Messages in this thread | | | Subject | Re: [PATCH 1/2] irqchip: irq-meson-gpio: make it possible to build as a module | From | Neil Armstrong <> | Date | Thu, 5 Aug 2021 08:31:06 +0200 |
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Hi Saravana,
On 04/08/2021 23:47, Saravana Kannan wrote: > On Wed, Aug 4, 2021 at 11:20 AM Saravana Kannan <saravanak@google.com> wrote: >> >> On Wed, Aug 4, 2021 at 1:50 AM Marc Zyngier <maz@kernel.org> wrote: >>> >>> On Wed, 04 Aug 2021 02:36:45 +0100, >>> Saravana Kannan <saravanak@google.com> wrote: >>> >>> Hi Saravana, >>> >>> Thanks for looking into this. >> >> You are welcome. I just don't want people to think fw_devlink is broken :) >> >>> >>> [...] >>> >>>>> Saravana, could you please have a look from a fw_devlink perspective? >>>> >>>> Sigh... I spent several hours looking at this and wrote up an analysis >>>> and then realized I might be looking at the wrong DT files. >>>> >>>> Marc, can you point me to the board file in upstream that corresponds >>>> to the platform in which you see this issue? I'm not asking for [1], >>>> but the actual final .dts (not .dtsi) file that corresponds to the >>>> platform/board/system. >>> >>> The platform I can reproduce this on is described in >>> arch/arm64/boot/dts/amlogic/meson-sm1-khadas-vim3l.dts. It is an >>> intricate maze of inclusion, node merge and other DT subtleties. I >>> suggest you look at the decompiled version to get a view of the >>> result. >> >> Thanks. After decompiling it, it looks something like (stripped a >> bunch of reg and address properties and added the labels back): >> >> eth_phy: mdio-multiplexer@4c000 { >> compatible = "amlogic,g12a-mdio-mux"; >> clocks = <0x02 0x13 0x1e 0x02 0xb1>; >> clock-names = "pclk\0clkin0\0clkin1"; >> mdio-parent-bus = <0x22>; >> >> ext_mdio: mdio@0 { >> reg = <0x00>; >> >> ethernet-phy@0 { >> max-speed = <0x3e8>; >> interrupt-parent = <0x23>; >> interrupts = <0x1a 0x08>; >> phandle = <0x16>; >> }; >> }; >> >> int_mdio: mdio@1 { >> ... >> } >> } >> >> And phandle 0x23 refers to the gpio_intc interrupt controller with the >> modular driver. >> >>>> Based on your error messages, it's failing for mdio@0 which >>>> corresponds to ext_mdio. But none of the board dts files in upstream >>>> have a compatible property for "ext_mdio". Which means fw_devlink >>>> _should_ propagate the gpio_intc IRQ dependency all the way up to >>>> eth_phy. >>>> >>>> Also, in the failing case, can you run: >>>> ls -ld supplier:* >>>> >>>> in the /sys/devices/....<something>/ folder that corresponds to the >>>> "eth_phy: mdio-multiplexer@4c000" DT node and tell me what it shows? >>> >>> Here you go: >>> >>> root@tiger-roach:~# find /sys/devices/ -name 'supplier*'|grep -i mdio | xargs ls -ld >>> lrwxrwxrwx 1 root root 0 Aug 4 09:47 /sys/devices/platform/soc/ff600000.bus/ff64c000.mdio-multiplexer/supplier:platform:ff63c000.system-controller:clock-controller -> ../../../../virtual/devlink/platform:ff63c000.system-controller:clock-controller--platform:ff64c000.mdio-multiplexer >> >> As we discussed over chat, this was taken after the mdio-multiplexer >> driver "successfully" probes this device. This will cause >> SYNC_STATE_ONLY device links created by fw_devlink to be deleted >> (because they are useless after a device probes). So, this doesn't >> show the info I was hoping to demonstrate. >> >> In any case, one can see that fw_devlink properly created the device >> link for the clocks dependency. So fw_devlink is parsing this node >> properly. But it doesn't create a similar probe order enforcing device >> link between the mdio-multiplexer and the gpio_intc because the >> dependency is only present in a grand child DT node (ethernet-phy@0 >> under ext_mdio). So fw_devlink is working as intended. >> >> I spent several hours squinting at the code/DT yesterday. Here's what >> is going on and causing the problem: >> >> The failing driver in this case is >> drivers/net/mdio/mdio-mux-meson-g12a.c. And the only DT node it's >> handling is what I pasted above in this email. In the failure case, >> the call flow is something like this: >> >> g12a_mdio_mux_probe() >> -> mdio_mux_init() >> -> of_mdiobus_register(ext_mdio DT node) >> -> of_mdiobus_register_phy(ext_mdio DT node) >> -> several calls deep fwnode_mdiobus_phy_device_register(ethernet_phy DT node) >> -> Tried to get the IRQ listed in ethernet_phy and fails with >> -EPROBE_DEFER because the IRQ driver isn't loaded yet. >> >> The error is propagated correctly all the way up to of_mdiobus_register(), but >> mdio_mux_init() ignores the -EPROBE_DEFER from of_mdiobus_register() and just >> continues on with the rest of the stuff and returns success as long as >> one of the child nodes (in this case int_mdio) succeeds. >> >> Since the probe returns 0 without really succeeding, networking stuff >> just fails badly after this. So, IMO, the real problem is with >> mdio_mux_init() not propagating up the -EPROBE_DEFER. I gave Marc a >> quick hack (pasted at the end of this email) to test my theory and he >> confirmed that it fixes the issue (a few deferred probes later, things >> work properly). >> >> Andrew, I don't see any good reason for mdio_mux_init() not >> propagating the errors up correctly (at least for EPROBE_DEFER). I'll >> send a patch to fix this. Please let me know if there's a reason it >> has to stay as-is. > > I sent out the proper fix as a series: > https://lore.kernel.org/lkml/20210804214333.927985-1-saravanak@google.com/T/#t
Thanks a lot for digging here and providing the appropriate fixes !
Neil
> > Marc, can you give it a shot please? > > -Saravana > >> >> -Saravana >> >> index 110e4ee85785..d973a267151f 100644 >> --- a/drivers/net/mdio/mdio-mux.c >> +++ b/drivers/net/mdio/mdio-mux.c >> @@ -170,6 +170,9 @@ int mdio_mux_init(struct device *dev, >> child_bus_node); >> mdiobus_free(cb->mii_bus); >> devm_kfree(dev, cb); >> + /* Not a final fix. I think it can cause UAF issues. */ >> + mdio_mux_uninit(pb); >> + return r; >> } else { >> cb->next = pb->children; >> pb->children = cb;
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