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

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Message-ID: <CAMuHMdUmiQjsKt93jM62V5YR_NdtUDXhcxFs+F+BCu3NTNsx8Q@mail.gmail.com>
Date: Fri, 28 Jun 2024 13:39:37 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: "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>, claudiu beznea <claudiu.beznea@...on.dev>, 
	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 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;
>
> 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

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds