linux-kernel - Re: [PATCH v2 07/12] i2c: riic: Define individual arrays to describe the register offsets

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Date: Fri, 28 Jun 2024 13:28:58 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: 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>,
 "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 v2 07/12] i2c: riic: Define individual arrays to describe
 the register offsets

Hi, Geert,

On 28.06.2024 12:13, Geert Uytterhoeven wrote:
> Hi Claudiu,
> 
> On Fri, Jun 28, 2024 at 10:12 AM claudiu beznea
> <claudiu.beznea@...on.dev> wrote:
>> On 28.06.2024 11:09, Biju Das wrote:
>>>> -----Original Message-----
>>>> From: claudiu beznea <claudiu.beznea@...on.dev>
>>>> Sent: Friday, June 28, 2024 9:03 AM
>>>> Subject: Re: [PATCH v2 07/12] i2c: riic: Define individual arrays to describe the register offsets
>>>>
>>>>
>>>>
>>>> On 28.06.2024 10:55, Biju Das wrote:
>>>>> Hi Claudiu,
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: claudiu beznea <claudiu.beznea@...on.dev>
>>>>>> Sent: Friday, June 28, 2024 8:32 AM
>>>>>> Subject: Re: [PATCH v2 07/12] i2c: riic: Define individual arrays to
>>>>>> describe the register offsets
>>>>>>
>>>>>> Hi, Biju,
>>>>>>
>>>>>> On 28.06.2024 08:59, Biju Das wrote:
>>>>>>> Hi Claudiu,
>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: Claudiu <claudiu.beznea@...on.dev>
>>>>>>>> Sent: Tuesday, June 25, 2024 1:14 PM
>>>>>>>> Subject: [PATCH v2 07/12] i2c: riic: Define individual arrays to
>>>>>>>> describe the register offsets
>>>>>>>>
>>>>>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>>>>>
>>>>>>>> Define individual arrays to describe the register offsets. In this
>>>>>>>> way we can describe different IP variants that share the same
>>>>>>>> register offsets but have differences in other characteristics.
>>>>>>>> Commit prepares for the addition
>>>>>> of fast mode plus.
>>>>>>>>
>>>>>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>>>>> ---
>>>>>>>>
>>>>>>>> Changes in v2:
>>>>>>>> - none
>>>>>>>>
>>>>>>>>  drivers/i2c/busses/i2c-riic.c | 58
>>>>>>>> +++++++++++++++++++----------------
>>>>>>>>  1 file changed, 31 insertions(+), 27 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/i2c/busses/i2c-riic.c
>>>>>>>> b/drivers/i2c/busses/i2c-riic.c index
>>>>>>>> 9fe007609076..8ffbead95492 100644
>>>>>>>> --- a/drivers/i2c/busses/i2c-riic.c
>>>>>>>> +++ b/drivers/i2c/busses/i2c-riic.c
>>>>>>>> @@ -91,7 +91,7 @@ enum riic_reg_list {  };
>>>>>>>>
>>>>>>>>  struct riic_of_data {
>>>>>>>> -        u8 regs[RIIC_REG_END];
>>>>>>>> +        const u8 *regs;
>>>>>>>
>>>>>>>
>>>>>>> Since you are touching this part, can we drop struct and Use u8* as
>>>>>>> device_data instead?
>>>>>>
>>>>>> Patch 09/12 "i2c: riic: Add support for fast mode plus" adds a new member to struct
>>>> riic_of_data.
>>>>>> That new member is needed to differentiate b/w hardware versions
>>>>>> supporting fast mode plus based on compatible.
>>>>>
>>>>> Are we sure RZ/A does not support fast mode plus?
>>>>
>>>> From commit description of patch 09/12:
>>>>
>>>> Fast mode plus is available on most of the IP variants that RIIC driver is working with. The
>>>> exception is (according to HW manuals of the SoCs where this IP is available) the Renesas RZ/A1H.
>>>> For this, patch introduces the struct riic_of_data::fast_mode_plus.
>>>>
>>>> I checked the manuals of all the SoCs where this driver is used.
>>>>
>>>> I haven't checked the H/W manual?
>>>>
>>>> On the manual I've downloaded from Renesas web site the FMPE bit of RIICnFER is not available on
>>>> RZ/A1H.
>>>
>>> I just found RZ/A2M manual, it supports FMP and register layout looks similar to RZ/G2L.
>>
>> I introduced struct riic_of_data::fast_mode_plus because of RZ/A1H.
> 
> Do you need to check for that?
> 
> The ICFER_FMPE bit won't be set unless the user specifies the FM+
> clock-frequency.  Setting clock-frequency beyond Fast Mode on RZ/A1H
> would be very wrong.

I need it to avoid this scenario ^. In patch 09/12 there is this code:

+	if ((!info->fast_mode_plus && t->bus_freq_hz > I2C_MAX_FAST_MODE_FREQ) ||
+	    (info->fast_mode_plus && t->bus_freq_hz > I2C_MAX_FAST_MODE_PLUS_FREQ)) {
+		dev_err(dev, "unsupported bus speed (%dHz). %d max\n", t->bus_freq_hz,
+			info->fast_mode_plus ? I2C_MAX_FAST_MODE_PLUS_FREQ :
+			I2C_MAX_FAST_MODE_FREQ);
 		return -EINVAL;

to avoid giving the user the possibility to set FM+ freq on platforms not
supporting it.

Please let me know if I'm missing something (or wrongly understood your
statement).

Thank you,
Claudiu Beznea

> 
> Gr{oetje,eeting}s,
> 
>                         Geert
>