linux-kernel - Re: [PATCH 2/2] pinctrl: spacemit: support I/O power domain configuration

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Message-ID: <B479B24A35F8D731+aUpl0JdKOziIH14S@kernel.org>
Date: Tue, 23 Dec 2025 17:50:08 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Inochi Amaoto <inochiama@...il.com>,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Yixun Lan <dlan@...too.org>,
	Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	Linus Walleij <linusw@...nel.org>
Cc: devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org,
	spacemit@...ts.linux.dev, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org
Subject: Re: [PATCH 2/2] pinctrl: spacemit: support I/O power domain
 configuration

On Tue, Dec 23, 2025 at 05:42:26PM +0800, Inochi Amaoto wrote:
> On Tue, Dec 23, 2025 at 05:11:12PM +0800, Troy Mitchell wrote:
> > IO domain power control registers are used to configure the operating
> > voltage of dual-voltage GPIO banks. By default, these registers are
> > configured for 3.3V operation. As a result, even when a GPIO bank is
> > externally supplied with 1.8V, the internal logic continues to
> > operate in the 3.3V domain, which may lead to functional failures.
> > 
> > This patch adds support for programming the IO domain power control
> > registers, allowing dual-voltage GPIO banks to be explicitly configured
> > for 1.8V operation when required.
> > 
> > Care must be taken when configuring these registers. If a GPIO bank is
> > externally supplied with 3.3V while the corresponding IO power domain
> > is configured for 1.8V, external current injection (back-powering)
> > may occur, potentially causing damage to the GPIO pin.
> > 
> > Due to these hardware constraints and safety considerations, the IO
> > domain power control registers are implemented as secure registers.
> > Access to these registers requires unlocking via the AIB Secure Access
> > Register (ASAR) in the APBC block before a single read or write
> > operation can be performed.
> > 
> > Signed-off-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
> > ---
> >  arch/riscv/boot/dts/spacemit/k1.dtsi  |   4 +-
> >  drivers/pinctrl/spacemit/pinctrl-k1.c | 131 +++++++++++++++++++++++++++++++++-
> >  2 files changed, 131 insertions(+), 4 deletions(-)
> > 
> 
> > diff --git a/arch/riscv/boot/dts/spacemit/k1.dtsi b/arch/riscv/boot/dts/spacemit/k1.dtsi
> > index 7818ca4979b6a7755722919a5958512aa11950ab..23ecb19624f227f3c39de35bf3078379f7a2490e 100644
> > --- a/arch/riscv/boot/dts/spacemit/k1.dtsi
> > +++ b/arch/riscv/boot/dts/spacemit/k1.dtsi
> > @@ -565,10 +565,12 @@ i2c8: i2c@...1d800 {
> >  
> >  		pinctrl: pinctrl@...1e000 {
> >  			compatible = "spacemit,k1-pinctrl";
> > -			reg = <0x0 0xd401e000 0x0 0x400>;
> > +			reg = <0x0 0xd401e000 0x0 0x400>,
> > +			      <0x0 0xd401e800 0x0 0x34>;
> >  			clocks = <&syscon_apbc CLK_AIB>,
> >  				 <&syscon_apbc CLK_AIB_BUS>;
> >  			clock-names = "func", "bus";
> > +			spacemit,apbc = <&syscon_apbc 0x50>;
> >  		};
> 
> If you insist on a new reg field, you should change the binding as well.
Yes, I forgot to modify the binding.

> This change breaks binding, can we use something like <0x0 0xd401e000 0x0 0x1000>?
I'll double check this. Thanks!

                            - Troy
> 
> Regards,
> Inochi
>