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

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Herve Codina <herve.codina@bootlin.com>
Cc: Rob Herring <robh+dt@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Magnus Damm <magnus.damm@gmail.com>,
	Gareth Williams <gareth.williams.jx@renesas.com>,
	linux-renesas-soc@vger.kernel.org, linux-clk@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-usb@vger.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>
Subject: Re: [PATCH v3 0/9] Add the Renesas USBF controller support
Date: Thu, 8 Dec 2022 10:11:59 +0100	[thread overview]
Message-ID: <CAMuHMdU4YMmAtZE6XRgaLpqeq1Q6RPX4gE6og3QfY9T9Arw=6A@mail.gmail.com> (raw)
In-Reply-To: <20221208092439.6170cf5e@bootlin.com>

Hi Hervé,

On Thu, Dec 8, 2022 at 9:24 AM Herve Codina <herve.codina@bootlin.com> wrote:
> On Wed, 7 Dec 2022 16:19:42 -0600
> Rob Herring <robh+dt@kernel.org> wrote:
> > On Wed, Dec 7, 2022 at 10:24 AM Herve Codina <herve.codina@bootlin.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@linux-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