linux-kernel - Re: [PATCH v3 0/9] Add the Renesas USBF controller support

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Message-ID: <CAMuHMdU4YMmAtZE6XRgaLpqeq1Q6RPX4gE6og3QfY9T9Arw=6A@mail.gmail.com>
Date:   Thu, 8 Dec 2022 10:11:59 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Herve Codina <herve.codina@...tlin.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Magnus Damm <magnus.damm@...il.com>,
        Gareth Williams <gareth.williams.jx@...esas.com>,
        linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: Re: [PATCH v3 0/9] Add the Renesas USBF controller support

Hi Hervé,

On Thu, Dec 8, 2022 at 9:24 AM Herve Codina <herve.codina@...tlin.com> wrote:
> On Wed, 7 Dec 2022 16:19:42 -0600
> Rob Herring <robh+dt@...nel.org> wrote:
> > On Wed, Dec 7, 2022 at 10:24 AM Herve Codina <herve.codina@...tlin.com> wrote:
> > > This series add support for the Renesas USBF controller (USB Device
> > > Controller) available in the Renesas RZ/N1 SoC.
> > >
> > > Based on previous review:
> > >   https://lore.kernel.org/all/20221114111513.1436165-3-herve.codina@bootlin.com/
> > >
> > > A new strategy is proposed to handle the H2MODE bit from CFG_USB
> > > register compared to the previous versions on the series. As a
> > > reminder, H2MODE bit allows to configure the internal USB Port
> > > interface for two hosts or one host and one device.
> >
> > Is this case any different from all the phandle properties we have in
> > bindings that point to some misc registers somewhere else you need to
> > poke? If so, I'm not really a fan of duplicating the information.
>
> Our case is that there is a bit in a register that affect several
> devices. This bit must be set before the devices are started.
> If this bit is changed while affected devices are running, system
> hangs can occurs (datasheet).
>
> So, in order to do that we need the device in charge to set
> this bit (sysctrl) to set this bit before other devices (USBF
> and PCI bridge) were started.
>
> At sysctrl level, the bit is set during the probe() call.
> The property 'depends-on' aim is to ensure the probe() calls
> order between provider (sysctrl) and consumers (USBF and PCI
> bridge).

This order is already guaranteed (twice), through the clocks and
power-domains properties in the USB host and device nodes,
all pointing to sysctrl.

So IMHO none of this is needed.

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