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Message-ID: <CAMuHMdVVgB7KZq7-u-pAC-cZvVLWkv5wM4HC_jW7WK_tz52+cg@mail.gmail.com> Date: Wed, 20 Jul 2022 19:31:01 +0200 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Saravana Kannan <saravanak@...gle.com> Cc: 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>, Android Kernel Team <kernel-team@...roid.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org>, Linux IOMMU <iommu@...ts.linux-foundation.org>, netdev <netdev@...r.kernel.org>, "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>, Wolfram Sang <wsa+renesas@...g-engineering.com>, Linux-Renesas <linux-renesas-soc@...r.kernel.org> Subject: Re: [PATCH v2 6/9] Revert "driver core: Set default deferred_probe_timeout back to 0." Hi Saravana, On Wed, Jun 1, 2022 at 9:45 AM Saravana Kannan <saravanak@...gle.com> wrote: > This reverts commit 11f7e7ef553b6b93ac1aa74a3c2011b9cc8aeb61. > > Let's take another shot at getting deferred_probe_timeout=10 to work. > > Signed-off-by: Saravana Kannan <saravanak@...gle.com> Thanks for your patch, which is now commit f516d01b9df2782b ("Revert "driver core: Set default deferred_probe_timeout back to 0."") in driver-core/driver-core-next. Wolfram found an issue on a Renesas board where disabling the IOMMU driver (CONFIG_IPMMU_VMSA=n) causes the system to fail to boot, and bisected this to a merge of driver-core/driver-core-next. After some trials, I managed to reproduce the issue, and bisected it further to commit f516d01b9df2782b. The affected config has: CONFIG_MODULES=y CONFIG_RCAR_DMAC=y CONFIG_IPMMU_VMSA=n In arch/arm64/boot/dts/renesas/r8a77951-salvator-xs.dtb, e6e88000.serial links to a dmac, and the dmac links to an iommu, for which no driver is available. Playing with deferred_probe_timeout values doesn't help. However, the above options do not seem to be sufficient to trigger the issue, as I had other configs with those three options that do boot fine. After bisecting configs, I found the culprit: CONFIG_IP_PNP. As Wolfram was using an initramfs, CONFIG_IP_PNP was not needed. If CONFIG_IP_PNP=n, booting fails. If CONFIG_IP_PNP=y, booting succeeds. In fact, just disabling late_initcall(ip_auto_config) makes it fail, too. Reducing ip_auto_config(), it turns out the call to wait_for_init_devices_probe() is what is needed to unblock booting. So I guess wait_for_init_devices_probe() needs to be called (where?) if CONFIG_IP_PNP=n, too? > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -256,7 +256,12 @@ static int deferred_devs_show(struct seq_file *s, void *data) > } > DEFINE_SHOW_ATTRIBUTE(deferred_devs); > > +#ifdef CONFIG_MODULES > +int driver_deferred_probe_timeout = 10; > +#else > int driver_deferred_probe_timeout; > +#endif > + > EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout); > > static int __init deferred_probe_timeout_setup(char *str) Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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