Simon Horman reported that Koelsch and Lager hang during boot, and
bisected this to commit 1c3c5eab ("sched/core: Enable
might_sleep() and smp_processor_id() checks early").

The da9063/da9210 regulator quirk for R-Car Gen2 boards uses a bus
notifier, and unregisters the notifier when it is no longer needed.
However, a notifier must not be unregistered from within the call chain.

This bug went unnoticed, as blocking_notifier_chain_unregister() didn't
take the semaphore during early boot.  The aforementioned commit changed
that behavior, leading to a deadlock.

Fix this by removing the call to bus_unregister_notifier(), and keeping
local completion state instead.
Reported-by: NSimon Horman <horms+renesas@verge.net.au>
Fixes: 663fbb52 ("ARM: shmobile: R-Car Gen2: Add da9063/da9210 regulator quirk")
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

The current implementation only works if the da9xxx devices are added
before their drivers are registered. Only then it can apply the fixes to
both devices. Otherwise, the driver for the first device gets probed
before the fix for the second device can be applied. This is what
fails when using the IP core switcher or when having the i2c master
driver as a module.

So, we need to disable both da9xxx once we detected one of them. We now
use i2c_transfer with hardcoded i2c_messages and device addresses, so we
don't need the da9xxx client devices to be instantiated. Because the
fixup is used on specific boards only, the addresses are not going to
change.

Fixes: 663fbb52 ("ARM: shmobile: R-Car Gen2: Add da9063/da9210 regulator quirk")
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> (r8a7791/koelsch)
Tested-by: NKuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

Regulator setup seems identical to Koelsch.
Signed-off-by: NUlrich Hecht <ulrich.hecht+renesas@gmail.com>
Acked-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

The r8a7790/lager and r8a7791/koelsch development boards have da9063 and
da9210 regulators.  Both regulators have their interrupt request lines
tied to the same interrupt pin (IRQ2) on the SoC.

After cold boot or da9063-induced restart, both the da9063 and da9210
seem to assert their interrupt request lines.  Hence as soon as one
driver requests this irq, it gets stuck in an interrupt storm, as it
only manages to deassert its own interrupt request line, and the other
driver hasn't installed an interrupt handler yet.

To handle this, install a quirk that masks the interrupts in both the
da9063 and da9210.  This quirk has to run after the i2c master driver
has been initialized, but before the i2c slave drivers are initialized.
As it depends on i2c, select I2C if one of the affected platforms is
enabled in the kernel config.

On koelsch, the following happens:

  - Cold boot or reboot using the da9063 restart handler:

	IRQ2 is asserted, installing da9063/da9210 regulator quirk
	...
	i2c i2c-6: regulator_quirk_notify: 1, IRQC_MONITOR = 0x3fb
	i2c 6-0058: regulator_quirk_notify: 1, IRQC_MONITOR = 0x3fb
	i2c 6-0058: Detected da9063
	i2c 6-0058: Masking da9063 interrupt sources
	i2c 6-0068: regulator_quirk_notify: 1, IRQC_MONITOR = 0x3fb
	i2c 6-0068: Detected da9210
	i2c 6-0068: Masking da9210 interrupt sources
	i2c 6-0068: IRQ2 is not asserted, removing quirk

  - Warm boot (reset button):

	rcar_gen2_regulator_quirk: IRQ2 is not asserted, not installing quirk
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Tested-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>