Re: [PATCH v1 2/2] of: Let of_for_each_phandle fallback to non-negative cell_count
From: Uwe Kleine-König
Date: Tue Sep 17 2019 - 08:25:50 EST
On Tue, Sep 17, 2019 at 11:25:46AM +0000, Peter Rosin wrote:
> On 2019-09-17 12:13, Uwe Kleine-König wrote:
> > Hello Geert,
> >
> > On Tue, Sep 17, 2019 at 11:40:25AM +0200, Geert Uytterhoeven wrote:
> >> Hi Rob, Uwe,
> >>
> >> 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
> >> rcu: 0-....: (2099 ticks this GP) idle=6fe/1/0x40000002
> >> softirq=29/29 fqs=1050
> >> (t=2100 jiffies g=-1131 q=0)
> >> NMI backtrace for cpu 0
> >> CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> >> 5.3.0-rc2-shmobile-00050-ge42ee61017f58cd9 #376
> >> Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
> >> [<c010f8ac>] (unwind_backtrace) from [<c010b620>] (show_stack+0x10/0x14)
> >> [<c010b620>] (show_stack) from [<c073d038>] (dump_stack+0x7c/0x9c)
> >> [<c073d038>] (dump_stack) from [<c0742e80>] (nmi_cpu_backtrace+0xa0/0xb8)
> >> [<c0742e80>] (nmi_cpu_backtrace) from [<c0742f1c>] (nmi_trigger_cpumask_backtrace+0x84/0x114)
> >> [<c0742f1c>] (nmi_trigger_cpumask_backtrace) from [<c017d684>] (rcu_dump_cpu_stacks+0xac/0xc8)
> >> [<c017d684>] (rcu_dump_cpu_stacks) from [<c017a598>] (rcu_sched_clock_irq+0x2ac/0x6b4)
> >> [<c017a598>] (rcu_sched_clock_irq) from [<c0183980>] (update_process_times+0x30/0x5c)
> >> [<c0183980>] (update_process_times) from [<c01941a8>] (tick_nohz_handler+0xcc/0x120)
> >> [<c01941a8>] (tick_nohz_handler) from [<c05b1d40>] (arch_timer_handler_virt+0x28/0x30)
> >> [<c05b1d40>] (arch_timer_handler_virt) from [<c016c9e0>] (handle_percpu_devid_irq+0xe8/0x21c)
> >> [<c016c9e0>] (handle_percpu_devid_irq) from [<c0167a8c>] (generic_handle_irq+0x18/0x28)
> >> [<c0167a8c>] (generic_handle_irq) from [<c0167b3c>] (__handle_domain_irq+0xa0/0xb4)
> >> [<c0167b3c>] (__handle_domain_irq) from [<c03673ec>] (gic_handle_irq+0x58/0x90)
> >> [<c03673ec>] (gic_handle_irq) from [<c0101a8c>] (__irq_svc+0x6c/0x90)
> >> Exception stack(0xeb08dd30 to 0xeb08dd78)
> >> dd20: c0cc7514 20000013 00000005 00003b27
> >> dd40: eb7c4020 c0cc750c 00000051 00000051 20000013 c0c66b08 eb1cdc00 00000018
> >> dd60: 00000000 eb08dd80 c05c1a38 c0756c00 20000013 ffffffff
> >> [<c0101a8c>] (__irq_svc) from [<c0756c00>] (_raw_spin_unlock_irqrestore+0x1c/0x20)
> >> [<c0756c00>] (_raw_spin_unlock_irqrestore) from [<c05c1a38>] (of_find_node_by_phandle+0xcc/0xf0)
> >> [<c05c1a38>] (of_find_node_by_phandle) from [<c05c1bb8>] (of_phandle_iterator_next+0x68/0x178)
> >> [<c05c1bb8>] (of_phandle_iterator_next) from [<c05c22bc>] (of_count_phandle_with_args+0x5c/0x7c)
> >> [<c05c22bc>] (of_count_phandle_with_args) from [<c053fc38>] (i2c_demux_pinctrl_probe+0x24/0x1fc)
> >> [<c053fc38>] (i2c_demux_pinctrl_probe) from [<c04463c4>] (platform_drv_probe+0x48/0x94)
> >> [<c04463c4>] (platform_drv_probe) from [<c0444a20>] (really_probe+0x1f0/0x2b8)
> >> [<c0444a20>] (really_probe) from [<c0444e68>] (driver_probe_device+0x140/0x158)
> >> [<c0444e68>] (driver_probe_device) from [<c0444ff0>] (device_driver_attach+0x44/0x5c)
> >> [<c0444ff0>] (device_driver_attach) from [<c04450b4>] (__driver_attach+0xac/0xb4)
> >> [<c04450b4>] (__driver_attach) from [<c0443178>] (bus_for_each_dev+0x64/0xa0)
> >> [<c0443178>] (bus_for_each_dev) from [<c04438a8>] (bus_add_driver+0x148/0x1a8)
> >> [<c04438a8>] (bus_add_driver) from [<c0445ad0>] (driver_register+0xac/0xf0)
> >> [<c0445ad0>] (driver_register) from [<c0b010b0>] (do_one_initcall+0xa8/0x1d4)
> >> [<c0b010b0>] (do_one_initcall) from [<c0b01448>] (kernel_init_freeable+0x26c/0x2c8)
> >> [<c0b01448>] (kernel_init_freeable) from [<c0751c70>] (kernel_init+0x8/0x10c)
> >> [<c0751c70>] (kernel_init) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
> >> Exception stack(0xeb08dfb0 to 0xeb08dff8)
> >> dfa0: 00000000 00000000 00000000 00000000
> >> dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> >> dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
> >>
> >> Presumably it loops forever, due to a conversion of -1 to unsigned
> >> somewhere?
> >
> > Hmm, I fail to see the culprit. i2c_demux_pinctrl_probe calls
> > of_count_phandle_with_args with cells_name=NULL. With that I don't see
> > how my patch changes anything as the only change is in an if
> > (it->cells_name) block that shouldn't be relevant in your case.
> >
> > Can you please verify that the loop in of_count_phandle_with_args is
> > indeed not terminating, e.g. with
>
> The below indicated else-branch was not touched by e42ee61017f58cd9,
> which ends up setting the count to -1 (aka 0xff...ff in this case).
> No?
>
> int of_phandle_iterator_next(struct of_phandle_iterator *it)
> {
>
> ...
>
> if (it->cells_name) {
>
> ...
>
> } else {
> count = it->cell_count; /* <---- SUSPECT!!! */
> }
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 */
+ 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;
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |