RE: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API

[Biju Das <biju.das.jz@bp.renesas.com>]

Hi Laurent,

Thanks for the feedback.

> Subject: Re: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API
> 
> On Mon, Jun 12, 2023 at 09:53:02AM +0000, Biju Das wrote:
> > Hi All,
> >
> > How do we proceed here between [1] and [2]?
> >
> > DT-Maintainers suggestion:
> > [1]
> > raa215300: pmic@12 {
> > 	compatible = "renesas,raa215300";
> > 	reg = <0x12>, <0x6f>;
> > 	reg-names = "main", "rtc";
> >
> > 	clocks = <&x2>;
> > 	clock-names = "xin";
> > 	/* Add Optional shared IRQ resource and share it to child and handle
> > it both in parent and child */ };
> >
> > Laurent/Wolfram suggestion to split it into two nodes and get rid of
> this patch:
> > [2]
> > 	raa215300: pmic @12 {
> > 		compatible = "renesas,raa215300";
> > 		reg = <0x12>;
> >
> > 		/* Add Optional shared IRQ */
> > 		renesas,raa215300-rtc = <&rtc_raa215300>; /* Parse the handle
> and Enable RTC , if present.*/
> > 	};
> >
> > 	rtc_raa215300: rtc@6f {
> > 		compatible = "renesas,raa215300-isl1208";
> 
> Make this
> 
>  		compatible = "renesas,raa215300-isl1208", "isil,isl1208";
> 
> Btw, it would be nice to convert
> Documentation/devicetree/bindings/rtc/isil,isl1208.txt to YAML.

It is already posted see [1] and [2]
[1]
https://patchwork.kernel.org/project/linux-renesas-soc/patch/20230602142426.438375-6-biju.das.jz@bp.renesas.com/

[2]
https://patchwork.kernel.org/project/linux-renesas-soc/patch/20230602142426.438375-7-biju.das.jz@bp.renesas.com/

> 
> > 		reg = <0x6f>;
> >
> > 		/* Add Optional shared IRQ */
> > 		clocks = <&x2>;
> > 		clock-names = "xin";
> > 		renesas,raa215300-pmic = <&pmic>; /* Parse the handle to get
> PMIC
> > version to check Oscillator bit is inverted or not */
> 
> This isn't nice. I would instead add a renesas,invert-xtoscb boolean
> property. If you don't want different DT sources for different revisions
> of the PMIC,

I need to support all PMIC versions with same image, as PMIC is just a component on the
SoM module. So SoM's have different PMIC versions.

> one option is to perform the auto-detection in the boot
> loader and update the DT dynamically there.

Yes, this is an option. Bootloader updates "renesas,invert-xtoscb" property based
on PMIC version.

Not sure, From binding perspective, Documenting "renesas,invert-xtoscb" is OK for
the relevant maintainers??

