lkml.org 
[lkml]   [2016]   [May]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH RFT 1/2] phylib: add device reset GPIO support
From
Date
Hello.

On 05/13/2016 10:18 PM, Sergei Shtylyov wrote:

>>> [we already talked about this patch in #armlinux, I'm now just
>>> forwarding my comments on the list. Background was that I sent an easier
>>> and less complete patch with the same idea. See
>>> http://patchwork.ozlabs.org/patch/621418/]
>>>
>>> [added Linus Walleij to Cc, there is a question for you/him below]
>>>
>>> On Fri, Apr 29, 2016 at 01:12:54AM +0300, Sergei Shtylyov wrote:
>>>> --- net-next.orig/Documentation/devicetree/bindings/net/phy.txt
>>>> +++ net-next/Documentation/devicetree/bindings/net/phy.txt
>>>> @@ -35,6 +35,8 @@ Optional Properties:
>>>> - broken-turn-around: If set, indicates the PHY device does not correctly
>>>> release the turn around line low at the end of a MDIO transaction.
>>>>
>>>> +- reset-gpios: The GPIO phandle and specifier for the PHY reset signal.
>>>> +
>>>> Example:
>>>>
>>>> ethernet-phy@0 {
>>>
>>> This is great.
>>>
>>>> Index: net-next/drivers/net/phy/at803x.c
>>>> ===================================================================
>>>> --- net-next.orig/drivers/net/phy/at803x.c
>>>> +++ net-next/drivers/net/phy/at803x.c
>>>> @@ -65,7 +65,6 @@ MODULE_LICENSE("GPL");
>>>> [...]
>>>
>>> My patch breaks this driver. I wasn't aware of it.
>>
>> I tried to be as careful as I could but still it looks that I didn't
>> succeed at that too...
>
> Hm, I'm starting to forget the vital details about my patch...
>
>> [...]
>>>> Index: net-next/drivers/net/phy/mdio_device.c
>>>> ===================================================================
>>>> --- net-next.orig/drivers/net/phy/mdio_device.c
>>>> +++ net-next/drivers/net/phy/mdio_device.c
>> [...]
>>>> @@ -117,9 +126,16 @@ static int mdio_probe(struct device *dev
>>>> struct mdio_driver *mdiodrv = to_mdio_driver(drv);
>>>> int err = 0;
>>>>
>>>> - if (mdiodrv->probe)
>>>> + if (mdiodrv->probe) {
>>>> + /* Deassert the reset signal */
>>>> + mdio_device_reset(mdiodev, 0);
>>>> +
>>>> err = mdiodrv->probe(mdiodev);
>>>>
>>>> + /* Assert the reset signal */
>>>> + mdio_device_reset(mdiodev, 1);
>>>
>>> I wonder if it's safe to do this in general. What if ->probe does
>>> something with the phy that is lost by resetting but that is relied on
>>> later?
>>
>> Well, I thought that config_init() method is designed for that but indeed
>> the LXT driver writes to BMCR in its probe() method and hence is broken.
>> Thank you for noticing...
>
> It's broken even without my patch. The phylib will cause a PHY soft reset

Only iff the config_init() method exists in the PHY driver...

> when attaching to the PHY device, so all BMCR programming dpone in the probe()
> method will be lost. My patch does make sense as is.

No, actually it doesn't. :-(

> Looks like I should alsolook into fixing lxt.c.

It took me to actually do a patch to understand my fault. Sigh... :-/

> Florian, what do you think?

Florian, is phy_init_hw() logic correct?

MBR, Sergei

\
 
 \ /
  Last update: 2016-05-14 23:21    [W:0.102 / U:0.868 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site