On Thu, Oct 1, 2020 at 5:56 AM Grygorii Strashko
<grygorii.strashko@xxxxxx> 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@xxxxxxxxxxx> [201001 07:53]:
> >>> * Peter Ujfalusi <peter.ujfalusi@xxxxxx> [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.
-Saravana
