Re: [PATCH 1/9] dt-bindings: pwm: marvell,pxa: add optional property resets

From: Yixun Lan <dlan@gentoo.org>
To: Alex Elder <elder@riscstar.com>
Cc: Guodong Xu <guodong@riscstar.com>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Conor Dooley <conor@kernel.org>,
	ukleinek@kernel.org, robh@kernel.org, krzk+dt@kernel.org,
	conor+dt@kernel.org, paul.walmsley@sifive.com,
	palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr,
	drew@pdp7.com, inochiama@gmail.com, geert+renesas@glider.be,
	heylenay@4d2.org, tglx@linutronix.de, hal.feng@starfivetech.com,
	unicorn_wang@outlook.com, duje.mihanovic@skole.hr,
	linux-pwm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	spacemit@lists.linux.dev
Subject: Re: [PATCH 1/9] dt-bindings: pwm: marvell,pxa: add optional property resets
Date: Tue, 15 Apr 2025 12:28:07 +0000	[thread overview]
Message-ID: <20250415122807-GYA30943@gentoo> (raw)
In-Reply-To: <0bbd2842-72bc-47a7-832a-fc8833163e32@riscstar.com>

Hi Alex,

On 07:11 Tue 15 Apr     , Alex Elder wrote:
> On 4/15/25 5:12 AM, Yixun Lan wrote:
> > Hi Philipp,
> > 
> > On 17:54 Tue 15 Apr     , Guodong Xu wrote:
> >> On Tue, Apr 15, 2025 at 4:53 PM Philipp Zabel <p.zabel@pengutronix.de> wrote:
> >>>
> >>> On Fr, 2025-04-11 at 17:44 +0100, Conor Dooley wrote:
> >>>> On Fri, Apr 11, 2025 at 09:14:15PM +0800, Guodong Xu wrote:
> >>>>> Add an optional resets property for the Marvell PWM PXA binding.
> >>>>>
> >>>>> Signed-off-by: Guodong Xu <guodong@riscstar.com>
> >>>>> ---
> >>>>>   Documentation/devicetree/bindings/pwm/marvell,pxa-pwm.yaml | 3 +++
> >>>>>   1 file changed, 3 insertions(+)
> >>>>>
> >>>>> diff --git a/Documentation/devicetree/bindings/pwm/marvell,pxa-pwm.yaml b/Documentation/devicetree/bindings/pwm/marvell,pxa-pwm.yaml
> >>>>> index 9ee1946dc2e1..9640d4b627c2 100644
> >>>>> --- a/Documentation/devicetree/bindings/pwm/marvell,pxa-pwm.yaml
> >>>>> +++ b/Documentation/devicetree/bindings/pwm/marvell,pxa-pwm.yaml
> >>>>> @@ -31,6 +31,9 @@ properties:
> >>>>>     clocks:
> >>>>>       maxItems: 1
> >>>>>
> >>>>> +  resets:
> >>>>> +    maxItems: 1
> >>>>
> >>>> Do any of the currently supported devices use a reset? If not, then add
> >>>> this in tandem with the new compatible and only allow it there please.
> >>>
> >>> Also, if spacemit,k1-pwm can not work without the reset being
> >>> deasserted, mark it as required.
> > 
> > If I inerpret correctly, only reset requires explicitly being de-asserted,
> > need to mark as required? that's being said, if reset comes out as de-asserted
> >   by default after power reset, then not necessary?
> > (in other cases, some device block is in asserted state by default)
> 
> We can often benefit from the state that the boot loader has left
> things in, but I think it's better not to assume it if possible.
right, I agree mostly

> I suppose it might not be required though.
> 
> Anyway, the reset line is available to use; why not require it?
> 
maybe there are cases that users don't want to issue a reset..
so, want to make it optional.. I can think one example that,
display controller is up and working from bootloader to linux,
reset it will got a flicker picture..

anyway, my question was trying to understand the policy of
writting DTS hehind..

> 
> > thanks
> >>>
> >>
> >> Thank you Philipp. spacemit,k1-pwm can not work without the reset.
> >> I will add that in the next version.
> >>
> >> -Guodong
> >>
> >>> The driver can still use reset_control_get_optional.
> >>>
> >>> regards
> >>> Philipp
> > 
> 

-- 
Yixun Lan (dlan)
Gentoo Linux Developer
GPG Key ID AABEFD55