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

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Message-ID: <871c563d-daa5-4be4-b114-9a8072e4edd0@tuxon.dev>
Date: Fri, 21 Jun 2024 17:30:39 +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 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?

> 
> 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