On Tue, Jun 27, 2017 at 11:33:56AM +0100, Andre Przywara wrote:

Hi,

On 27/06/17 11:23, Icenowy Zheng wrote:

quoted

于 2017年6月27日 GMT+08:00 下午6:15:58, Andre Przywara [off-list ref] 写到:

quoted

Hi,

On 27/06/17 10:41, Maxime Ripard wrote:

quoted

On Tue, Jun 27, 2017 at 10:02:45AM +0100, Andre Przywara wrote:

quoted

Hi,

(CC:ing some people from that Rockchip dmwac series)

On 27/06/17 09:21, Corentin Labbe wrote:

quoted

On Tue, Jun 27, 2017 at 04:11:21PM +0800, Chen-Yu Tsai wrote:

quoted

On Tue, Jun 27, 2017 at 4:05 PM, Corentin Labbe
[off-list ref] wrote:

quoted

On Mon, Jun 26, 2017 at 01:18:23AM +0100, André Przywara wrote:

quoted

On 31/05/17 08:18, Corentin Labbe wrote:

quoted

The dwmac-sun8i is a heavy hacked version of stmmac hardware by
allwinner.
In fact the only common part is the descriptor management and

the first

quoted

quoted

quoted

quoted

quoted

quoted

quoted

register function.

Hi,

I know I am a bit late with this, but while adapting the U-Boot

driver

quoted

quoted

quoted

quoted

quoted

quoted

to the new binding I was wondering about the internal PHY

detection:

quoted

quoted

quoted

quoted

quoted

quoted

So here you seem to deduce the usage of the internal PHY by the

PHY

quoted

quoted

quoted

quoted

quoted

quoted

interface specified in the DT (MII = internal, RGMII =

external).

quoted

quoted

quoted

quoted

quoted

quoted

I think I raised this question before, but isn't it perfectly

legal for

quoted

quoted

quoted

quoted

quoted

quoted

a board to use MII with an external PHY even on those SoCs that

feature

quoted

quoted

quoted

quoted

quoted

quoted

an internal PHY?
On the first glance that does not make too much sense, but apart

from

quoted

quoted

quoted

quoted

quoted

quoted

not being the correct binding to describe all of the SoCs

features I see

quoted

quoted

quoted

quoted

quoted

quoted

two scenarios:
1) A board vendor might choose to not use the internal PHY

because it

quoted

quoted

quoted

quoted

quoted

quoted

has bugs, lacks features (configurability) or has other issues.

For

quoted

quoted

quoted

quoted

quoted

quoted

instance I have heard reports that the internal PHY makes the

SoC go

quoted

quoted

quoted

quoted

quoted

quoted

rather hot, possibly limiting the CPU frequency. By using an

external

quoted

quoted

quoted

quoted

quoted

quoted

MII PHY (which are still cheaper than RGMII PHYs) this can be

avoided.

quoted

quoted

quoted

quoted

quoted

quoted

2) A PHY does not necessarily need to be directly connected to
magnetics. Indeed quite some boards use (RG)MII to connect to a

switch

quoted

quoted

quoted

quoted

quoted

quoted

IC or some other network circuitry, for instance fibre

connectors.

quoted

quoted

quoted

quoted

quoted

quoted

So I was wondering if we would need an explicit:
      allwinner,use-internal-phy;
boolean DT property to signal the usage of the internal PHY?
Alternatively we could go with the negative version:
      allwinner,disable-internal-phy;

Or what about introducing a new "allwinner,internal-mii-phy"

compatible

quoted

quoted

quoted

quoted

quoted

quoted

string for the *PHY* node and use that?

I just want to avoid that we introduce a binding that causes us
headaches later. I think we can still fix this with a followup

patch

quoted

quoted

quoted

quoted

quoted

quoted

before the driver and its binding hit a release kernel.

Cheers,
Andre.

I just see some patch, where "phy-mode = internal" is valid.
I will try to find a way to use it

Can you provide a link?

https://lkml.org/lkml/2017/6/23/479

quoted

I'm not a fan of using phy-mode for this. There's no guarantee

what

quoted

quoted

quoted

quoted

mode the internal PHY uses. That's what phy-mode is for.

I can understand Chen-Yu's concerns, but ...

quoted

For each soc the internal PHY mode is know and setted in

emac_variant/internal_phy

quoted

quoted

quoted

So its not a problem.

that is true as well, at least for now.

So while I agree that having a separate property to indicate the

usage

quoted

quoted

of the internal PHY would be nice, I am bit tempted to use this

easier

quoted

quoted

approach and piggy back on the existing phy-mode property.

We're trying to fix an issue that works for now too.

If we want to consider future weird cases, then we must consider all
of them. And the phy mode changing is definitely not really far
fetched.

I agree with Chen-Yu, and I really feel like the compatible solution
you suggested would cover both your concerns, and ours.

So something like this?
	emac: emac@1c30000 {
	    compatible = "allwinner,sun8i-h3-emac";
	    ...
	    phy-mode = "mii";
	    phy-handle = <&int_mii_phy>;
	    ...

	    mdio: mdio {
               #address-cells = <1>;
               #size-cells = <0>;
               int_mii_phy: ethernet-phy@1 {
                   compatible = "allwinner,sun8i-h3-ephy";
                   syscon = <&syscon>;

The MAC still needs to set some bits of syscon register.

Yes, the syscon property needs also to be in the MAC node, that was
meant to be somewhere in the second "..." ;-)

But now since Chen-Yu mentioned that we need to set up the PHY *first*
to make it actually discoverable via MDIO, I wonder if we could change
this to:
1) have the DT as described here
2) Let the dwmac-sun8i driver peek into the node referenced by
phy-handle and check the compatible string there.
3) If that matches some allwinner internal PHY name, it sets up the PHY
to make it respond when the MDIO driver queries its bus.

That would be quite easy to do, and would be my implementation of
choice yes.

Or can a PHY driver set itself up (since we have clocks and resets
properties in there) *before* the MDIO bus gets scanned?
Chen-Yu's comment in the other mail hints at that this is not easily
possible.

Yeah, that's not easily doable, it would require your driver to probe
before your device has showed up, which is not quite what the driver
model is made like.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

-- 
You received this message because you are subscribed to the Google Groups "linux-sunxi" group.
To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit https://groups.google.com/d/optout.