Date:   Wed, 06 Jul 2022 15:02:01 +0200
From:   Alexander Stein <alexander.stein@...tq-group.com>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Tony Lindgren <tony@...mide.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        iommu@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-gpio@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: Re: Re: Re: [PATCH v2 1/9] PM: domains: Delete usage of
 driver_deferred_probe_check_state()

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@...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@...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@...tq-group.com> wrote:
> > > > > > Hi,
> > > > > > 
> > > > > > Am Dienstag, 21. Juni 2022, 09:28:43 CEST schrieb Tony Lindgren:
> > > > > > > Hi,
> > > > > > > 
> > > > > > > * Saravana Kannan <saravanak@...gle.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@...a0000 {
> > > > >     
> > > > >         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@...a0000 !
> > > 
> > > 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@...us@...00000/timer@...a0000
> > > 
> > > 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

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.

> 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

View attachment "dmesg.short" of type "text/plain" (42237 bytes)

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