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

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Date: Sat, 29 Jun 2024 14:11:05 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Geert Uytterhoeven <geert@...ux-m68k.org>,
 "wsa+renesas@...g-engineering.com" <wsa+renesas@...g-engineering.com>,
 "andi.shyti@...nel.org" <andi.shyti@...nel.org>
Cc: Biju Das <biju.das.jz@...renesas.com>,
 Chris Brandt <Chris.Brandt@...esas.com>, "robh@...nel.org"
 <robh@...nel.org>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
 "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "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>,
 "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



On 28.06.2024 14:39, Geert Uytterhoeven wrote:
> On Fri, Jun 28, 2024 at 12:29 PM claudiu beznea
> <claudiu.beznea@...on.dev> wrote:
>> On 28.06.2024 12:13, Geert Uytterhoeven wrote:
>>> 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>
>>>>>> On 28.06.2024 10:55, Biju Das wrote:
>>>>>>>> -----Original Message-----
>>>>>>>> From: claudiu beznea <claudiu.beznea@...on.dev>
>>>>>>>> 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;
>>

FTR, the full context of this change is (from patch 09/12):

@@ -315,11 +319,13 @@ static int riic_init_hw(struct riic_dev *riic)
 	int total_ticks, cks, brl, brh;
 	struct i2c_timings *t = &riic->i2c_t;
 	struct device *dev = riic->adapter.dev.parent;
+	const struct riic_of_data *info = riic->info;

-	if (t->bus_freq_hz > I2C_MAX_FAST_MODE_FREQ) {
-		dev_err(dev,
-			"unsupported bus speed (%dHz). %d max\n",
-			t->bus_freq_hz, I2C_MAX_FAST_MODE_FREQ);
+	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;
 	}

Thank you,
Claudiu Beznea

>> 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).
> 
> Wolfram/Andi: what is your view on this?
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
>