lkml.org 
[lkml]   [2014]   [Aug]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/3] ARM: zynq: DT: Add Ethernet phys
On 08/25/2014 10:46 AM, Jason Gunthorpe wrote:
> On Fri, Aug 22, 2014 at 01:47:09PM -0700, Florian Fainelli wrote:
>
>>> - the ID based strings seem to be not needed since, IIUC, the core
>>> reads the ID from the PHY and uses it, so I just left it out not
>>> trying to figure out how to obtain the correct ID
>>
>> It is not needed, but it is one way to specify a PHY device if you do
>> not know what compatible string to use instead.
>
> No, it is a way to specify a PHY device if the kernel can't auto probe
> the Phy ID.
>
> Last I checked, the kernel doesn't support plain text compatible
> strings for phys - everything is driven on the phy id, either auto
> probed or specified in the DT.

That's right. Some PHY drivers might be relying on specific compatible
strings though, but not the core PHY library that probes and maps a
driver to a PHY node.

>
>>> - the marvell compatible strings are used in our vendor tree. They
>>> aren't used anywhere but in our vendor tree. I though keeping them is
>>> nice since it identifies the PHY fully. And in case that level of
>>> detail is needed at some point it is already there.
>>
>> And this is the recommended way to do it in case we ever need to key a
>> software decision based on the hardware.
>
> All compatible strings need to be documented.
>
> .. and they need to encode more information than you get from the phy
> id - die revsision, package option, functional options, voltage
> codes. Etc.
>
> .. and they actually need to be *right*

Agreed.

>
> An example: The kernel reports 88E1318S for all four chips in that
> family, AFAIK you have to read the package marking to figure out which
> you have (it is the same die, with options switched on/off at
> packaging time). People have already posted patches trying to
> helpfully add a 'marvell,88E1318S' compatible string based on kernel
> output. Except it is wrong, it isn't actually the '8S version in the
> HW.
>
> Even worse, Marvell has a whole series of socket compatible phys. Just
> because the board the DT author looked at has a '318, doesn't mean
> that every board ever made will. We've actually already been switching
> between the 318 and 318S for production depending on which has part
> availability.
>
> Basically: don't try to override self-discoverable hardware in DT
> without a really good reason.

I think that's a very good point, at the very least let's use a
compatible string that contains the full 32-bits PHY OUI.

Thanks
--
Florian


\
 
 \ /
  Last update: 2014-08-25 22:41    [W:1.574 / U:1.416 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site