[v1,2/2] of: Let of_for_each_phandle fallback to non-negative cell_count
diff mbox series

Message ID 20190824132846.8589-2-u.kleine-koenig@pengutronix.de
State In Next
Commit e42ee61017f58cd91cb9e30001450be3981e0e83
Headers show
Series
  • [v1,1/2] iommu: pass cell_count = -1 to of_for_each_phandle with cells_name
Related show

Commit Message

Uwe Kleine-König Aug. 24, 2019, 1:28 p.m. UTC
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@pengutronix.de>
---
 drivers/of/base.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

Comments

Rob Herring Sept. 2, 2019, 2:26 p.m. UTC | #1
On Sat, Aug 24, 2019 at 03:28:46PM +0200, Uwe Kleine-König 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@pengutronix.de>
> ---
>  drivers/of/base.c | 25 +++++++++++++++++--------
>  1 file changed, 17 insertions(+), 8 deletions(-)

Looks fine to me. I can apply with an ack from the iommu folks on patch 
1.

Rob
Rob Herring Sept. 13, 2019, 9:58 p.m. UTC | #2
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@pengutronix.de>
> ---
>  drivers/of/base.c | 25 +++++++++++++++++--------
>  1 file changed, 17 insertions(+), 8 deletions(-)
> 

Applied both patches, thanks.

Rob
Geert Uytterhoeven Sept. 17, 2019, 9:40 a.m. UTC | #3
Hi Rob, Uwe,

On Fri, Sep 13, 2019 at 11:58 PM Rob Herring <robh@kernel.org> 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@pengutronix.de>

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?

Gr{oetje,eeting}s,

                        Geert
Uwe Kleine-König Sept. 17, 2019, 10:13 a.m. UTC | #4
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@kernel.org> 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@pengutronix.de>
> 
> 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

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 2f25d2dfecfa..2425a6d26038 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1769,8 +1769,13 @@ int of_count_phandle_with_args(const struct device_node *np, const char *list_na
 	if (rc)
 		return rc;
 
-	while ((rc = of_phandle_iterator_next(&it)) == 0)
+	pr_err("%s: enter loop (np=%pOF, list_name=%s, cells_name=%s)\n",
+	       __func__, np, list_name, cells_name);
+	while ((rc = of_phandle_iterator_next(&it)) == 0) {
+		pr_err("%s: it.node = %pOF cur_index=%d\n", __func__, it.node, cur_index);
 		cur_index += 1;
+	}
+	pr_err("%s: exit loop\n", __func__);
 
 	if (rc != -ENOENT)
 		return rc;

Thanks
Uwe
Peter Rosin Sept. 17, 2019, 11:25 a.m. UTC | #5
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@kernel.org> 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@pengutronix.de>
>>
>> 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!!! */
		}

		...
	}

	...
}

Cheers,
Peter

Patch
diff mbox series

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 55e7f5bb0549..2f25d2dfecfa 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1335,11 +1335,20 @@  int of_phandle_iterator_next(struct of_phandle_iterator *it)
 
 			if (of_property_read_u32(it->node, it->cells_name,
 						 &count)) {
-				pr_err("%pOF: could not get %s for %pOF\n",
-				       it->parent,
-				       it->cells_name,
-				       it->node);
-				goto err;
+				/*
+				 * If both cell_count and cells_name is given,
+				 * fall back to cell_count in absence
+				 * of the cells_name property
+				 */
+				if (it->cell_count >= 0) {
+					count = it->cell_count;
+				} else {
+					pr_err("%pOF: could not get %s for %pOF\n",
+					       it->parent,
+					       it->cells_name,
+					       it->node);
+					goto err;
+				}
 			}
 		} else {
 			count = it->cell_count;
@@ -1505,7 +1514,7 @@  int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
 {
 	if (index < 0)
 		return -EINVAL;
-	return __of_parse_phandle_with_args(np, list_name, cells_name, 0,
+	return __of_parse_phandle_with_args(np, list_name, cells_name, -1,
 					    index, out_args);
 }
 EXPORT_SYMBOL(of_parse_phandle_with_args);
@@ -1588,7 +1597,7 @@  int of_parse_phandle_with_args_map(const struct device_node *np,
 	if (!pass_name)
 		goto free;
 
-	ret = __of_parse_phandle_with_args(np, list_name, cells_name, 0, index,
+	ret = __of_parse_phandle_with_args(np, list_name, cells_name, -1, index,
 					   out_args);
 	if (ret)
 		goto free;
@@ -1756,7 +1765,7 @@  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;
 
-	rc = of_phandle_iterator_init(&it, np, list_name, cells_name, 0);
+	rc = of_phandle_iterator_init(&it, np, list_name, cells_name, -1);
 	if (rc)
 		return rc;