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

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Date: Fri, 21 Jun 2024 14:37:32 +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



> -----Original Message-----
> From: claudiu beznea <claudiu.beznea@...on.dev>
> Sent: Friday, June 21, 2024 3:31 PM
> To: Biju Das <biju.das.jz@...renesas.com>; Chris Brandt <Chris.Brandt@...esas.com>;
> andi.shyti@...nel.org; robh@...nel.org; krzk+dt@...nel.org; conor+dt@...nel.org;
> geert+renesas@...der.be; magnus.damm@...il.com; mturquette@...libre.com; sboyd@...nel.org;
> p.zabel@...gutronix.de; wsa+renesas@...g-engineering.com
> Cc: linux-renesas-soc@...r.kernel.org; linux-i2c@...r.kernel.org; devicetree@...r.kernel.org;
> linux-kernel@...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
> 
> 
> 
> On 21.06.2024 17:06, Biju Das wrote:
> > 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.
> 
> And I would add, as it is in this case: there are multiple instantiation of the RIIC in RZ/G3S SoC.
> RIIC 0 and 1 supports FMP, RIIC 2 and 3 does not.
> 
> For all RIICs (0, 1, 2, 3) we use the same compatible (as all are part of the same SoC). How to do
> the match b/w DT RIIC channel and driver with the solution you propose w/o hardcoding some RIIC
> channel data in the driver?

.info =0x3, so you know from the capability, for this soc, bus 0 and 1 supports FMP.

Cheers,
Biju


> 
> >
> > 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