Re: [PATCH v2 6/9] Revert "driver core: Set default deferred_probe_timeout back to 0."
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2022-07-20 17:37:29
Also in:
linux-gpio, linux-pm, linux-renesas-soc, lkml
Hi Saravana, On Wed, Jun 1, 2022 at 9:45 AM Saravana Kannan [off-list ref] wrote:
This reverts commit 11f7e7ef553b6b93ac1aa74a3c2011b9cc8aeb61. Let's take another shot at getting deferred_probe_timeout=10 to work. Signed-off-by: Saravana Kannan <redacted>
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?
quoted hunk ↗ jump to hunk
--- 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@linux-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