lkml.org 
[lkml]   [2021]   [Oct]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
SubjectRe: [PATCH v4 2/2] drivers: bus: Delete CONFIG_SIMPLE_PM_BUS
On Tue, 26 Oct 2021 at 06:00, Saravana Kannan <saravanak@google.com> wrote:
>
> On Fri, Oct 22, 2021 at 10:00 AM Amit Pundir <amit.pundir@linaro.org> wrote:
> >
> > On Fri, 22 Oct 2021 at 05:13, Saravana Kannan <saravanak@google.com> wrote:
> > >
> > > On Thu, Oct 21, 2021 at 4:21 AM Amit Pundir <amit.pundir@linaro.org> wrote:
> > > >
> > > > Hi Saravana,
> > > >
> > > > This patch broke v5.15-rc6 on RB5 (sm8250 | qcom/qrb5165-rb5.dts).
> > > > I can't boot past this point https://www.irccloud.com/pastebin/raw/Nv6ZwHmW.
> > >
> > > Amit top posting? How did that happen? :)
> > >
> > > The fact you are seeing this issue is super strange though. The driver
> > > literally does nothing other than allowing some sync_state() callbacks
> > > to happen. I also grepped for the occurence of "simple-bus" in
> > > arch/arm64/boot/dts/qcom/ and the only instance for 8250 is for the
> > > soc node.
> > >
> > > The only thing I can think of is that without my patch some
> > > sync_state() callbacks weren't getting called and maybe it was masking
> > > some other issue.
> > >
> > > Can you try to boot with this log (see log patch below) and see if the
> > > device hangs right after a sync_state() callback? Also, looking at the
> > > different sync_state() implementations in upstream, I'm guessing one
> > > of the devices isn't voting for interconnect bandwidth when it should
> > > have.
> > >
> > > Another thing you could do is boot without the simple-bus changes and
> > > then look for all instances of "state_synced" in /sys/devices and then
> > > see if any of them has the value "0" after boot up is complete.
> >
> > Turned out RB5 is not even reaching up to
> > device_links_flush_sync_list() and seem to be stuck somewhere in
> > device_links_driver_bound(). So I added more print logs to narrow down
> > to any specific lock state but those additional prints seem to have
> > added enough delay to unblock that particular driver (Serial:
> > 8250/16550 driver if I understood the logs correctly) and I eventually
> > booted to UI.
>
> Ugh... I think I know what's going on. It popped into my head over the weekend.
>
> Couple of ways to confirm my theory:
> 1. After it finishes booting in both cases, can you compare the output
> of the command below? I'm expecting to see a significant drop in the
> number of device links.
> ls -l /sys/class/devlink | wc -l
>

On a successful boot with debug prints:
rb5:/ $ ls -l /sys/class/devlink | wc -l
245

Booting with this SIMPLE_PM_BUS patch reverted:
rb5:/ $ ls -l /sys/class/devlink | wc -l
248

> 2. Can you try out this terrible hack patch (not final fix, no code
> reviews please) on top of Tot to see if it fixes your issue without
> having to add hacky logs?
>

No luck booting with the following hack patch either.

Regards,
Amit Pundir


> Thanks,
> Saravana
>
> --- a/drivers/bus/simple-pm-bus.c
> +++ b/drivers/bus/simple-pm-bus.c
> @@ -38,10 +38,12 @@ static int simple_pm_bus_probe(struct platform_device *pdev)
> * a device that has a more specific driver.
> */
> if (match && match->data) {
> - if (of_property_match_string(np, "compatible",
> match->compatible) == 0)
> + if (of_property_match_string(np, "compatible",
> match->compatible) == 0) {
> + of_platform_populate(np, NULL, lookup, &pdev->dev);
> return 0;
> - else
> + } else {
> return -ENODEV;
> + }
> }

\
 
 \ /
  Last update: 2021-10-26 19:51    [W:2.102 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site