[U-Boot] Handling different ethernhet phys on the same system.

* [U-Boot] Handling different ethernhet phys on the same system.
@ 2008-09-26 15:36 vb
  2008-09-26 15:42 ` Anton Vorontsov
  2008-09-26 17:03 ` Ben Warren
  0 siblings, 2 replies; 6+ messages in thread
From: vb @ 2008-09-26 15:36 UTC (permalink / raw)
  To: u-boot

Hello Ben,

I am trying to port u-boot on a system which deploys two different
types of ethernet PHYs, and don't see a good way of doing it with the
current sw structure.

There are concurrent implementations for supporting different PHYs,
and it looks like quite often bringing in a new etherent controller
brings in a duplicate PHY driver code. OTOH it is always presumed that
the same kind of phy is used on all ports.

I want to modify this scheme, but I don't want to go too far on a
tangent, as we here plan to integrate our changes back into the master
repository one of those days.

Here is what I suggest doing:

we introduce a concept of 'phy bus' - an MDIO bus for instance, and
'phy interface' which is the phy driver.

For illustration purpose, the phy bus could look like this:
struct phy_bus {
    int (*write)(u8 addr, u16 reg, u16 value);
    int (*read)(u8 addr, u16 reg, u16 *value);
}

and the driver would provide methods like

struct phy_driver {
   int (*reset)(struct phy_bus*, u8 addr))
   int (*init)(struct phy_bus*, u8 addr)
...
}

the set of methods could be fine tuned at any time obviously, the
important thing is that each method would receive the pointer to the
phy bus to be used to communicate with the device.

Then, in the ethernet device structure we would add two pointers: to
the bus serving the port and to the driver serving the port.

This would allow any new ethernet controller provide its own mdio bus
implementation and then use existing phy driver the same way any other
controller uses it. This would also allow to attach different phy
devices to different ethernet ports. And of course the multiple PHY
implementations won't be needed anymore, just one instance will serve
any ethernet device.

What do you think?

TIA,
Vadim

On Thu, Sep 25, 2008 at 11:09 PM, Ben Warren <biggerbadderben@gmail.com> wrote:
> Wolfgang Denk wrote:
>> Dear Ben,
>>
>> I just ran over this piece of code in NetLoop() [see "net/net.c"]:
>>
>>  286 int
>>  287 NetLoop(proto_t protocol)
>>  288 {
>>  ...
>>  322         eth_halt();
>>  323 #ifdef CONFIG_NET_MULTI
>>  324         eth_set_current();
>>  325 #endif
>>  326         if (eth_init(bd) < 0) {
>>  327                 eth_halt();
>>  328                 return(-1);
>>  329         }
>>
>> Am I reading this correctly that we  eth_halt()  and  eth_init()  the
>> network interface for each and every call to NetLoop?
>>
>>
> Yes, it looks that way.  Ripe for gutting.
>> This looks terribly inefficient to me - is there any rationale behind
>> this?
>>
>>
> Probably, but it escapes me.  It most certainly predates my involvement
> in this project.
>> Also, the eth_set_current() checking should IMHO be done  just  once,
>> before  we  start  a  network  transfer,  or  when we actually switch
>> interfaces, but not for each and every call to NetLoop() ?
>>
>>
> Maybe, but eth_set_current() is pretty lightweight.  NetLoop is only
> called when we start a network transfer, so this doesn't seem too
> egregious.  It could definitely stand to be refactored.
>> Best regards,
>>
>> Wolfgang Denk
>>
>>
> regards,
> Ben
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