linux-kernel - Re: [RESEND PATCH v1 03/13] dt-bindings: mfd: ti,tps6594: Add TI TPS65224 PMIC

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Message-ID: <20240216-chimp-endowment-e4c241e8e466@wendy>
Date: Fri, 16 Feb 2024 11:47:03 +0000
From: Conor Dooley <conor.dooley@...rochip.com>
To: Julien Panis <jpanis@...libre.com>
CC: Conor Dooley <conor@...nel.org>, Kevin Hilman <khilman@...nel.org>,
	Bhargav Raviprakash <bhargav.r@...s.com>, <arnd@...db.de>,
	<broonie@...nel.org>, <conor+dt@...nel.org>, <devicetree@...r.kernel.org>,
	<gregkh@...uxfoundation.org>, <kristo@...nel.org>,
	<krzysztof.kozlowski+dt@...aro.org>, <lee@...nel.org>, <lgirdwood@...il.com>,
	<linus.walleij@...aro.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<m.nirmaladevi@...s.com>, <nm@...com>, <robh+dt@...nel.org>,
	<vigneshr@...com>
Subject: Re: [RESEND PATCH v1 03/13] dt-bindings: mfd: ti,tps6594: Add TI
 TPS65224 PMIC

On Fri, Feb 16, 2024 at 10:08:03AM +0100, Julien Panis wrote:
> On 2/14/24 18:45, Conor Dooley wrote:
> > On Wed, Feb 14, 2024 at 09:26:13AM -0800, Kevin Hilman wrote:
> > > Conor Dooley <conor@...nel.org> writes:
> > > > On Wed, Feb 14, 2024 at 03:01:06PM +0530, Bhargav Raviprakash wrote:
> > > > > On Fri 2/9/2024 10:41 PM, Conor Dooley wrote:
> > > > > > On Thu, Feb 08, 2024 at 04:23:33PM +0530, Bhargav Raviprakash wrote:
> > > > > > > TPS65224 is a Power Management IC with 4 Buck regulators and 3 LDO
> > > > > > > regulators, it includes additional features like GPIOs, watchdog, ESMs
> > > > > > > (Error Signal Monitor), and PFSM (Pre-configurable Finite State Machine)
> > > > > > > managing the state of the device.
> > > > > > > TPS6594 and TPS65224 have significant functional overlap.
> > > > > > What does "significant functional overlap" mean? Does one implement a
> > > > > > compatible subset of the other? I assume the answer is no, given there
> > > > > > seems to be some core looking registers at different addresses.
> > > > > The intention behind “significant functional overlap” was meant to
> > > > > indicate a lot of the features between TPS6594 and TPS65224 overlap,
> > > > > while there are some features specific to TPS65224.
> > > > > There is compatibility between the PMIC register maps, I2C, PFSM,
> > > > > and other drivers even though there are some core registers at
> > > > > different addresses.
> > > > > 
> > > > > Would it be more appropriate to say the 2 devices are compatible and have
> > > > > sufficient feature overlap rather than significant functional overlap?
> > > > If core registers are at different addresses, then it is unlikely that
> > > > these devices are compatible.
> > > That's not necessarily true.  Hardware designers can sometimes be
> > > creative. :)
> > Hence "unlikely" in my mail :)
> 
> For tps6594 and tps65224, some core registers are at different adresses
> indeed, but the code is the same for both MFD I2C/SPI entry points. As an
> example, the way CRC is enabled is exactly the same, even if the bit that
> must be set belongs to different registers. tps65224 has more resources and
> it's as if HW designers had had to re-organize the way bits are distributed
> among the registers (due to a lack of space, so to speak).
> 
> That said, if we consider that these devices are not compatible, what does it
> imply concretely for the next version ? Does that mean that:
> 1) Only a new binding must be created, even if MFD drivers and most of child
> drivers will be re-used ? (then the binding would simply be duplicated, but
> the drivers would not)
> 2) A new binding and new MFD drivers must be created, even if most of child
> drivers will be re-used ? (then the binding and MFD drivers would simply be
> duplicated, but the child drivers would not)
> 3) A new binding and new drivers (MFD and child devices) must be created ?
> 4) Anything else ?

If they're not compatible the next version of this patch does not need
to change, so option 4 I guess.



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