[PATCH v4] pinctrl: qcom: Assign irq_eoi conditionally

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

The hierarchical parts of MSM pinctrl/GPIO is only
used when the device tree has a "wakeup-parent" as
a phandle, but the .irq_eoi is anyway assigned leading
to semantic problems on elder Qualcomm chipsets.

When the drivers/mfd/qcom-pm8xxx.c driver calls
chained_irq_exit() that call will in turn call chip->irq_eoi()
which is set to irq_chip_eoi_parent() by default on a
hierachical IRQ chip, and the parent is pinctrl-msm.c
so that will in turn unconditionally call
irq_chip_eoi_parent() again, but its parent is invalid
so we get the following crash:

 Unnable to handle kernel NULL pointer dereference at
 virtual address 00000010
 pgd = (ptrval)
 [00000010] *pgd=00000000
 Internal error: Oops: 5 [#1] PREEMPT SMP ARM
 (...)
 PC is at irq_chip_eoi_parent+0x4/0x10
 LR is at pm8xxx_irq_handler+0x1b4/0x2d8

If we solve this crash by avoiding to call up to
irq_chip_eoi_parent(), the machine will hang and get
reset by the watchdog, because of semantic issues,
probably inside irq_chip.

As a solution, just assign the .irq_eoi conditionally if
we are actually using a wakeup parent.

Cc: David Heidelberg <david@xxxxxxx>
Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Cc: Lina Iyer <ilina@xxxxxxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: e35a6ae0eb3a ("pinctrl/msm: Setup GPIO chip in hierarchy")
Link: https://lore.kernel.org/r/20200306121221.1231296-1-linus.walleij@xxxxxxxxxx
Link: https://lore.kernel.org/r/20200309125207.571840-1-linus.walleij@xxxxxxxxxx
Tested-by: David Heidelberg <david@xxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
ChangeLog v3->v4:
- Fix the patch subject too, doh.
ChangeLog v2->v3:
- Keep .irq_disable() around, just make the assignment of
  .irq_eoi() conditional.
ChangeLog v1->v2:
- Noticed that the previous solution doesn't actually work,
  the machine hangs and reboots intead (even if it got rid of
  the most obvious crash). Make a more thorough solution that
  completely avoids using these callbacks if we don't have
  a parent.
- v1 was called "Guard irq_eoi()"
---
 drivers/pinctrl/qcom/pinctrl-msm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c
index 9a8daa256a32..1a948c3f54b7 100644
--- a/drivers/pinctrl/qcom/pinctrl-msm.c
+++ b/drivers/pinctrl/qcom/pinctrl-msm.c
@@ -1104,7 +1104,6 @@ static int msm_gpio_init(struct msm_pinctrl *pctrl)
 	pctrl->irq_chip.irq_mask = msm_gpio_irq_mask;
 	pctrl->irq_chip.irq_unmask = msm_gpio_irq_unmask;
 	pctrl->irq_chip.irq_ack = msm_gpio_irq_ack;
-	pctrl->irq_chip.irq_eoi = irq_chip_eoi_parent;
 	pctrl->irq_chip.irq_set_type = msm_gpio_irq_set_type;
 	pctrl->irq_chip.irq_set_wake = msm_gpio_irq_set_wake;
 	pctrl->irq_chip.irq_request_resources = msm_gpio_irq_reqres;
@@ -1118,7 +1117,7 @@ static int msm_gpio_init(struct msm_pinctrl *pctrl)
 		if (!chip->irq.parent_domain)
 			return -EPROBE_DEFER;
 		chip->irq.child_to_parent_hwirq = msm_gpio_wakeirq;
-
+		pctrl->irq_chip.irq_eoi = irq_chip_eoi_parent;
 		/*
 		 * Let's skip handling the GPIOs, if the parent irqchip
 		 * is handling the direct connect IRQ of the GPIO.
-- 
2.24.1