Re: [PATCH 2/3] irqchip: SigmaStar SSD20xD gpi

From: Daniel Palmer <daniel@0x0f.com>
To: Marc Zyngier <maz@kernel.org>
Cc: DTML <devicetree@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Romain Perier <romain.perier@gmail.com>
Subject: Re: [PATCH 2/3] irqchip: SigmaStar SSD20xD gpi
Date: Tue, 21 Sep 2021 15:11:35 +0900	[thread overview]
Message-ID: <CAFr9PXm8S+P+q5KiU7DxeKQVU92PQefovjd25zrQJ2m2RyZpcg@mail.gmail.com> (raw)
In-Reply-To: <87wnnbv6ac.wl-maz@kernel.org>

Hi Marc,

Sorry for the constant email.

On Mon, 20 Sept 2021 at 20:24, Marc Zyngier <maz@kernel.org> wrote:
>
> On Mon, 20 Sep 2021 11:05:26 +0100,
> Daniel Palmer <daniel@0x0f.com> wrote:
> >
> > Hi Marc,
> >
> > On Mon, 20 Sept 2021 at 18:45, Marc Zyngier <maz@kernel.org> wrote:
> > > > +static void ssd20xd_gpi_unmask_irq(struct irq_data *data)
> > > > +{
> > > > +     irq_hw_number_t hwirq = irqd_to_hwirq(data);
> > > > +     struct ssd20xd_gpi *gpi = irq_data_get_irq_chip_data(data);
> > > > +     int offset_reg = REG_OFFSET(hwirq);
> > > > +     int offset_bit = BIT_OFFSET(hwirq);
> > > > +
> > > > +     regmap_update_bits(gpi->regmap, REG_MASK + offset_reg, offset_bit, 0);
> > >
> > > Is this regmap call atomic? When running this, you are holding a
> > > raw_spinlock already. From what I can see, this is unlikely to work
> > > correctly with the current state of regmap.
> >
> > I didn't even think about it. I will check.
>
> You may want to enable lockdep to verify that.

After some research I think this can be solved by adding
".use_raw_spinlock = true" to the regmap config to force using a
raw_spinlock instead of the default spinlock.
This avoids having a spinlock inside of a raw_spinlock.

lockdep doesn't actually complain about this currently but another
interrupt controller driver I have uses a syscon because the interrupt
registers are mixed in with unrelated stuff.
lockdep is complaining about the spinlock inside of a raw_spinlock
there. So I guess I'll need to add a new DT property for syscon to use
raw_spinlocks for that driver.

Cheers,

Daniel