Re: Slow booting on x15

From: Saravana Kannan <saravanak@google.com>
To: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Tony Lindgren <tony@atomide.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Peter Ujfalusi <peter.ujfalusi@ti.com>,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	Linux-OMAP <linux-omap@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Geert Uytterhoeven <geert+renesas@glider.be>
Subject: Re: Slow booting on x15
Date: Thu, 1 Oct 2020 15:30:39 -0700	[thread overview]
Message-ID: <CAGETcx_gCJuNqhBo+a4f0YHeUQJm+WitREw=hvu_5VBMZENCuw@mail.gmail.com> (raw)
In-Reply-To: <CAGETcx8DFDRwh7pt6SofELPAFHqvP5YgomdBB=o+SuhbUXs_7A@mail.gmail.com>

On Thu, Oct 1, 2020 at 3:22 PM Saravana Kannan <saravanak@google.com> wrote:
>
> On Thu, Oct 1, 2020 at 12:43 PM Grygorii Strashko
> <grygorii.strashko@ti.com> wrote:
> >
> >
> >
> > On 01/10/2020 21:24, Saravana Kannan wrote:
> > > On Thu, Oct 1, 2020 at 5:56 AM Grygorii Strashko
> > > <grygorii.strashko@ti.com> wrote:
> > >>
> > >>
> > >>
> > >> On 01/10/2020 11:22, Laurent Pinchart wrote:
> > >>> Hi Tony,
> > >>>
> > >>> On Thu, Oct 01, 2020 at 11:17:48AM +0300, Tony Lindgren wrote:
> > >>>> * Tony Lindgren <tony@atomide.com> [201001 07:53]:
> > >>>>> * Peter Ujfalusi <peter.ujfalusi@ti.com> [200930 12:41]:
> > >>>>>> Fwiw on my beagle x15
> > >>>>>>
> > >>>>>> v5.8
> > >>>>>> [    9.908787] Run /sbin/init as init process
> > >>>>>>
> > >>>>>> v5.9-rc7
> > >>>>>> [   15.085373] Run /sbin/init as init process
> > >>>>>>
> > >>>>>>
> > >>>>>> It appears to be 'fixed' in next-20200928: the board does not even boot.
> > >>>>>
> > >>>>> Yeah so it seems :(
> > >>>>>
> > >>>>>> next-20200928 on omap5
> > >>>>>> [    9.936806] Run /sbin/init as init process
> > >>>>>>
> > >>>>>>
> > >>>>>> -rc7 spends most of it's time:
> > >>>>>> [    7.635530] Micrel KSZ9031 Gigabit PHY 48485000.mdio:01: attached PHY driver [Micrel KSZ9031 Gigabit PHY] (mii_bus:phy_addr=48485000.mdio:01, irq=POLL)
> > >>>>>> [   14.956671] cpsw 48484000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
> > >>>>>> [   15.005211] IP-Config: Complete:
> > >>>>>
> > >>>>> Booting with initcall_debug I see this with current Linux next:
> > >>>>>
> > >>>>> ...
> > >>>>> [    1.697313] cpuidle: using governor menu
> > >>>>> [    1.701353] initcall init_menu+0x0/0xc returned 0 after 0 usecs
> > >>>>> [    1.707458] calling  gpmc_init+0x0/0x10 @ 1
> > >>>>> [    1.711784] initcall gpmc_init+0x0/0x10 returned 0 after 0 usecs
> > >>>>> [    1.717974] calling  omap3_l3_init+0x0/0x10 @ 1
> > >>>>> [    1.722653] initcall omap3_l3_init+0x0/0x10 returned 0 after 0 usecs
> > >>>>> [    1.729201] calling  omap_l3_init+0x0/0x10 @ 1
> > >>>>> [    1.733791] initcall omap_l3_init+0x0/0x10 returned 0 after 0 usecs
> > >>>>> [    1.740314] calling  gate_vma_init+0x0/0x70 @ 1
> > >>>>> [    1.744976] initcall gate_vma_init+0x0/0x70 returned 0 after 0 usecs
> > >>>>> [    1.751522] calling  customize_machine+0x0/0x30 @ 1
> > >>>>> [    3.823114] initcall customize_machine+0x0/0x30 returned 0 after 2011718 usecs
> > >>>>> [    3.830566] calling  init_atags_procfs+0x0/0xec @ 1
> > >>>>> [    3.835583] No ATAGs?
> > >>>>
> > >>>> And the long time above with customize_machine() ends up being
> > >>>> pdata_quirks_init() calling of_platform_populate().
> > >>>
> > >>> That's what the delay is for me (I think I've reported that initially).
> > >>>
> > >>>>> Laurent & Tomi, care to check what you guys see in the slow booting case
> > >>>>> after booting with initcall_debug?
> > >>>>
> > >>>> But maybe the long delay is something else for you guys so please check.
> > >>>
> > >>
> > >> It's all devlink :( Looks like sometimes, improvements (PM) could became so complicated
