Re: [PATCH RESEND v5 1/2] dt-bindings: i2c: spacemit: add support for K1 SoC

From: Yixun Lan <dlan@gentoo.org>
To: Samuel Holland <samuel.holland@sifive.com>
Cc: Troy Mitchell <troymitchell988@gmail.com>,
	Andi Shyti <andi.shyti@kernel.org>, Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	linux-riscv@lists.infradead.org, linux-i2c@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	spacemit@lists.linux.dev,
	Conor Dooley <conor.dooley@microchip.com>
Subject: Re: [PATCH RESEND v5 1/2] dt-bindings: i2c: spacemit: add support for K1 SoC
Date: Wed, 5 Mar 2025 14:10:14 +0000	[thread overview]
Message-ID: <20250305141014-GYB63227@gentoo> (raw)
In-Reply-To: <eda41d6d-fa08-413b-8f3c-ce044e171615@sifive.com>

Hi Samuel:

On 22:01 Tue 04 Mar     , Samuel Holland wrote:
> On 2025-03-04 9:05 PM, Yixun Lan wrote:
> >>>> +        clocks = <&ccu 176>, <&ccu 90>;
> >>>> +        clock-names = "apb", "twsi";
> >>> 9.1.4.61 TWSI0 CLOCK RESET CONTROL REGISTER(APBC_TWSI0_CLK_RST)
> >>> https://developer.spacemit.com/documentation?token=LCrKwWDasiJuROkVNusc2pWTnEb#part594
> >>> from above docs, there are two clocks 
> >>> bit[1] - FNCLK, TWSI0 Functional Clock Enable/Disable
> >>> bit[0] - APBCLK, TWSI0 APB Bus Clock Enable/Disable
> >>>
> >>> I'd suggest to name it according to the functionality, thus 'func', 'bus'
> >>> clock, not its source.. which would make it more system wide consistent
> >>
> >> Also in that same register is:
> >>
> >> 2	RST	RW	0x1	TWSI0 Reset Generation
> >> This field resets both the APB and functional domain.
> >> - 0: No Reset
> >> - 1: Reset
> >>
> >> Which means you need a 'resets' property in the binding as well.
> >>
> > right, there is reset needed
> > 
> > I'd suggest to add it as an incremental patch later, when we
> > implement real reset driver, and also complete the calling reset
> > consumer API in i2c driver
> > 
> > but, let me know if this is not the right way to go
> 
> If you add the resets property later, that's a breaking change to the DT,
> because existing devicetrees will not have that property. So you would have to
> make the reset consumer in the driver optional, even if it's not really
> optional, to work with older DTs. So it is _possible_ to add incrementally, but
> not recommended because it adds "legacy" code that never really goes away.
> 
Ok, that's fair if we want to keep DT backward compatible..

> It's okay to define the binding as requiring the resets property now, even
> before the reset controller driver is merged. You just won't be able to add the
> I2C controller to the DTS until the reset controller binding is merged. But
> since the reset controller is the same IP block as the clock controller, its
> binding should be available soon anyway.
> 
yes, this should work, thanks
I think we will wait for reset driver

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