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

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Date: Fri, 21 Jun 2024 16:29:41 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Biju Das <biju.das.jz@...renesas.com>,
 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



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)?

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