> > >> that time required to execute such algorithms may completely eliminate all expected benefits.
> > >> Will not be surprised if PM consumption also increased instead of decreasing in some cases.
> > >>
> > >> not sure if it's 100% correct, but below diff reduces boot time
> > >> from 7.6sec to 3.7sec :P
> > >>
> > >> before:
> > >> [    0.053870] cpuidle: using governor menu
> > >> [    2.505971] No ATAGs?
> > >> ...
> > >> [    7.562317] Freeing unused kernel memory: 1024K
> > >>
> > >> after:
> > >> [    0.053800] cpuidle: using governor menu
> > >> [    0.136853] No ATAGs?
> > >> [    3.716218] devtmpfs: mounted
> > >> [    3.719628] Freeing unused kernel memory: 1024K
> > >> [    3.724266] Run /sbin/init as init process
> > >>
> > >> ----
> > >> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > >> index 071f04da32c8..e0cc37ed46ca 100644
> > >> --- a/drivers/of/platform.c
> > >> +++ b/drivers/of/platform.c
> > >> @@ -481,6 +481,7 @@ int of_platform_populate(struct device_node *root,
> > >>           pr_debug(" starting at: %pOF\n", root);
> > >>
> > >>           device_links_supplier_sync_state_pause();
> > >> +       fw_devlink_pause();
> > >>           for_each_child_of_node(root, child) {
> > >>                   rc = of_platform_bus_create(child, matches, lookup, parent, true);
> > >>                   if (rc) {
> > >> @@ -488,6 +489,7 @@ int of_platform_populate(struct device_node *root,
> > >>                           break;
> > >>                   }
> > >>           }
> > >> +       fw_devlink_resume();
> > >>           device_links_supplier_sync_state_resume();
> > >>
> > >>           of_node_set_flag(root, OF_POPULATED_BUS);
> > >> @@ -538,9 +540,7 @@ static int __init of_platform_default_populate_init(void)
> > >>           }
> > >>
> > >>           /* Populate everything else. */
> > >> -       fw_devlink_pause();
> > >>           of_platform_default_populate(NULL, NULL, NULL);
> > >> -       fw_devlink_resume();
> > >
> > > Your analysis is right, but this change is not safe. You'll get an
> > > unlocked linked list trampling if you call it outside of where it's
> > > called now. That's explicitly why I didn't do it the way this patch
> > > does it.
> > >
> > > To explain more, if you call fw_devlink_pause/resume() inside
> > > of_platform_populate() you can end up calling it in the context of
> > > another device's probe function. When a device's probe function is
> > > called, a has a bunch of other locks held and you'll cause a deadlock.
> > > To avoid that, I had to use defer_fw_devlink_lock to manage the list
> > > used by fw_devlink_pause/resume().
> > >
> > > I'll add more details later. But yeah, this patch isn't safe as is.
> >
> > I assume you going to fix it your way, right?
>
> I'll be glad to fix this if I find a way out. But currently, there's
> no "my way" for a generic fix to use inside of_platform_populate().
> However...
>
> > Just FYI. On ARM main DT population path is:
> >
> > arch_initcall(customize_machine)
> >         machine_desc->init_machine();
> >                 of_platform_default_populate();
> >                 -- or --
> >                 of_platform_populate();
> >
> > the of_platform_default_populate_init() called later due to make/linker dependencies.
> >
> > As result, existing pause/resume optimizations don't fully working.
>
> We can just add this optimization around all the other places the top
> level addition of DT devices is done. I wasn't aware of (more like
> forgot) the init_machine() path.
>
> Can you give the call path in your case? Just to make it a bit easier for me.

I think I have a simple solution. I can just move the
fw_devlink_pause/resume() inside of_platform_default_populate() and
call those only if "root" == NULL.

-Saravana