Re: Re: Re: Re: [PATCH v2 1/9] PM: domains: Delete usage of driver_deferred_probe_check_state()

Saravana Kannan
2022-07-13T00:45:51Z

On Wed, Jul 6, 2022 at 6:02 AM Alexander Stein
<alexander.stein@ew.tq-group.com> wrote:
>

Thanks for testing all my patches and helping me debug this.

Btw, can you try to keep the subject the same please? Looks like
somewhere in your path [EXT] is added sometimes. lore.kernel.org keeps
the thread together, but my email client (gmail) gets confused.

> Am Dienstag, 5. Juli 2022, 03:24:33 CEST schrieb Saravana Kannan:
> > On Mon, Jul 4, 2022 at 12:07 AM Alexander Stein
> >
> > <alexander.stein@ew.tq-group.com> wrote:
> > > Am Freitag, 1. Juli 2022, 09:02:22 CEST schrieb Saravana Kannan:
> > > > On Thu, Jun 30, 2022 at 11:02 PM Alexander Stein
> > > >
> > > > <alexander.stein@ew.tq-group.com> wrote:
> > > > > Hi Saravana,
> > > > >
> > > > > Am Freitag, 1. Juli 2022, 02:37:14 CEST schrieb Saravana Kannan:
> > > > > > On Thu, Jun 23, 2022 at 5:08 AM Alexander Stein
> > > > > >
> > > > > > <alexander.stein@ew.tq-group.com> wrote:
> > > > > > > Hi,
> > > > > > >
> > > > > > > Am Dienstag, 21. Juni 2022, 09:28:43 CEST schrieb Tony Lindgren:
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > * Saravana Kannan <saravanak@google.com> [700101 02:00]:
> > > > > > > > > Now that fw_devlink=on by default and fw_devlink supports
> > > > > > > > > "power-domains" property, the execution will never get to the
> > > > > > > > > point
> > > > > > > > > where driver_deferred_probe_check_state() is called before the
> > > > > > > > > supplier
> > > > > > > > > has probed successfully or before deferred probe timeout has
> > > > > > > > > expired.
> > > > > > > > >
> > > > > > > > > So, delete the call and replace it with -ENODEV.
> > > > > > > >
> > > > > > > > Looks like this causes omaps to not boot in Linux next. With
> > > > > > > > this
> > > > > > > > simple-pm-bus fails to probe initially as the power-domain is
> > > > > > > > not
> > > > > > > > yet available. On platform_probe() genpd_get_from_provider()
> > > > > > > > returns
> > > > > > > > -ENOENT.
> > > > > > > >
> > > > > > > > Seems like other stuff is potentially broken too, any ideas on
> > > > > > > > how to fix this?
> > > > > > >
> > > > > > > I think I'm hit by this as well, although I do not get a lockup.
> > > > > > > In my case I'm using
> > > > > > > arch/arm64/boot/dts/freescale/imx8mq-tqma8mq-mba8mx.dts and
> > > > > > > probing of
> > > > > > > 38320000.blk-ctrl fails as the power-domain is not (yet) registed.
> > > > > >
> > > > > > Ok, took a look.
> > > > > >
> > > > > > The problem is that there are two drivers for the same device and
> > > > > > they
> > > > > > both initialize this device.
> > > > > >
> > > > > > gpc: gpc@303a0000 {
> > > > > >
> > > > > > compatible = "fsl,imx8mq-gpc";
> > > > > >
> > > > > > }
> > > > > >
> > > > > > $ git grep -l "fsl,imx7d-gpc" -- drivers/
> > > > > > drivers/irqchip/irq-imx-gpcv2.c
> > > > > > drivers/soc/imx/gpcv2.c
> > > > > >
> > > > > > IMHO, this is a bad/broken design.
> > > > > >
> > > > > > So what's happening is that fw_devlink will block the probe of
> > > > > > 38320000.blk-ctrl until 303a0000.gpc is initialized. And it stops
> > > > > > blocking the probe of 38320000.blk-ctrl as soon as the first driver
> > > > > > initializes the device. In this case, it's the irqchip driver.
> > > > > >
> > > > > > I'd recommend combining these drivers into one. Something like the
> > > > > > patch I'm attaching (sorry for the attachment, copy-paste is
> > > > > > mangling
> > > > > > the tabs). Can you give it a shot please?
> > > > >
> > > > > I tried this patch and it delayed the driver initialization (those of
> > > > > UART
> > > > > as
> > > >
> > > > > well BTW). Unfortunately the driver fails the same way:
> > > > Thanks for testing the patch!
> > > >
> > > > > > [ 1.125253] imx8m-blk-ctrl 38320000.blk-ctrl: error -ENODEV:
> > > > > > failed
> > > > > > to
> > > > >
> > > > > attach power domain "bus"
> > > > >
