[PATCH net] net: broadcom: Imply BROADCOM_PHY for BCMGENET

[PATCH net] net: broadcom: Imply BROADCOM_PHY for BCMGENET

[Florian Fainelli]

The GENET controller on the Raspberry Pi 4 (2711) is typically
interfaced with an external Broadcom PHY via a RGMII electrical
interface. To make sure that delays are properly configured at the PHY
side, ensure that we get a chance to have the dedicated Broadcom PHY
driver (CONFIG_BROADCOM_PHY) enabled for this to happen.

Fixes: 402482a6a78e ("net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB_CTRL when not needed")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
David,

I would like Marek to indicate whether he is okay or not with this
change. Thanks!

 drivers/net/ethernet/broadcom/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/broadcom/Kconfig b/drivers/net/ethernet/broadcom/Kconfig
index 53055ce5dfd6..8a70b9152f7c 100644
--- a/drivers/net/ethernet/broadcom/Kconfig
+++ b/drivers/net/ethernet/broadcom/Kconfig
@@ -69,6 +69,7 @@ config BCMGENET
 	select BCM7XXX_PHY
 	select MDIO_BCM_UNIMAC
 	select DIMLIB
+	imply BROADCOM_PHY if ARCH_BCM2835
 	help
 	  This driver supports the built-in Ethernet MACs found in the
 	  Broadcom BCM7xxx Set Top Box family chipset.
-- 
2.17.1

Re: [PATCH net] net: broadcom: Imply BROADCOM_PHY for BCMGENET

[Geert Uytterhoeven]

Hi Florian,

Thanks for your patch!

On Sat, May 9, 2020 at 12:32 AM Florian Fainelli <f.fainelli@gmail.com> wrote:
> The GENET controller on the Raspberry Pi 4 (2711) is typically
> interfaced with an external Broadcom PHY via a RGMII electrical
> interface. To make sure that delays are properly configured at the PHY
> side, ensure that we get a chance to have the dedicated Broadcom PHY
> driver (CONFIG_BROADCOM_PHY) enabled for this to happen.

I guess it can be interfaced to a different external PHY, too?

> Fixes: 402482a6a78e ("net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB_CTRL when not needed")
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

> --- a/drivers/net/ethernet/broadcom/Kconfig
> +++ b/drivers/net/ethernet/broadcom/Kconfig
> @@ -69,6 +69,7 @@ config BCMGENET
>         select BCM7XXX_PHY
>         select MDIO_BCM_UNIMAC
>         select DIMLIB
> +       imply BROADCOM_PHY if ARCH_BCM2835

Which means support for the BROADCOM_PHY is always included
on ARCH_BCM2835, even if a different PHY is used?

>         help
>           This driver supports the built-in Ethernet MACs found in the
>           Broadcom BCM7xxx Set Top Box family chipset.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH net] net: broadcom: Imply BROADCOM_PHY for BCMGENET

[Florian Fainelli]

On 5/9/2020 12:38 AM, Geert Uytterhoeven wrote:
> Hi Florian,
> 
> Thanks for your patch!
> 
> On Sat, May 9, 2020 at 12:32 AM Florian Fainelli <f.fainelli@gmail.com> wrote:
>> The GENET controller on the Raspberry Pi 4 (2711) is typically
>> interfaced with an external Broadcom PHY via a RGMII electrical
>> interface. To make sure that delays are properly configured at the PHY
>> side, ensure that we get a chance to have the dedicated Broadcom PHY
>> driver (CONFIG_BROADCOM_PHY) enabled for this to happen.
> 
> I guess it can be interfaced to a different external PHY, too?

Yes, although this has not happened yet to the best of my knowledge.

> 
>> Fixes: 402482a6a78e ("net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB_CTRL when not needed")
>> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> 
>> --- a/drivers/net/ethernet/broadcom/Kconfig
>> +++ b/drivers/net/ethernet/broadcom/Kconfig
>> @@ -69,6 +69,7 @@ config BCMGENET
>>          select BCM7XXX_PHY
>>          select MDIO_BCM_UNIMAC
>>          select DIMLIB
>> +       imply BROADCOM_PHY if ARCH_BCM2835
> 
> Which means support for the BROADCOM_PHY is always included
> on ARCH_BCM2835, even if a different PHY is used?

