the following symbols are dependent on LAN743X - do not repeat
> +# that for each of the symbols.
> +if LAN743X
> +
> +choice LAN743x_MII_MODE
> +	prompt "MII operation mode"
> +	default LAN743x_MII_MODE_DEFAULT
> +	depends on LAN743X
> +	help
> +	 Defines the R/G/MII operation mode of the MAC of lan743.
> +
> +config LAN743x_MII_MODE_DEFAULT
> +	bool "Device default"
> +	help
> +	 The existing internal device configuration, which may have come from
> +	 EEPROM or OTP, will remain unchanged.
> +
> +config LAN743x_MII_MODE_RGMII
> +	bool "RGMII"
> +	help
> +	 RGMII (Reduced GMII) will be enabled when the driver is loaded.
> +
> +config LAN743x_MII_MODE_GMII
> +	bool "G/MII"
> +	help
> +	 GMII (in case of 100 mbit) or MII (in case of 10 mbit) will be enabled when
> +	 the driver is loaded.
> +
> +endchoice

Hi Roelof

You should not be putting this sort of configuration into Kconfig. You
want one kernel to be able to drive all LAN743x instances. Think of a
Debian kernel, etc.

So what are you trying to achieve here? What is the big picture?

You have a PCI device with a LAN743x connected to an Ethernet switch?
You need the MII interface between the LAN743x and the switch to be
configured to some specific speed? But you only want to do this for
your device. How can you identify your device? Do you set the PCI
vendor/device IDs to something unique?

You can add to the end of lan743x_pcidev_tbl[] your vendor/device
ID. In the probe function you can detect your own vendor/product ID
and then configure things as you need. 

    Andrew

Re: [PATCH] lan743x: Added fixed_phy support

[Roelof Berg]

Hello Andrew,

thanks for working together on this. Our target system is an embedded linux device for vehicles, that has all three components as single chips on one PCB: The MCU, the lan743x MAC and a KSZ9893 switch. The busses (PCIe, RGMII are fixed traces on the PCB without any sockets, no phy is between the MAC and the switch. So it is one big PCB with a lot of chips and a few Ethernet jacks for in-vehicle communication.

For an embedded systems vendor it is ok in such a case to configure the kernel to the needs of the system. Configuring is the easiest part, usually the kernel also needs to be patched as well :)

However, I see your concern that a runtime configuration would be more versatile. There are several methods for runtime detection instead of compile time ‚detection‘, e.g. lan743’s EEPROM, the PCI vendor-id as you mentioned (although we wouldn’t strictly need a vendor ID as we have everything on one PCB), or maybe the phy-enumeration if this is unambiguous, and the usual runtime-configuration-means (dev-fs etc.). Also the EEPROM of the lan743x can be used for hardware register configuration, possibly eliminating the need to configure things like the baud rate in the .config.

Four options:
a) We offer this kernel configuration and the next embedded system designer can use phyless MII mode.
b) We change this to a runtime configuration that somehow auto-detects that phyless MII mode is desired.
    (Then the EEPROM/OTP needs to provide baud rate, MII mode and duplex mode by user-register access).
c) We move the configuration of the phyless mode to somewhere like dev-fs
d) We avoid compiled fixed_phy and use a newer method. Like device-tree configuration of fixed_phy (is it working allready ?) or phylink as you originally suggested. Unfortunately I have no test-hardware here that uses a phy.
e) We leave this one away from the kernel if it is unlikely that other embedded systems would use lan8431 in direct (phyless) MII mode as well. Microchip (on cc) could know more about this likelihood.

Any votes from the list members of how to proceed ?

Thanks and have a nice day,
Roelof

> Am 26.04.2020 um 16:31 schrieb Andrew Lunn <andrew@lunn.ch>:
> 
> On Sun, Apr 26, 2020 at 01:43:18AM +0200, Roelof Berg wrote:
>> +# All the following symbols are dependent on LAN743X - do not repeat
>> +# that for each of the symbols.
>> +if LAN743X
>> +
>> +choice LAN743x_MII_MODE
>> +	prompt "MII operation mode"
>> +	default LAN743x_MII_MODE_DEFAULT
>> +	depends on LAN743X
>> +	help
>> +	 Defines the R/G/MII operation mode of the MAC of lan743.
>> +
>> +config LAN743x_MII_MODE_DEFAULT
>> +	bool "Device default"
>> +	help
>> +	 The existing internal device configuration, which may have come from
>> +	 EEPROM or OTP, will remain unchanged.
>> +
>> +config LAN743x_MII_MODE_RGMII
>> +	bool "RGMII"
>> +	help
>> +	 RGMII (Reduced GMII) will be enabled when the driver is loaded.
>> +
>> +config LAN743x_MII_MODE_GMII
>> +	bool "G/MII"
>> +	help
>> +	 GMII (in case of 100 mbit) or MII (in case of 10 mbit) will be enabled when
>> +	 the driver is loaded.
>> +
>> +endchoice
> 
> Hi Roelof
> 
> You should not be putting this sort of configuration into Kconfig. You
> want one kernel to be able to drive all LAN743x instances. Think of a
> Debian kernel, etc.
> 
> So what are you trying to achieve here? What is the big picture?
> 
> You have a PCI device with a LAN743x connected to an Ethernet switch?
> You need the MII interface between the LAN743x and the switch to be
> configured to some specific speed? But you only want to do this for
> your device. How can you identify your device? Do you set the PCI
> vendor/device IDs to something unique?
> 
> You can add to the end of lan743x_pcidev_tbl[] your vendor/device
> ID. In the probe function you can detect your own vendor/product ID
> and then configure things as you need. 
> 
>    Andrew
> 