> > > > > More than that it even introduced some more errors:
> > > > > > [ 0.008160] irq: no irq domain found for gpc@303a0000 !
> > > >
> > > > So the idea behind my change was that as long as the irqchip isn't the
> > > > root of the irqdomain (might be using the terms incorrectly) like the
> > > > gic, you can make it a platform driver. And I was trying to hack up a
> > > > patch that's the equivalent of platform_irqchip_probe() (which just
> > > > ends up eventually calling the callback you use in IRQCHIP_DECLARE().
> > > > I probably made some mistake in the quick hack that I'm sure if
> > > > fixable.
> > > >
> > > > > > [ 0.013251] Failed to map interrupt for
> > > > > > /soc@0/bus@30400000/timer@306a0000
> > > >
> > > > However, this timer driver also uses TIMER_OF_DECLARE() which can't
> > > > handle failure to get the IRQ (because it's can't -EPROBE_DEFER). So,
> > > > this means, the timer driver inturn needs to be converted to a
> > > > platform driver if it's supposed to work with the IRQCHIP_DECLARE()
> > > > being converted to a platform driver.
> > > >
> > > > But that's a can of worms not worth opening. But then I remembered
> > > > this simpler workaround will work and it is pretty much a variant of
> > > > the workaround that's already in the gpc's irqchip driver to allow two
> > > > drivers to probe the same device (people really should stop doing
> > > > that).
> > > >
> > > > Can you drop my previous hack patch and try this instead please? I'm
> > > > 99% sure this will work.
> > > >
> > > > diff --git a/drivers/irqchip/irq-imx-gpcv2.c
> > > > b/drivers/irqchip/irq-imx-gpcv2.c index b9c22f764b4d..8a0e82067924
> > > > 100644
> > > > --- a/drivers/irqchip/irq-imx-gpcv2.c
> > > > +++ b/drivers/irqchip/irq-imx-gpcv2.c
> > > > @@ -283,6 +283,7 @@ static int __init imx_gpcv2_irqchip_init(struct
> > > > device_node *node,
> > > >
> > > > * later the GPC power domain driver will not be skipped.
> > > > */
> > > >
> > > > of_node_clear_flag(node, OF_POPULATED);
> > > >
> > > > + fwnode_dev_initialized(domain->fwnode, false);
> > > >
> > > > return 0;
> > > >
> > > > }
> > >
> > > Just to be sure here, I tried this patch on top of next-20220701 but
> > > unfortunately this doesn't fix the original problem either. The timer
> > > errors are gone though.
> >
> > To clarify, you had the timer issue only with my "combine drivers" patch,
> > right?
>
> That's correct.
>
> > > The probe of imx8m-blk-ctrl got slightly delayed (from 0.74 to 0.90s
> > > printk
> > > time) but results in the identical error message.
> >
> > My guess is that the probe attempt of blk-ctrl is delayed now till gpc
> > probes (because of the device links getting created with the
> > fwnode_dev_initialized() fix), but by the time gpc probe finishes, the
> > power domains aren't registered yet because of the additional level of
> > device addition and probing.
> >
> > Can you try the attached patch please?
>
> Sure, it needed some small fixes though. But the error still is present.
>
> > And if that doesn't fix the issues, then enable the debug logs in the
> > following functions please and share the logs from boot till the
> > failure? If you can enable CONFIG_PRINTK_CALLER, that'd help too.
> > device_link_add()
> > fwnode_link_add()
> > fw_devlink_relax_cycle()
>
> I switched fw_devlink_relax_cycle() for fw_devlink_relax_link() as the former
> has no debug output here.
>
> For the record I added the following line to my kernel command line:
> > dyndbg="func device_link_add +p; func fwnode_link_add +p; func
> fw_devlink_relax_link +p"
>
> I attached the dmesg until the probe error to this mail. But I noticed the
> following lines which seem interesting:
> > [ 1.466620][ T8] imx-pgc imx-pgc-domain.5: Linked as a consumer to
> > regulator.8
> > [ 1.466743][ T8] imx-pgc imx-pgc-domain.5: imx_pgc_domain_probe: Probe
> succeeded
> > [ 1.474733][ T8] imx-pgc imx-pgc-domain.6: Linked as a consumer to
> regulator.9
> > [ 1.474774][ T8] imx-pgc imx-pgc-domain.6: imx_pgc_domain_probe: Probe
> succeeded

