Re: [PATCH v4 2/2] drivers: bus: Delete CONFIG_SIMPLE_PM_BUS

From: Saravana Kannan <saravanak@google.com>
To: Amit Pundir <amit.pundir@linaro.org>
Cc: Russell King <linux@armlinux.org.uk>,
	Neil Armstrong <narmstrong@baylibre.com>,
	 Geert Uytterhoeven <geert+renesas@glider.be>,
	Magnus Damm <magnus.damm@gmail.com>,
	 Tony Lindgren <tony@atomide.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Will Deacon <will@kernel.org>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	 Rob Herring <robh+dt@kernel.org>,
	Android Kernel Team <kernel-team@android.com>,
	linux-arm-kernel@lists.infradead.org,
	lkml <linux-kernel@vger.kernel.org>,
	 linux-oxnas@groups.io, linux-renesas-soc@vger.kernel.org,
	 linux-omap@vger.kernel.org, linux-riscv@lists.infradead.org,
	 Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	John Stultz <john.stultz@linaro.org>
Subject: Re: [PATCH v4 2/2] drivers: bus: Delete CONFIG_SIMPLE_PM_BUS
Date: Thu, 21 Oct 2021 16:42:34 -0700	[thread overview]
Message-ID: <CAGETcx_YZOd05Gg53ZR8mfVhFUzwQWo4MrrWF8JHF_DCwEtunw@mail.gmail.com> (raw)
In-Reply-To: <CAMi1Hd0HvPOT277mx8hNTU9NQH2ti7h5qc5+rxOkRWwbfrhyQQ@mail.gmail.com>

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.

-Saravana

-- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1099,6 +1099,7 @@ static void device_links_flush_sync_list(struct
list_head *list,
                if (dev != dont_lock_dev)
                        device_lock(dev);

+               dev_info(dev, "Calling sync_state()\n");
                if (dev->bus->sync_state)
                        dev->bus->sync_state(dev);
                else if (dev->driver && dev->driver->sync_state)

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