It is included by default on  and can be deselected if needed, which is 
exactly what we want here, a sane default, but without the inflexibility 
of "select".

> 
>>          help
>>            This driver supports the built-in Ethernet MACs found in the
>>            Broadcom BCM7xxx Set Top Box family chipset.
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
> 

-- 
Florian

Re: [PATCH net] net: broadcom: Imply BROADCOM_PHY for BCMGENET

[Geert Uytterhoeven]

Hi Florian,

On Sat, May 9, 2020 at 7:12 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> On 5/9/2020 12:38 AM, Geert Uytterhoeven wrote:
> > On Sat, May 9, 2020 at 12:32 AM Florian Fainelli <f.fainelli@gmail.com> wrote:
> >> The GENET controller on the Raspberry Pi 4 (2711) is typically
> >> interfaced with an external Broadcom PHY via a RGMII electrical
> >> interface. To make sure that delays are properly configured at the PHY
> >> side, ensure that we get a chance to have the dedicated Broadcom PHY
> >> driver (CONFIG_BROADCOM_PHY) enabled for this to happen.
> >
> > I guess it can be interfaced to a different external PHY, too?
>
> Yes, although this has not happened yet to the best of my knowledge.
>
> >
> >> Fixes: 402482a6a78e ("net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB_CTRL when not needed")
> >> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> >> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> >
> >> --- a/drivers/net/ethernet/broadcom/Kconfig
> >> +++ b/drivers/net/ethernet/broadcom/Kconfig
> >> @@ -69,6 +69,7 @@ config BCMGENET
> >>          select BCM7XXX_PHY
> >>          select MDIO_BCM_UNIMAC
> >>          select DIMLIB
> >> +       imply BROADCOM_PHY if ARCH_BCM2835
> >
> > Which means support for the BROADCOM_PHY is always included
> > on ARCH_BCM2835, even if a different PHY is used?
>
> It is included by default on  and can be deselected if needed, which is
> exactly what we want here, a sane default, but without the inflexibility
> of "select".

I stand corrected: I can confirm the "imply" no longer selects the target
symbol, but merely changes the default.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH net] net: broadcom: Imply BROADCOM_PHY for BCMGENET

[Marek Szyprowski]

Hi Florian,

On 09.05.2020 00:32, Florian Fainelli wrote:
> The GENET controller on the Raspberry Pi 4 (2711) is typically
> interfaced with an external Broadcom PHY via a RGMII electrical
> interface. To make sure that delays are properly configured at the PHY
> side, ensure that we get a chance to have the dedicated Broadcom PHY
> driver (CONFIG_BROADCOM_PHY) enabled for this to happen.
>
> Fixes: 402482a6a78e ("net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB_CTRL when not needed")
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
> David,
>
> I would like Marek to indicate whether he is okay or not with this
> change. Thanks!

It is better. It fixes the default values for ARM 32bit 
bcm2835_defconfig and ARM 64bit defconfig, so you can add:

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

There is still an issue there. In case of ARM 64bit, when Genet driver 
is configured as a module, BROADCOM_PHY is also set to module. When I 
changed Genet to be built-in, BROADCOM_PHY stayed selected as module. 
This case doesn't work, as Genet driver is loaded much earlier than the 
rootfs/initrd/etc is available, thus broadcom phy driver is not loaded 
at all. It looks that some kind of deferred probe is missing there.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH net] net: broadcom: Imply BROADCOM_PHY for BCMGENET

[Florian Fainelli]

