Re: [PATCH v2 1/2] clk: ti: mux: resolve parent clocks by DT index, not by name

Hi Mathieu,

On Wed, 19 Aug 2026 at 07:39, Mathieu Dubois-Briand
<[email protected]> wrote:
> On Tue Aug 18, 2026 at 6:02 PM CEST, Geert Uytterhoeven wrote:
> > On Mon, 27 Jul 2026 at 09:44, Mathieu Dubois-Briand
> > <[email protected]> wrote:
> >> Resolve parent clocks by their index into the device tree "clocks"
> >> property rather than matching names as strings. Name-based matching is
> >> fragile because a clock's "clock-output-names" value in its provider
> >> node can differ from the name used to reference it in a consumer node,
> >> and because names must be globally unique across all clock providers.
> >>
> >> On AM335x, this caused broken clock trees where some clocks failed to
> >> enable because their parents could not be found.
> >>
> >> Replace of_clk_parent_fill() with a clk_parent_data array that sets
> >> .index to the array position.
> >>
> >> Fixes: ec7aa25fa483 ("ARM: dts: Use clock-output-names for am3")
> >> Signed-off-by: Mathieu Dubois-Briand <[email protected]>
> >
> > Thanks for your patch, which is now commit 667f420c09f1417c ("clk: ti:
> > mux: resolve parent clocks by DT index, not by name") in clk/clk-next.
> >
> > This breaks booting BeagleBone Black for me: I don't get any output
> > on the serial console, even with "earlycon keep_bootcon".  When the
> > watchdog kicks in (or on kernel panic?), the system reboots.
>
> Sorry for that!
>
> It's a bit unexpected, as the beaglebone black was one of my test
> platforms and I didn't see any issue.
>
> > Reverting this commit fixes the issue.
> > After reverting, I added debug code to print all parents, and compared
> > them to the DTB, but didn't see any discrepancies.
> >
> > Your similar change to drivers/clk/ti/composite.c does not cause any
> > issues for me.
> >
> > Do you have a clue?
> > Thanks!
>
> Can you describe what bootloader and device tree you are using for your
> tests? Any specific configuration?
>
> On my side, I have:
> - BeagleBone Black Wireless A5
> - am335x-boneblack-wireless.dtb
> - U-boot 2025.10-ti-g6825d60bea17. Maybe I should try with u-boot master
>   branch.

BeagleBone Black Rev C3 (by Seeed Studio)
am335x-boneblack.dtb
Stock U-Boot SPL 2019.04-00002-g31a8ae0206 (May 13 2020 - 09:26:17 -0500)

I am using my own config.

With omap2plus_defconfig and multi_v7_defconfig, it does boot.  However,
this commit does have an impact on /sys/kernel/debug/clk/clk_summary:

--- summary-7.2.0-rc2-00106-g0d4d262c1664       2026-08-19
10:56:51.622275674 +0200
+++ summary-7.2.0-rc2-00107-g667f420c09f1       2026-08-19
10:58:13.929823890 +0200
@@ -77,10 +77,14 @@
 clk_summary:

deviceless                      no_connection_id
 clk_summary:                clkdiv32k_ck         0       1        0
     32786       0          0     50000      Y
deviceless                      of_clk_get_from_provider
 clk_summary:

deviceless                      no_connection_id
-clk_summary:                   clk-24mhz-clkctrl:0000:0 0       4
   0        32786       0          0     50000      N
   deviceless                      clkdiv32k_ick
+clk_summary:                   clk-24mhz-clkctrl:0000:0 0       5
   0        32786       0          0     50000      N
   deviceless                      clkdiv32k_ick
 clk_summary:

deviceless                      of_clk_get_from_provider
 clk_summary:

deviceless                      of_clk_get_from_provider
 clk_summary:

deviceless                      no_connection_id
+clk_summary:                      wdt1_fck       0       1        0
     32786       0          0     50000      Y
deviceless                      wdt1_fck
+clk_summary:

deviceless                      no_connection_id
+clk_summary:                         l4-wkup-clkctrl:00d4:0 0       1
       0        32786       0          0     50000      N
             44e35000.target-module          fck
+clk_summary:

  deviceless                      no_connection_id
 clk_summary:                      l4-rtc-clkctrl:0000:0 0       1
   0        32786       0          0     50000      N
      44e3e074.target-module          fck
 clk_summary:

deviceless                      no_connection_id
 clk_summary:                      l4ls-clkctrl:0074:18 0       2
  0        32786       0          0     50000      N
     4804c000.gpio                   dbclk
@@ -297,17 +301,13 @@
 clk_summary:       l4-cefuse-clkctrl:0020:0      0       0        0
     24000000    0          0     50000      N         deviceless
                no_connection_id
 clk_summary: virt_19200000_ck                    0       0        0
     19200000    0          0     50000      Y   deviceless
          of_clk_get_from_provider
 clk_summary:
                                                 deviceless
          no_connection_id
-clk_summary: clk_rc32k_ck                        0       2        0
     32000       0          0     50000      Y   deviceless
          of_clk_get_from_provider
+clk_summary: clk_rc32k_ck                        0       1        0
     32000       0          0     50000      Y   deviceless
          of_clk_get_from_provider
 clk_summary:
                                                 deviceless
          no_connection_id
 clk_summary:    gpio0_dbclk_mux_ck               0       1        0
     32000       0          0     50000      Y      deviceless
             no_connection_id
 clk_summary:       l4-wkup-clkctrl:0008:18       0       2        0
     32000       0          0     50000      N         44e07000.gpio
                dbclk
 clk_summary:

44e07000.target-module          dbclk
 clk_summary:
                                                       deviceless
                of_clk_get_from_provider
 clk_summary:
                                                       deviceless
                no_connection_id
-clk_summary:    wdt1_fck                         0       1        0
     32000       0          0     50000      Y      deviceless
             wdt1_fck
-clk_summary:
                                                    deviceless
             no_connection_id
-clk_summary:       l4-wkup-clkctrl:00d4:0        0       1        0
     32000       0          0     50000      N
44e35000.target-module          fck
-clk_summary:
                                                       deviceless
                no_connection_id
 clk_summary: clk_32768_ck                        1       1        0
     32768       0          0     50000      Y   deviceless
          of_clk_get_from_provider
 clk_summary:
                                                 deviceless
          no_connection_id
 clk_summary:    sysclkout_pre_ck                 1       1        0
     32768       0          0     50000      Y      deviceless
             no_connection_id

I.e. wdt1_fck changed its parent from clk_rc32k_ck to
clk-24mhz-clkctrl:0000:0, which is probably not intended?

However, that is not the cause of the crash.  My .config has
CONFIG_INIT_STACK_ALL_PATTERN enabled, so any uninitialized local
variables contain garbage.

> @@ -136,7 +136,7 @@ static struct clk *_register_mux(struct device_node *node, const char *name,
>         init.name = name;
>         init.ops = &ti_clk_mux_ops;
>         init.flags = flags;
> -       init.parent_names = parent_names;
> +       init.parent_data = parent_data;
>         init.num_parents = num_parents;
>
>         /* struct clk_mux assignments

Init is not fully initialized, hence init.parent_names contains garbage
(before, .parent_data contained garbage).
As clk_core_populate_parent_map() prioritizes .parent_names over
.parent_data, the uninitialized .parent_data didn't cause any harm before.

I will send a patch to fix this.  This seems to be a recurring issue:
lots of clk_init_data structures are not fully initialized...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

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