Hi Uwe,
On Tue, Sep 17, 2019 at 2:25 PM Uwe Kleine-König
<u.kleine-koenig@xxxxxxxxxxxxxx> wrote:
> On Tue, Sep 17, 2019 at 11:25:46AM +0000, Peter Rosin wrote:
> > On 2019-09-17 12:13, Uwe Kleine-König wrote:
> > > On Tue, Sep 17, 2019 at 11:40:25AM +0200, Geert Uytterhoeven wrote:
> > >> On Fri, Sep 13, 2019 at 11:58 PM Rob Herring <robh@xxxxxxxxxx> wrote:
> > >>> On Sat, 24 Aug 2019 15:28:46 +0200, =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= wrote:
> > >>>> Referencing device tree nodes from a property allows to pass arguments.
> > >>>> This is for example used for referencing gpios. This looks as follows:
> > >>>>
> > >>>> gpio_ctrl: gpio-controller {
> > >>>> #gpio-cells = <2>
> > >>>> ...
> > >>>> }
> > >>>>
> > >>>> someothernode {
> > >>>> gpios = <&gpio_ctrl 5 0 &gpio_ctrl 3 0>;
> > >>>> ...
> > >>>> }
> > >>>>
> > >>>> To know the number of arguments this must be either fixed, or the
> > >>>> referenced node is checked for a $cells_name (here: "#gpio-cells")
> > >>>> property and with this information the start of the second reference can
> > >>>> be determined.
> > >>>>
> > >>>> Currently regulators are referenced with no additional arguments. To
> > >>>> allow some optional arguments without having to change all referenced
> > >>>> nodes this change introduces a way to specify a default cell_count. So
> > >>>> when a phandle is parsed we check for the $cells_name property and use
> > >>>> it as before if present. If it is not present we fall back to
> > >>>> cells_count if non-negative and only fail if cells_count is smaller than
> > >>>> zero.
> > >>>>
> > >>>> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> > >>
> > >> This is now commit e42ee61017f58cd9 ("of: Let of_for_each_phandle fallback
> > >> to non-negative cell_count") in robh/for-next, which causes a lock-up when
> > >> booting a shmobile_defconfig kernel on r8a7791/koelsch:
> > >>
> > >> rcu: INFO: rcu_sched self-detected stall on CPU
> Oh yeah, you're right. I'm a bit disappointed that I didn't spot this
> myself :-|
>
> Untested patch to fix this problem:
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 2f25d2dfecfa..26f7a21d7187 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -1284,6 +1284,13 @@ int of_phandle_iterator_init(struct of_phandle_iterator *it,
> const __be32 *list;
> int size;
>
> + /*
> + * one of cell_count or cells_name must be provided to determine the
> + * argument length.
> + */
> + if (cell_count < 0 && !cells_name)
> + return -EINVAL;
> +
> memset(it, 0, sizeof(*it));
>
> list = of_get_property(np, list_name, &size);
> @@ -1765,6 +1772,18 @@ int of_count_phandle_with_args(const struct device_node *np, const char *list_na
> struct of_phandle_iterator it;
> int rc, cur_index = 0;
>
> + /* If cells_name is NULL we assume an cell_count of 0 */
a cell count
> + if (cells_name == NULL) {
> + const __be32 *list;
> + int size;
> +
> + list = of_get_property(np, list_name, &size);
> + if (!list)
> + return -ENOENT;
> +
> + return size / sizeof(*list);
> + }
> +
> rc = of_phandle_iterator_init(&it, np, list_name, cells_name, -1);
> if (rc)
> return rc;
Thanks, that fixes the boot for me!
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
