Re: [PATCH v4 3/3] arm64: defconfig: Enable BCM2712 on-chip pin controller driver

[Andrea della Porta <andrea.porta@suse.com>]

Hi Florian,

On 10:19 Thu 28 Aug     , Florian Fainelli wrote:
> On 8/28/25 05:47, Andrea della Porta wrote:
> > Select the on-chip pin controller driver for BCM2712 SoC.
> > 
> > On RapsberryPi 5 devices it is primarily needed to operate the
> > bluetooth and WiFi devices, to configure the uSD interface
> > and the power button.
> > 
> > Signed-off-by: Andrea della Porta <andrea.porta@suse.com>
> > ---
> >   arch/arm64/configs/defconfig | 2 ++
> >   1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
> > index 58f87d09366c..d4c3853d885d 100644
> > --- a/arch/arm64/configs/defconfig
> > +++ b/arch/arm64/configs/defconfig
> > @@ -592,6 +592,8 @@ CONFIG_SPI_TEGRA114=m
> >   CONFIG_SPI_SPIDEV=m
> >   CONFIG_SPMI=y
> >   CONFIG_SPMI_MTK_PMIF=m
> > +CONFIG_PINCTRL_BRCMSTB=y
> > +CONFIG_PINCTRL_BCM2712=y
> 
> Do those need to be built-in or does it work good enough if you have them as
> loadable modules?

They do work reasonably well as modules too, but you need to add
them to initrd, the reason being that this patch [1] is referencing
the pinctrl driver from the SD card node so you need them early or
you won't be able to boot from SD.

Also, since many other nodes will reference the SoC pin controller,
I would expect some minor latency due to deferred probe, so keeping
them as built-in could bring some performance benefit.

A minor note: skimming through defconfig it seems that most pinctrl
drivers are built-ins, so I would stick to that too.

Many thanks,
Andrea


Links

1 - https://lore.kernel.org/all/5ceba8558e0007a9685f19b51d681d0ce79e7634.1756386531.git.andrea.porta@suse.com/
 
> -- 
> Florian