linux-kernel - RE: [PATCH 08/12] dt-bindings: i2c: renesas,riic: Document the R9A08G045 support

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Message-ID:
 <TY3PR01MB113468EF895A0EBED5DBD975D86C92@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Fri, 21 Jun 2024 14:06:51 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Claudiu.Beznea <claudiu.beznea@...on.dev>, Chris Brandt
	<Chris.Brandt@...esas.com>, "andi.shyti@...nel.org" <andi.shyti@...nel.org>,
	"robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
	<krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
	"geert+renesas@...der.be" <geert+renesas@...der.be>, "magnus.damm@...il.com"
	<magnus.damm@...il.com>, "mturquette@...libre.com" <mturquette@...libre.com>,
	"sboyd@...nel.org" <sboyd@...nel.org>, "p.zabel@...gutronix.de"
	<p.zabel@...gutronix.de>, "wsa+renesas@...g-engineering.com"
	<wsa+renesas@...g-engineering.com>
CC: "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>, Claudiu Beznea
	<claudiu.beznea.uj@...renesas.com>
Subject: RE: [PATCH 08/12] dt-bindings: i2c: renesas,riic: Document the
 R9A08G045 support

Hi Claudiu,

> -----Original Message-----
> From: claudiu beznea <claudiu.beznea@...on.dev>
> Sent: Friday, June 21, 2024 2:30 PM
> Subject: Re: [PATCH 08/12] dt-bindings: i2c: renesas,riic: Document the R9A08G045 support
> 
> 
> 
> On 21.06.2024 16:10, Biju Das wrote:
> >
> >
> >> -----Original Message-----
> >> From: claudiu beznea <claudiu.beznea@...on.dev>
> >> Sent: Friday, June 21, 2024 2:06 PM
> >  Subject: Re: [PATCH 08/12] dt-bindings: i2c: renesas,riic: Document
> > the R9A08G045 support
> >>
> >>
> >>
> >> On 21.06.2024 15:56, Biju Das wrote:
> >>>
> >>> Hi claudiu,
> >>>
> >>>> -----Original Message-----
> >>>> From: claudiu beznea <claudiu.beznea@...on.dev>
> >>>> Sent: Friday, June 21, 2024 1:55 PM
> >>>> Subject: Re: [PATCH 08/12] dt-bindings: i2c: renesas,riic: Document
> >>>> the R9A08G045 support
> >>>>
> >>>>
> >>>>
> >>>> On 21.06.2024 15:34, Biju Das wrote:
> >>>>> Hi Claudiu,
> >>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: Claudiu <claudiu.beznea@...on.dev>
> >>>>>> Sent: Friday, June 21, 2024 12:23 PM
> >>>>>> Subject: [PATCH 08/12] dt-bindings: i2c: renesas,riic: Document
> >>>>>> the
> >>>>>> R9A08G045 support
> >>>>>>
> >>>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >>>>>>
> >>>>>> Document the Renesas RZ/G3S (R9A08G045) RIIC IP. This is
> >>>>>> compatible with the version available on Renesas RZ/V2H
> >>>>>> (R9A09G075). Most of the IP variants that the RIIC driver is working with supports fast mode
> plus.
> >>>>>> However, it happens that on the same SoC to have IP instatiations
> >>>>>> that support fast mode plus as well as IP instantiation that
> >>>>>> doesn't support it. For this, introduced the renesas,riic-no-fast- mode-plus property.
> >>>>>>
> >>>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >>>>>> ---
> >>>>>>  Documentation/devicetree/bindings/i2c/renesas,riic.yaml | 8
> >>>>>> ++++++++
> >>>>>>  1 file changed, 8 insertions(+)
> >>>>>>
> >>>>>> diff --git
> >>>>>> a/Documentation/devicetree/bindings/i2c/renesas,riic.yaml
> >>>>>> b/Documentation/devicetree/bindings/i2c/renesas,riic.yaml
> >>>>>> index 91ecf17b7a81..c0964edbca69 100644
> >>>>>> --- a/Documentation/devicetree/bindings/i2c/renesas,riic.yaml
> >>>>>> +++ b/Documentation/devicetree/bindings/i2c/renesas,riic.yaml
> >>>>>> @@ -25,6 +25,10 @@ properties:
> >>>>>>                - renesas,riic-r9a07g054  # RZ/V2L
> >>>>>>            - const: renesas,riic-rz      # RZ/A or RZ/G2L
> >>>>>>
> >>>>>> +      - items:
> >>>>>> +          - const: renesas,riic-r9a08g045   # RZ/G3S
> >>>>>> +          - const: renesas,riic-r9a09g057
> >>>>>> +
> >>>>>>        - const: renesas,riic-r9a09g057   # RZ/V2H(P)
> >>>>>>
> >>>>>>    reg:
> >>>>>> @@ -66,6 +70,10 @@ properties:
> >>>>>>    resets:
> >>>>>>      maxItems: 1
> >>>>>>
> >>>>>> +  renesas,riic-no-fast-mode-plus:
> >>>>>> +    description: specifies if fast mode plus is not supported
> >>>>>> +    type: Boolean
> >>>>>
> >>>>> Can't this info, as part of device data?? Based on frequency and
> >>>>> device data is enough to derive this info??
> >>>>
> >>>> We can't rely completely on device data because on RZ/G3S we have 2
> >>>> RIIC channels that support fast mode plus and 2 that doesn't support it.
> >>>
> >>> Can't array of bits for this channels won't help??
> >>
> >> Can you give an example? I'm not sure I understand how you would
> >> prefer me to use the array of bits.
> >
> > struct riic_of_data {
> > 	u8 regs[RIIC_REG_END];
> > 	u16 fast_mode_info info; /* 1 means fast mode plus supported,
> > starting with channel 0*/ };
> >
> > .info = 0x3, means channel 0 and 1 has fast mode plus supported .info
> > = 0x0, none of the channel supported fast mode plus.
> 
> If I understand the proposal correctly, a match b/w struct riic_of_data::info bit + frequency and
> the nodes in device tree is still needed, right? As the RZ/G3S RIIC channels are using the same
> compatible.
> W/o a match how I cannot detect in the driver who is, e.g., channel 1 that supports FMP w/o
> hardcoding some RIIC channel data in the driver (e.g. RIIC channel address)?

bit array gives the capability info on various channels.

If someone define fast_mode_plus frequency in DT node and channel is not fast_mode_plus(from the capability info)
then you should return error.

Here you need to use SoC specific compatible as each SoC has different capabilities.

Cheers,
Biju


> 
> Also, for future SoCs that will suffer the same symptom but for different channels (and channels
> with different addresses) the driver will have to be adapted to match b/w the channel bit in struct
> riic_of_data::info and channel node from DT.
> 
> >
> > Cheers,
> > Biju