On 5/11/2020 12:21 AM, Marek Szyprowski wrote:
> Hi Florian,
> 
> On 09.05.2020 00:32, Florian Fainelli wrote:
>> The GENET controller on the Raspberry Pi 4 (2711) is typically
>> interfaced with an external Broadcom PHY via a RGMII electrical
>> interface. To make sure that delays are properly configured at the PHY
>> side, ensure that we get a chance to have the dedicated Broadcom PHY
>> driver (CONFIG_BROADCOM_PHY) enabled for this to happen.
>>
>> Fixes: 402482a6a78e ("net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB_CTRL when not needed")
>> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
>> ---
>> David,
>>
>> I would like Marek to indicate whether he is okay or not with this
>> change. Thanks!
> 
> It is better. It fixes the default values for ARM 32bit 
> bcm2835_defconfig and ARM 64bit defconfig, so you can add:
> 
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> 
> There is still an issue there. In case of ARM 64bit, when Genet driver 
> is configured as a module, BROADCOM_PHY is also set to module. When I 
> changed Genet to be built-in, BROADCOM_PHY stayed selected as module. 

OK.

> This case doesn't work, as Genet driver is loaded much earlier than the 
> rootfs/initrd/etc is available, thus broadcom phy driver is not loaded 
> at all. It looks that some kind of deferred probe is missing there.

In the absence of a specific PHY driver the Generic PHY driver gets used
instead. This is a valid situation as I described in my other email
because the boot loader/firmware could have left the PHY properly
configured with the expected RGMII delays and configuration such that
Linux does not need to be aware of anything. I suppose we could change
the GENET driver when running on the 2711 platform to reject the PHY
driver being "Generic PHY" on the premise that a specialized driver
should be used instead, but that seems a bit too restrictive IMHO.

Do you prefer a "select BROADCOM_PHY if ARCH_BCM2835" then?
-- 
Florian

Re: [PATCH net] net: broadcom: Imply BROADCOM_PHY for BCMGENET

[Marek Szyprowski]

Hi Florian,

On 11.05.2020 20:19, Florian Fainelli wrote:
> On 5/11/2020 12:21 AM, Marek Szyprowski wrote:
>> On 09.05.2020 00:32, Florian Fainelli wrote:
>>> The GENET controller on the Raspberry Pi 4 (2711) is typically
>>> interfaced with an external Broadcom PHY via a RGMII electrical
>>> interface. To make sure that delays are properly configured at the PHY
>>> side, ensure that we get a chance to have the dedicated Broadcom PHY
>>> driver (CONFIG_BROADCOM_PHY) enabled for this to happen.
>>>
>>> Fixes: 402482a6a78e ("net: bcmgenet: Clear ID_MODE_DIS in EXT_RGMII_OOB_CTRL when not needed")
>>> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
>>> ---
>>> David,
>>>
>>> I would like Marek to indicate whether he is okay or not with this
>>> change. Thanks!
>> It is better. It fixes the default values for ARM 32bit
>> bcm2835_defconfig and ARM 64bit defconfig, so you can add:
>>
>> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>
>> There is still an issue there. In case of ARM 64bit, when Genet driver
>> is configured as a module, BROADCOM_PHY is also set to module. When I
>> changed Genet to be built-in, BROADCOM_PHY stayed selected as module.
> OK.
>
>> This case doesn't work, as Genet driver is loaded much earlier than the
>> rootfs/initrd/etc is available, thus broadcom phy driver is not loaded
>> at all. It looks that some kind of deferred probe is missing there.
> In the absence of a specific PHY driver the Generic PHY driver gets used
> instead. This is a valid situation as I described in my other email
> because the boot loader/firmware could have left the PHY properly
> configured with the expected RGMII delays and configuration such that
> Linux does not need to be aware of anything. I suppose we could change
> the GENET driver when running on the 2711 platform to reject the PHY
> driver being "Generic PHY" on the premise that a specialized driver
> should be used instead, but that seems a bit too restrictive IMHO.
>
> Do you prefer a "select BROADCOM_PHY if ARCH_BCM2835" then?

Yes. It solves the issue after switching Genet to be built-in without 
the need to change the CONFIG_BROADCOM_PHY.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland