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    SubjectRe: [PATCH 4.4 093/113] pinctrl: msm: Really mask level interrupts to prevent latching
    On Mon, Oct 08, 2018 at 11:33:38PM -0700, Nathan Chancellor wrote:
    > On Mon, Oct 08, 2018 at 08:31:34PM +0200, Greg Kroah-Hartman wrote:
    > > 4.4-stable review patch. If anyone has any objections, please let me know.
    > >
    > > ------------------
    > >
    > > From: Stephen Boyd <swboyd@chromium.org>
    > >
    > > [ Upstream commit b55326dc969ea2d704a008d9a97583b128f54f4f ]
    > >
    > > The interrupt controller hardware in this pin controller has two status
    > > enable bits. The first "normal" status enable bit enables or disables
    > > the summary interrupt line being raised when a gpio interrupt triggers
    > > and the "raw" status enable bit allows or prevents the hardware from
    > > latching an interrupt into the status register for a gpio interrupt.
    > > Currently we just toggle the "normal" status enable bit in the mask and
    > > unmask ops so that the summary irq interrupt going to the CPU's
    > > interrupt controller doesn't trigger for the masked gpio interrupt.
    > >
    > > For a level triggered interrupt, the flow would be as follows: the pin
    > > controller sees the interrupt, latches the status into the status
    > > register, raises the summary irq to the CPU, summary irq handler runs
    > > and calls handle_level_irq(), handle_level_irq() masks and acks the gpio
    > > interrupt, the interrupt handler runs, and finally unmask the interrupt.
    > > When the interrupt handler completes, we expect that the interrupt line
    > > level will go back to the deasserted state so the genirq code can unmask
    > > the interrupt without it triggering again.
    > >
    > > If we only mask the interrupt by clearing the "normal" status enable bit
    > > then we'll ack the interrupt but it will continue to show up as pending
    > > in the status register because the raw status bit is enabled, the
    > > hardware hasn't deasserted the line, and thus the asserted state latches
    > > into the status register again. When the hardware deasserts the
    > > interrupt the pin controller still thinks there is a pending unserviced
    > > level interrupt because it latched it earlier. This behavior causes
    > > software to see an extra interrupt for level type interrupts each time
    > > the interrupt is handled.
    > >
    > > Let's fix this by clearing the raw status enable bit for level type
    > > interrupts so that the hardware stops latching the status of the
    > > interrupt after we ack it. We don't do this for edge type interrupts
    > > because it seems that toggling the raw status enable bit for edge type
    > > interrupts causes spurious edge interrupts.
    > >
    > > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
    > > Reviewed-by: Douglas Anderson <dianders@chromium.org>
    > > Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
    > > Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
    > > Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > > ---
    > > drivers/pinctrl/qcom/pinctrl-msm.c | 24 ++++++++++++++++++++++++
    > > 1 file changed, 24 insertions(+)
    > >
    > > --- a/drivers/pinctrl/qcom/pinctrl-msm.c
    > > +++ b/drivers/pinctrl/qcom/pinctrl-msm.c
    > > @@ -577,6 +577,29 @@ static void msm_gpio_irq_mask(struct irq
    > > spin_lock_irqsave(&pctrl->lock, flags);
    > >
    > > val = readl(pctrl->regs + g->intr_cfg_reg);
    > > + /*
    > > + * There are two bits that control interrupt forwarding to the CPU. The
    > > + * RAW_STATUS_EN bit causes the level or edge sensed on the line to be
    > > + * latched into the interrupt status register when the hardware detects
    > > + * an irq that it's configured for (either edge for edge type or level
    > > + * for level type irq). The 'non-raw' status enable bit causes the
    > > + * hardware to assert the summary interrupt to the CPU if the latched
    > > + * status bit is set. There's a bug though, the edge detection logic
    > > + * seems to have a problem where toggling the RAW_STATUS_EN bit may
    > > + * cause the status bit to latch spuriously when there isn't any edge
    > > + * so we can't touch that bit for edge type irqs and we have to keep
    > > + * the bit set anyway so that edges are latched while the line is masked.
    > > + *
    > > + * To make matters more complicated, leaving the RAW_STATUS_EN bit
    > > + * enabled all the time causes level interrupts to re-latch into the
    > > + * status register because the level is still present on the line after
    > > + * we ack it. We clear the raw status enable bit during mask here and
    > > + * set the bit on unmask so the interrupt can't latch into the hardware
    > > + * while it's masked.
    > > + */
    > > + if (irqd_get_trigger_type(d) & IRQ_TYPE_LEVEL_MASK)
    > > + val &= ~BIT(g->intr_raw_status_bit);
    > > +
    > > val &= ~BIT(g->intr_enable_bit);
    > > writel(val, pctrl->regs + g->intr_cfg_reg);
    > >
    > > @@ -598,6 +621,7 @@ static void msm_gpio_irq_unmask(struct i
    > > spin_lock_irqsave(&pctrl->lock, flags);
    > >
    > > val = readl(pctrl->regs + g->intr_cfg_reg);
    > > + val |= BIT(g->intr_raw_status_bit);
    > > val |= BIT(g->intr_enable_bit);
    > > writel(val, pctrl->regs + g->intr_cfg_reg);
    > >
    > >
    > >
    >
    > Sigh, sorry, I caught this after I sent my initial all good email but
    > this commit breaks NFC on my Pixel 2 XL (toggle becomes greyed out and
    > apps that want to use it ask to enable it). I can't say why, I'm more
    > than happy to debug but I'm assuming it's some voodoo that Qualcomm has
    > done out of tree. I'll leave it up to you how to proceed given that I
    > can't run mainline :(

    Ugh, I hate the qualcomm changes...

    Given the mess that all of the msm driver changes have, I'll go drop
    this patch from the stable tree as I don't want to deal with the
    fall-out for when people merge this to their device-specific trees.

    thanks for testing and letting me know about this.

    greg k-h

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