Re: [PATCH] lan743x: Added fixed_phy support

[Andrew Lunn]

On Mon, Apr 27, 2020 at 11:37:07PM +0200, Roelof Berg wrote:
> Hello Andrew,
> 
> thanks for working together on this. Our target system is an embedded linux device for vehicles, that has all three components as single chips on one PCB: The MCU, the lan743x MAC and a KSZ9893 switch.

What is the MCU? ARM?

> Four options:
> a) We offer this kernel configuration and the next embedded system designer can use phyless MII mode.
> b) We change this to a runtime configuration that somehow auto-detects that phyless MII mode is desired.
>     (Then the EEPROM/OTP needs to provide baud rate, MII mode and duplex mode by user-register access).
> c) We move the configuration of the phyless mode to somewhere like dev-fs
> d) We avoid compiled fixed_phy and use a newer method. Like device-tree configuration of fixed_phy (is it working allready ?) or phylink as you originally suggested. Unfortunately I have no test-hardware here that uses a phy.
> e) We leave this one away from the kernel if it is unlikely that other embedded systems would use lan8431 in direct (phyless) MII mode as well. Microchip (on cc) could know more about this likelihood.

If you are using ARM, device tree is the way to go. In systems like
this, you know exactly which PCIe bus the lan743x will be hanging
off. So you can add a DT node for it. It is not done very often, but
look at arch/arm/boot/dts/imx6qdl-zii-rdu2.dtsi. That board has an
intel i210 on its PCIe bus, and we need a phandle for it. But you can
add any properties you want. For what you are doing, you should be
looking at:

Documentation/devicetree/bindings/net/ethernet-controller.yaml:

phy-mode and fixed-link.

	  Andrew

Re: [PATCH] lan743x: Added fixed_phy support

[Roelof Berg]

> What is the MCU? ARM?

Yes, i.mx6 with ARM.

> 
>> […]
> 
> If you are using ARM, device tree is the way to go.
> 	  Andrew
> 

Sounds reasonable, I’ll move the fixed_phy configuration for lan743x from .config to the device tree, thanks a lot Andrew.

Roelof

Re: [PATCH] lan743x: Added fixed_phy support / Question regarding proper devicetree

[Roelof Berg]

Working status: I added fixed_phy support to the Microchip lan743x ethernet driver and for upstream contribution I need to make it runtime configurable via the device tree.

Question:

There are, amongst other, the following devices on my target (i.mx6): 
/soc/aips-bus@2100000/ethernet@2188000
/soc/pcie@1ffc000

Where would I put my additional lan743x ethernet device in the device tree ?

a) /ethernet@0
    (Just a new root node.

b) /pci@0/ethernet@0
    (I would „invent“ pci@0 to reflect that the lan7431 is sitting on the first pci slot.

c) /soc/pcie@1ffc000/ethernet@0
    (That doesn’t feel right to me, it’s not a soc property. Or is it ?

Example:

        pci0 {
                ethernet@0 {
                        compatible = "rmtl-meu-hl“;
                        status = "okay“;
                        phy-connection-type = "rgmii“;
                        
                        fixed-link {
                                speed = <100>;
                                full-duplex;
                        };
                };
                
        }

Thanks a lot,
Roelof

> 
>> […] device tree is the way to go. […]
>> 
>> 	  Andrew
> 

Re: [PATCH] lan743x: Added fixed_phy support / Question regarding proper devicetree

[Andrew Lunn]

On Fri, May 01, 2020 at 08:09:05PM +0200, Roelof Berg wrote:
> Working status: I added fixed_phy support to the Microchip lan743x ethernet
> driver and for upstream contribution I need to make it runtime configurable via
> the device tree.
> 
> Question:
> 
> There are, amongst other, the following devices on my target (i.mx6): 
> /soc/aips-bus@2100000/ethernet@2188000
> /soc/pcie@1ffc000
> 
> Where would I put my additional lan743x ethernet device in the device tree ?

It is a child device of the PCIe host. So that decides where it goes
in the tree. The pcie bus should already be in the imx6 DTSI file. So
in your board specific dts file you want something like:

&pcie {
        host@0 {
                reg = <0 0 0 0 0>;

                #address-cells = <3>;
                #size-cells = <2>;

                ethernet: ethernet@0 {
                        reg = <0 0 0 0 0>;
			phy-connection-type = "rgmii";
                         
                        fixed-link {
                                speed = <100>;
                                full-duplex;
                        };
                };
         };
};

You will probably need to play around with this. It is not well
documented, there are few examples. I needed to put a few printk() in
the PCI core to get it working for the ZII boards.

    Andrew