Cheers,
Biju


> 
> > 	};
> 
> 
> 
> > > -----Original Message-----
> > > From: Biju Das
> > > Sent: Thursday, June 8, 2023 1:57 PM
> > > To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > Cc: Wolfram Sang <wsa@kernel.org>; Geert Uytterhoeven <geert@linux-
> > > m68k.org>; Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>;
> > > Rob Herring <robh+dt@kernel.org>; Andrzej Hajda
> > > <andrzej.hajda@intel.com>; Neil Armstrong
> > > <neil.armstrong@linaro.org>; Robert Foss <rfoss@kernel.org>; David
> > > Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kieran
> > > Bingham <kieran.bingham@ideasonboard.com>;
> > > Mauro Carvalho Chehab <mchehab@kernel.org>; Hans Verkuil <hverkuil-
> > > cisco@xs4all.nl>; Alessandro Zummo <a.zummo@towertech.it>; Alexandre
> > > Belloni <alexandre.belloni@bootlin.com>; Jonas Karlman
> > > <jonas@kwiboo.se>; Jernej Skrabec <jernej.skrabec@gmail.com>; Uwe
> > > Kleine-König <u.kleine- koenig@pengutronix.de>; Corey Minyard
> > > <cminyard@mvista.com>; Marek Behún <kabel@kernel.org>; Jiasheng
> > > Jiang <jiasheng@iscas.ac.cn>; Antonio Borneo
> > > <antonio.borneo@foss.st.com>; Abhinav Kumar
> > > <quic_abhinavk@quicinc.com>; Ahmad Fatoum <a.fatoum@pengutronix.de>;
> > > dri-devel@lists.freedesktop.org; linux-i2c@vger.kernel.org;
> > > linux-media@vger.kernel.org; Geert Uytterhoeven
> > > <geert+renesas@glider.be>; Fabrizio Castro
> > > <fabrizio.castro.jz@renesas.com>; linux-renesas-soc@vger.kernel.org;
> > > Mark Brown <broonie@kernel.org>
> > > Subject: RE: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device
> > > API
> > >
> > > Hi Laurent,
> > >
> > > Thanks for the feedback.
> > >
> > > > Subject: Re: [PATCH v5 01/11] i2c: Enhance
> > > > i2c_new_ancillary_device API
> > > >
> > > > Hi Biju,
> > > >
> > > > On Thu, Jun 08, 2023 at 11:00:19AM +0000, Biju Das wrote:
> > > > > > Subject: Re: [PATCH v5 01/11] i2c: Enhance
> > > > > > i2c_new_ancillary_device API On Thu, Jun 08, 2023 at
> 06:41:35AM+0000, Biju Das wrote:
> > > > > > > > Subject: RE: [PATCH v5 01/11] i2c: Enhance
> > > > > > > > i2c_new_ancillary_device API
> > > > > > > > > Subject: Re: [PATCH v5 01/11] i2c: Enhance
> > > > > > > > > i2c_new_ancillary_device API
> > > > > > > > >
> > > > > > > > > Hi all,
> > > > > > > > >
> > > > > > > > > sorry for not being able to chime in earlier.
> > > > > > > > >
> > > > > > > > > > In Biju's particular use case, the i2c device responds
> > > > > > > > > > to two addresses, which is the standard i2c ancillary
> use case.
> > > > > > > > > > However, what's special
> > > > > > > > >
> > > > > > > > > Not quite. ancillary is used when a *driver* needs to
> > > > > > > > > take care of two addresses. We already have devices
> > > > > > > > > bundling two features into the same chip. I recall at
> > > > > > > > > least RTC + EEPROM somewhere. And so far, we have been
> > > > > > > > > handling this by creating two nodes in DT and have proper
> binding docs.
> > > > > > > > > I think this is cleaner. First, you can see in DT
> > > > > > > > > already what the compound device really consists of. In
> > > > > > > > > this case, which RTC and RTC driver is exactly needed.
> > > > > > > > > Second, the code added here adds complexity to the I2C
> > > > > > > > > core with another layer of inderection for dummy devices.
> > > > > > > >
> > > > > > > > FYI, please see [1] and [2]
> > > > > > > >
> > > > > > > > As per DT maintainers, most of PMICs are described with
> > > > > > > > one node, even though RTC is on separate address.
> > > > > > > > According to them the DT schema allows multiple addresses
> for children.
> > > > > > > > But currently we lacks implementation for that. The
> > > > > > > > enhancement to this API allows that.
> > > > > > > >
> > > > > > > > > > As some resources are shared (knowledge about the
> > > > > > > > > > clocks), splitting this in two distinct devices in DT
> > > > > > > > > > (which is what Biju's initial patch series did) would
> > > > > > > > > > need phandles to link both nodes together.
> > > > > > > > > >
> > > > > > > > > > Do you have a better idea how to represent this?
> > > > > > > > >
> > > > > > > > > Not sure if I understood this chip correctly, but maybe:
> > > > > > > > > The PMIC driver exposes a clock gate which can be
> > > > > > > > > consumed by the RTC driver?
> > > > > > >
> > > > > > > Let me give me some details of this PMIC chip.
> > > > > > >
> > > > > > > PMIC device has 2 addresses "0x12:- PMIC" , "0x6f"- rtc.
> > > > > > >
> > > > > > > It has XIN, XOUT, INT# pins and a register for firmware
> revisions.
> > > > > >
> > > > > > Is the firmware revision register accessed through address
> > > > > > 0x12
> > > > > > (PMIC) or 0x6f (RTC) ?
> > > > >
> > > > > 0x12(PMIC).
> > > > >
> > > > > > > Based on the system design,
> > > > > > >
> > > > > > > If XIN and XOUT is connected to external crystal, Internal
> > > > > > > oscillator is enabled for RTC. In this case we need to set
> > > > > > > the oscillator bit to "0".
> > > > > > >
> > > > > > > If XIN is connected to external clock source, Internal
> > > > > > > oscillator is disabled for RTC. In this case we need to set
> > > > > > > the oscillator bit to "1".
> > > > > >
> > > > > > Same here, which address is the oscillator bit accessed through
> ?
> > > > >
> > > > > RTC (0x6F)--> to set oscillator bit.
> > > >
> > > > And does the PMIC part depend on the oscillator bit being set
> > > > correctly, or is that used for the RTC only ?
> > >
> > > PMIC part does not. It is used only in RTC.
> > >
> > > Based on PMIC revision, we need to set the oscillator bit in RTC
> > > block for PMIC rev a0 and rest of the PMIC chips.
> > >
> > > On PMIC rev0, oscillator bit is inverted.
> > >
> > > > > > > If XIN and XOUT not connected RTC operation not possible.
> > > > > > >
> > > > > > > IRQ# (optional) functionality is shared between PMIC and RTC.
> > > > > > > (PMIC fault for various bucks/LDOs/WDT/OTP/NVM and alarm
> condition).
> > > > > >
> > > > > > IRQs can be shared between multiple devices so this shouldn't
> > > > > > be a problem.
> > > > >
> > > > > OK. How do we represent this IRQ in DT?
> > > >
> > > > You can simply reference the same IRQ from the interrupts property
> > > > of different DT nodes.
> > > >
> > > > > > > The board, I have doesn't populate IRQ# pin. If needed some
> > > > > > > customers can populate IRQ# pin and use it for PMIC fault
> > > > > > > and RTC alarm.
> > > > > > >
> > > > > > > Also, currently my board has PMIC rev a0 where oscillator
> > > > > > > bit is inverted and internal oscillator is enabled (ie: XIN
> > > > > > > and XOUT is connected to external crystal)
> 
> --
> Regards,
> 
> Laurent Pinchart