I'm guessing this happens after the probe error.

Ok, I looked at the dmesg logs and this pretty much confirms my
thought on why the probe ordering wasn't maintained.

The power domains lack a compatible property, so the blk-ctrl is
linked as a consumer of the gpc instead:
[ 0.343905][ T1] blk-ctrl@38320000 Linked as a fwnode consumer
to gpc@303a0000
[ 0.343943][ T1] blk-ctrl@38320000 Linked as a fwnode consumer
to clock-controller@30380000
This ^^ is the device tree parsing figuring out the dependencies
between the DT nodes.

[ 0.368462][ T1] platform 38320000.blk-ctrl: Linked as a
consumer to 30380000.clock-controller
[ 0.368542][ T1] platform 38320000.blk-ctrl: Linked as a
consumer to 303a0000.gpc
This ^^ is converting the DT node dependencies into device links.

So, the only real options are:
1. Fix DT and add a compatible string to the DT nodes.
2. Move the initcall level of the regulator driver so the powerdomain
probe doesn't get deferred. Not ideal that we are playing initcall
chicken to handle the feature meant to remove the need for initcall
chicken. But I see these "device, but won't have a compatible
property" as exceptions and feel it's okay to have to play with
initcall levels to handle those.
3. Provide a helper function that driver that do this (creating
devices for child DT nodes without compatible property) can use to
move/copy their consumer device links to the child devices they add.
And then fix up the gpc driver so that it copies the gpc -- blk-ctrl
device link to the proper power domain.
4. I have another idea for how I could fix that at a driver core
level, but I'm not sure it'll work yet and its definitely not
something I want to try and get in for 5.19 -- too late for that IMHO.

Want to give (2) a shot so that I can still try to keep the cleanup
series that caused this problem (that's the long term goal) while I
give (3) and (4) a shot for 5.20?

> regulator.8 and regulator.9 is the power sequencer, attached on I2C. This also
> makes perfectly sense if you look at [1]ff. These power domains are supplied
> by specific power supply rails. Several, if not all, imx8mq boards have this
> kind of setting.

Yeah, makes sense in terms of what's going on.

-Saravana

>
> > Btw, part of the reason I'm trying to make sure we fix it the right
> > way is that when we try to enable async boot by default, we don't run
> > into issues.
>
> Sounds resonable.
>
> Best regards,
> Alexander
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/
> arch/arm64/boot/dts/freescale/imx8mq-tqma8mq.dtsi#n84