From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Auger Eric <eric.auger@redhat.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
Philipp Zabel <p.zabel@pengutronix.de>,
Alex Williamson <alex.williamson@redhat.com>,
KVM list <kvm@vger.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH/RFC v4 1/2] reset: Add support for dedicated reset controls
Date: Wed, 19 Sep 2018 15:16:02 +0200 [thread overview]
Message-ID: <CAMuHMdUFY8CMfb9P=8Tox31_dUzau-jB7YHgYo6jffQ4L7GBqA@mail.gmail.com> (raw)
In-Reply-To: <727f9a0b-79bb-dea9-1da7-12ef58e8081b@redhat.com>
Hi Eric,
On Wed, Sep 19, 2018 at 2:09 PM Auger Eric <eric.auger@redhat.com> wrote:
> On 9/17/18 6:39 PM, Geert Uytterhoeven wrote:
> > In some SoCs multiple hardware blocks may share a reset control.
> > The existing reset control API for shared resets will only assert such a
> > reset when the drivers for all hardware blocks agree.
> > The existing exclusive reset control API still allows to assert such a
> > reset, but that impacts all other hardware blocks sharing the reset.
> >
> > Sometimes a driver needs to reset a specific hardware block, and be 100%
> > sure it has no impact on other hardware blocks. This is e.g. the case
> > for virtualization with device pass-through, where the host wants to
> > reset any exported device before and after exporting it for use by the
> > guest, for isolation.
> >
> > Hence a new flag for dedicated resets is added to the internal methods,
> > with a new public reset_control_get_dedicated() method, to obtain an
> > exclusive handle to a reset that is dedicated to one specific hardware
> > block.
> >
> > This supports both DT-based and lookup-based reset controls.
> >
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ---
> > v4:
> > - New.
> >
> > Notes:
> > - Dedicated lookup-based reset controls were not tested,
> > - Several internal functions now take 3 boolean flags, and should
> > probably be converted to take a bitmask instead,
> > - I think __device_reset() should call __reset_control_get() with
> > dedicated=true. However, that will impact existing users,
>
> why should it?
device_reset{,_optional}() are supposed to reset the passed device.
If the reset is not dedicated, doing so will reset other devices, too.
> > --- a/drivers/reset/core.c
> > +++ b/drivers/reset/core.c
> > @@ -459,9 +459,38 @@ static void __reset_control_put_internal(struct reset_control *rstc)
> > kref_put(&rstc->refcnt, __reset_control_release);
> > }
> >
> > +static bool __of_reset_is_dedicated(const struct device_node *node,
> > + const struct of_phandle_args args)
> > +{
> > + struct of_phandle_args args2;
> > + struct device_node *node2;
> > + int index, ret;
> > +
> > + for_each_node_with_property(node2, "resets") {
> > + if (node == node2)
> > + continue;
> > +
> > + for (index = 0; ; index++) {
> > + ret = of_parse_phandle_with_args(node2, "resets",
> > + "#reset-cells", index,
> > + &args2);
> > + if (ret)
> > + break;
> > +
> > + if (args2.np == args.np &&
> > + args2.args_count == args.args_count &&
> > + !memcmp(args2.args, args.args,
> > + args.args_count * sizeof(args.args[0])))
> > + return false;
> You need to call of_node_put(args2.np) (see of_parse_phandle_with_args
> kernel doc)
Thanks, nice catch!
> Isn't it sufficient to check device_node handles are equal?
That would make it work with #reset-cells == 0 only.
If #reset-cells > 0, the reset line specifier includes extra arguments.
On the Renesas SoCs I'm using, there's a single reset controller, so
args.np is always the same. The actual reset line is specified by
args.args[0]. See the "resets" properties in e.g.
https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git/tree/arch/arm64/boot/dts/renesas/r8a7795.dtsi
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
next prev parent reply other threads:[~2018-09-19 13:16 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-17 16:39 [PATCH/RFC v4 0/2] vfio: platform: Add generic reset controller support Geert Uytterhoeven
2018-09-17 16:39 ` [PATCH/RFC v4 1/2] reset: Add support for dedicated reset controls Geert Uytterhoeven
2018-09-18 6:42 ` Geert Uytterhoeven
2018-09-19 12:09 ` Auger Eric
2018-09-19 13:16 ` Geert Uytterhoeven [this message]
2018-09-19 15:28 ` Auger Eric
2018-09-19 14:58 ` Philipp Zabel
2018-09-19 15:24 ` Geert Uytterhoeven
2018-09-20 9:27 ` Philipp Zabel
2018-09-20 9:37 ` Geert Uytterhoeven
2018-09-17 16:39 ` [PATCH/RFC v4 2/2] vfio: platform: Add generic reset controller support Geert Uytterhoeven
2018-09-19 12:36 ` Auger Eric
2018-09-19 12:54 ` Geert Uytterhoeven
2018-09-19 15:31 ` Auger Eric
2018-09-19 18:19 ` Alex Williamson
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