linux-kernel - Re: [PATCH v3] net: phy: meson-gxl: Add generic dummy stubs for MMD register access

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Message-ID: <1j7cx32c4y.fsf@starbuckisacylon.baylibre.com>
Date:   Tue, 31 Jan 2023 11:59:40 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Heiner Kallweit <hkallweit1@...il.com>, cphealy@...il.com,
        andrew@...n.ch, linux@...linux.org.uk, davem@...emloft.net,
        neil.armstrong@...aro.org, khilman@...libre.com,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        jeremy.wang@...ogic.com
Cc:     Chris Healy <healych@...zon.com>
Subject: Re: [PATCH v3] net: phy: meson-gxl: Add generic dummy stubs for MMD
 register access


On Tue 31 Jan 2023 at 11:38, Heiner Kallweit <hkallweit1@...il.com> wrote:

> On 31.01.2023 11:05, Jerome Brunet wrote:
>> 
>> On Mon 30 Jan 2023 at 15:14, Chris Healy <cphealy@...il.com> wrote:
>> 
>>> From: Chris Healy <healych@...zon.com>
>>>
>>> The Meson G12A Internal PHY does not support standard IEEE MMD extended
>>> register access, therefore add generic dummy stubs to fail the read and
>>> write MMD calls. This is necessary to prevent the core PHY code from
>>> erroneously believing that EEE is supported by this PHY even though this
>>> PHY does not support EEE, as MMD register access returns all FFFFs.
>> 
>> This is definitely something that should be done, Thx !
>> 
>>>
>>> Fixes: 5c3407abb338 ("net: phy: meson-gxl: add g12a support")
>> 
>> This commit does not seems appropriate, especially since only the GXL ops
>> are changed, not the g12a variant.
>> 
> The diff is a little bit misleading. The patch affects the G12A PHY.
>
>> This brings a 2nd point, any reason for not changing the g12 variant ?
>> I'm fairly confident it does support EEE either.
>> 
> Supposedly it's a typo and you mean "doesn't". Neither Chris nor me

Indeed ;)

> have GXL HW and we didn't want to submit a patch just based on speculation.
>

Ah - Ok.
I've tested something similar recently while working on the PHY.
I confirm that both GXL and G12a should stub those calls.

... maybe in separate patches to help stable backports.

Do you want to handle this or should I ?

>>> Reviewed-by: Heiner Kallweit <hkallweit1@...il.com>
>>> Signed-off-by: Chris Healy <healych@...zon.com>
>>>

Reviewed-by: Jerome Brunet <jbrunet@...libre.com>

>>> ---
>>>
>>> Changes in v3:
>>> * Add reviewed-by
>>> Change in v2:
>>> * Add fixes tag
>>>
>>>  drivers/net/phy/meson-gxl.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/net/phy/meson-gxl.c b/drivers/net/phy/meson-gxl.c
>>> index c49062ad72c6..5e41658b1e2f 100644
>>> --- a/drivers/net/phy/meson-gxl.c
>>> +++ b/drivers/net/phy/meson-gxl.c
>>> @@ -271,6 +271,8 @@ static struct phy_driver meson_gxl_phy[] = {
>>>  		.handle_interrupt = meson_gxl_handle_interrupt,
>>>  		.suspend        = genphy_suspend,
>>>  		.resume         = genphy_resume,
>>> +		.read_mmd	= genphy_read_mmd_unsupported,
>>> +		.write_mmd	= genphy_write_mmd_unsupported,
>>>  	},
>>>  };
>>