linux-kernel - Re: [PATCH] net: broadcom: Add PTP_1588_CLOCK_OPTIONAL dependency for BCMGENET under ARCH

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Message-Id: <10c264a3-019e-4473-9c20-9bb0c9af97c3@app.fastmail.com>
Date:   Tue, 29 Nov 2022 12:58:23 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Jakub Kicinski" <kuba@...nel.org>,
        "Richard Cochran" <richardcochran@...il.com>
Cc:     YueHaibing <yuehaibing@...wei.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric Dumazet" <edumazet@...gle.com>,
        "Paolo Abeni" <pabeni@...hat.com>,
        "Naresh Kamboju" <naresh.kamboju@...aro.org>,
        Netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Florian Fainelli" <f.fainelli@...il.com>
Subject: Re: [PATCH] net: broadcom: Add PTP_1588_CLOCK_OPTIONAL dependency for BCMGENET
 under ARCH_BCM2835

[Florian's broadcom.com address bounces, adding him to Cc
with his gmail address]

On Tue, Nov 29, 2022, at 12:56, Arnd Bergmann wrote:
> On Tue, Nov 29, 2022, at 04:18, Jakub Kicinski wrote:
>> On Fri, 25 Nov 2022 19:50:03 +0800 YueHaibing wrote:
>>> diff --git a/drivers/net/ethernet/broadcom/Kconfig b/drivers/net/ethernet/broadcom/Kconfig
>>> index 55dfdb34e37b..f4ca0c6c0f51 100644
>>> --- a/drivers/net/ethernet/broadcom/Kconfig
>>> +++ b/drivers/net/ethernet/broadcom/Kconfig
>>> @@ -71,13 +71,14 @@ config BCM63XX_ENET
>>>  config BCMGENET
>>>  	tristate "Broadcom GENET internal MAC support"
>>>  	depends on HAS_IOMEM
>>> +	depends on PTP_1588_CLOCK_OPTIONAL || !ARCH_BCM2835
>>>  	select MII
>>>  	select PHYLIB
>>>  	select FIXED_PHY
>>>  	select BCM7XXX_PHY
>>>  	select MDIO_BCM_UNIMAC
>>>  	select DIMLIB
>>> -	select BROADCOM_PHY if (ARCH_BCM2835 && PTP_1588_CLOCK_OPTIONAL)
>>> +	select BROADCOM_PHY if ARCH_BCM2835
>>>  	help
>>>  	  This driver supports the built-in Ethernet MACs found in the
>>>  	  Broadcom BCM7xxx Set Top Box family chipset.
>>
>> What's the code path that leads to the failure? I want to double check
>> that the driver is handling the PTP registration return codes correctly.
>> IIUC this is a source of misunderstandings in the PTP API.
>>
>> Richard, here's the original report:
>> https://lore.kernel.org/all/CA+G9fYvKfbJHcMZtybf_0Ru3+6fKPg9HwWTOhdCLrOBXMaeG1A@mail.gmail.com
>
> The original report was for a different bug that resulted in the
> BROADCOM_PHY driver not being selectable at all.
>
> The remaining problem here is this configuration:
>
> CONFIG_ARM=y
> CONFIG_BCM2835=y
> CONFIG_BCMGENET=y
> CONFIG_PTP_1588_CLOCK=m
> CONFIG_PTP_1588_CLOCK_OPTIONAL=m
> CONFIG_BROADCOM_PHY=m
>
> In this case, BCMGENET should 'select BROADCOM_PHY' to make the
> driver work correctly, but fails to do this because of the
> dependency. During early boot, this means it cannot access the
> PHY because that is in a loadable module, despite commit
> 99addbe31f55 ("net: broadcom: Select BROADCOM_PHY for BCMGENET")
> trying to ensure that it could.
>
> Note that many other ethernet drivers don't have this
> particular 'select' statement and just rely on the .config
> to contain a sensible set of drivers. In particular that
> is true when running 64-bit kernels on the same chip,
> which is now the normal configuration.
>
> The alternative to YueHaibing's fix would be to just revert
> 99addbe31f55 ("net: broadcom: Select BROADCOM_PHY for BCMGENET")
> and instead change the defconfig file to include the phy driver,
> as we do elsewhere.
>
>     Arnd