Re: [PATCH v1] pinctrl: baytrail: Move IRQ valid mask initialization to a dedicated callback

[Linus Walleij <linus.walleij@linaro.org>]

On Wed, Oct 30, 2019 at 10:31 AM Hans de Goede <hdegoede@redhat.com> wrote:

> The problem here is that gpiochip_add_data_with_key() calls gpiochip_irqchip_init_hw()
> before it calls gpiochip_irqchip_init_valid_mask(), so after commit 88583e340a0e
> when byt_gpio_irq_init_hw runs gc->irq.valid_mask is NULL and we crash with a NULL
> pointer exception (or so I believe, the kernel never gets far enough to get
> any info out of it without extra work).
>
> Note that this ("[PATCH v1] pinctrl: baytrail: Move IRQ valid mask initialization to a dedicated callback")
> patch fixes this since it moves the gc->irq.valid_mask accesses to
> byt_init_irq_valid_mask.

OK so we have a halfway fix there.

> But this change itself triggers another variant of this ordering issue,
> it causes these 2 new errors to get logged:
>
> byt_gpio INT33FC:01: GPIO interrupt error, pins misconfigured. INT_STAT0: 0x01800000
> byt_gpio INT33FC:02: GPIO interrupt error, pins misconfigured. INT_STAT0: 0x00400000
>
> The problem is that before this change the code calculating the valid_mask
> would also disable interrupts on GPIOs which do not have their
> BYT_DIRECT_IRQ_EN bit set. This now happens after the check done in
> byt_gpio_irq_init_hw() causing these false-positive error messages.

Isn't that easily fixed with something like this:

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 9afbc0612126..e865c889ba8d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1411,11 +1411,11 @@ int gpiochip_add_data_with_key(struct
gpio_chip *chip, void *data,

        machine_gpiochip_add(chip);

-       ret = gpiochip_irqchip_init_hw(chip);
+       ret = gpiochip_irqchip_init_valid_mask(chip);
        if (ret)
                goto err_remove_acpi_chip;

-       ret = gpiochip_irqchip_init_valid_mask(chip);
+       ret = gpiochip_irqchip_init_hw(chip);
        if (ret)
                goto err_remove_acpi_chip;

(I sent a separate patch for this.)

It isn't super-easy to know the right ordering semantics
for init_hw vs init_valid_mask I think. Sadly we need to
test it out in practice.

> Even if we ignore the NULL pointer deref problem for now and we ignore
> these 2 new error messages for now. Things are still broken with the
> current changes in pinctrl/intel.git/for-next switching to letting
> devm_gpiochip_add_data register the irqchip means that
> acpi_gpiochip_request_interrupts() gets called before
> gpiochip_add_pin_range() is called from pinctrl-baytrail.c, causing
> the GPIO lookup of any ACPI _AEI handlers to fail, resulting in
> errors like this one:
>
> byt_gpio INT33FC:02: Failed to request GPIO for pin 0x13: -517
>
> And none of the _AEI handlers working

I just vaguely understand this...

If what you're saying is that the Baytrail driver is dependent
on registering the pin ranges *before* registering the GPIO
chip can we then:

diff --git a/drivers/pinctrl/intel/pinctrl-baytrail.c
b/drivers/pinctrl/intel/pinctrl-baytrail.c
index beb26550c25f..b308567c5153 100644
--- a/drivers/pinctrl/intel/pinctrl-baytrail.c
+++ b/drivers/pinctrl/intel/pinctrl-baytrail.c
@@ -1549,16 +1549,20 @@ static int byt_gpio_probe(struct byt_gpio *vg)
                girq->handler = handle_bad_irq;
        }

-       ret = devm_gpiochip_add_data(&vg->pdev->dev, gc, vg);
+       /*
+        * Needs to happen first since the gpiochip is using pin
+        * control as back-end.
+        */
+       ret = gpiochip_add_pin_range(gc, dev_name(&vg->pdev->dev),
+                                    0, 0, vg->soc_data->npins);
        if (ret) {
-               dev_err(&vg->pdev->dev, "failed adding byt-gpio chip\n");
+               dev_err(&vg->pdev->dev, "failed to add GPIO pin range\n");
                return ret;
        }

-       ret = gpiochip_add_pin_range(&vg->chip, dev_name(&vg->pdev->dev),
-                                    0, 0, vg->soc_data->npins);
+       ret = devm_gpiochip_add_data(&vg->pdev->dev, gc, vg);
        if (ret) {
-               dev_err(&vg->pdev->dev, "failed to add GPIO pin range\n");
+               dev_err(&vg->pdev->dev, "failed adding byt-gpio chip\n");
                return ret;
        }

(Tell me if I should send this as a separate patch.)

It's not entirely logical to have this semantic ordering so
the extra comment explains it, I hope, in case it actually
works.

> TL;DR: commit 88583e340a0e ("pinctrl: intel: baytrail: Pass irqchip when adding gpiochip")
> breaks a bunch of stuff and should be dropped from pinctrl/intel.git/for-next
> and this needs some more work before it is ready for mainline.

I don't know if that is such a good idea if this is a global problem,
like something that would potentially disturb any ACPI-based
GPIO chip. We might leave something else broken even if we
fix the issue locally.

Yours,
Linus Walleij