[Linux-kernel-mentees] Any other ways to debug GPIO interrupt controller (pinctrl-amd) for broken touchpads of a new laptop model?

Hans de Goede hdegoede at redhat.com
Fri Oct 2 13:36:29 UTC 2020


On 10/2/20 2:42 PM, Coiby Xu wrote:
> On Fri, Oct 02, 2020 at 11:40:12AM +0200, Hans de Goede wrote:
>> Hi,
>> On 10/1/20 10:57 PM, Linus Walleij wrote:
>>> Sorry for top posting, but I want to page some people.
>>> I do not know anything about ACPI, but Hans de Goede is really
>>> good with this kind of things and could possibly provide some
>>> insight.
>> Thanks, although I'm honored to be considered the go to person
>> for these kinda things my specialty really lies with these
>> kinda issues with intel Bay Trail and Cherry Trail SoCs
>> never the less let me take a look.
> Thank you for taking time to examine this touchpad issue!
>>> On Thu, Oct 1, 2020 at 3:23 PM Coiby Xu <coiby.xu at gmail.com> wrote:
>>>> Hi,
>>>> I'm trying to fix broken touchpads [1] for a new laptop model Legion-5
>>>> 15ARH05 which is shipped with two different touchpads, i.e., ElAN and
>>>> Synaptics. For the ELAN touchpad, the kernel receives no interrupts to
>>>> be informed of new data from the touchpad. For the Synaptics touchpad,
>>>> only 7 interrupts are received per second which makes the touchpad
>>>> completely unusable. Based on current observations, pinctrl-amd seems to
>>>> be the most suspicious cause.
>>>> Why do I think pinctrl-amd smells the most suspicious?
>>>> ======================================================
>>>> This laptop model has the following hardware configurations specified
>>>> via ACPI,
>>>>   - The touchpad's data interrupt line is connected to pin#130 of a GPIO
>>>>     chip
>>>>          GpioInt (Level, ActiveLow, ExclusiveAndWake, PullUp, 0x0000,
>>>>                          "\\_SB.GPIO", 0x00, ResourceConsumer, ,
>>>>                          )
>>>>                          {   // Pin list
>>>>                              0x0082
>>>>                          }
>>>>   - This GPIO chip (HID: AMDI0030) which is assigned with IRQ#7 has its
>>>>     common interrupt output line connected to one IO-APIC's pin#7
>>>>          Interrupt (ResourceConsumer, Level, ActiveLow, Shared, ,, )
>>>>          {
>>>>              0x00000007,
>>>>          }
>> So these both look fine.
>>>> I add some code to kernel to poll the status of the GPIO chip's pin#130
>>>> and IO-APIc's pin#7 every 1ms when I move my finger on the surface of
>>>> the Synaptics touchpad continuously for about 1s. During the process of I
>>>> move my finger, most of the time,
>>>>   - GPIO chip's pin#130: low input, interrupt unmasked
>>>>   - IO-APIC's pin#7: IRR=0, interrupt unmasked (in fact mask/unmask_ioapic_irq
>>>>     have never been called by the IRQ follow controller handle_fasteoi_irq)
>>>> So the touchpad has been generating interrupts most of the time while
>>>> IO-APIC controller hasn't been masking the interrupt from the GPIO chip.
>>>> But somehow the kernel could only get ~7 interrupts each second
>> So are you seeing these 7 interrupts / second for the touchpad irq or for
>> the GPIO controllers parent irq ?
>> Also to these 7 interrupts/sec stop happening when you do not touch the
>> touchpad ?
> I see these 7 interrupts / second for the GPIO controller's parent irq.
> And they stop happening when I don't touch the touchpad.

Only from the parent irq, or also on the touchpad irq itself ?

If this only happens on the parent irq, then I would start looking at the
amd-pinctrl code which determines which of its "child" irqs to fire.

>> To me this sounds like the interrupt is configured as being triggered on
>> a negative edge so that it only fires once when the line from the touchpad
>> goes low, and for some reason 7 times a second the touchpad controller
>> briefly releases the line (sorta gives up to signal the irq and then
>> tries again?).
>>>> while
>>>> the touchpad could generate 140 interrupts (time resolution of 7.2ms)
>>>> per second. Assuming IO-APIC (arch/x86/kernel/apic/io_apic.c) is fine,
>>>> then there's something wrong with the GPIO interrupt controller which
>>>> works fine for the touchpad under Windows. Besides if I poll the touchpad
>>>> data based on pin#130's status, the touchpad could also work under
>>>> Windows.
>> I agree that this sounds like a problem with the GpioInt handling.
>>>> Ways to debug pinctrl-amd
>>>> =========================
>>>> I can't find any documentation about the AMDI0030 GPIO chip except for
>>>> the commit logs of drivers/pinctrl/pinctrl-amd. One commit
>>>> ba714a9c1dea85e0bf2899d02dfeb9c70040427c ("pinctrl/amd: Use regular interrupt instead of chained")
>>>> inspired me to bring back chained interrupt to see if "an interrupt storm"
>>>> would happen. The only change I noticed is that the interrupts arrive in
>>>> pairs. The time internal between two interrupts in a pair is ~0.0016s
>>>> but the time internal between interrupt pairs is still ~0.12s (~8Hz).
>>>> Unfortunately, I don't get any insight about the GPIO interrupt
>>>> controller from this tweaking. I wonder if there are any other ways
>>>> to debug drivers/pinctrl/pinctrl-amd?
>> The way I would try to debug this (with access to the hardware) is
>> to try an verify the interrupt trigger (level vs edge) settings inside
>> pinctrl/amd by adding a bunch of printks printing them whenever the
>> relevant register bits are touched.
>> So I'm going to guess here that these touchpads use i2c-hid, so I
>> took a quick peak at the i2c-hid irq request code from
>> drivers/hid/i2c-hid/i2c-hid-core.c:
>>        unsigned long irqflags = 0;
>>        int ret;
>>        dev_dbg(&client->dev, "Requesting IRQ: %d\n", client->irq);
>>        if (!irq_get_trigger_type(client->irq))
>>                irqflags = IRQF_TRIGGER_LOW;
>>        ret = request_threaded_irq(client->irq, NULL, i2c_hid_irq,
>>                                   irqflags | IRQF_ONESHOT, client->name, ihid);
>> So this tries to preserve the pre-configured irq-type on the irq
>> line and if no irq-type is set then it overrides the trigger-type
>> to IRQF_TRIGGER_LOW, which means level-low.
>> One quick hack you can try is ommenting out the "if (!irq_get_trigger_type(client->irq))"
>> type, I guess maybe the pinctrl-amd code is defaulting all IRQs to some
>> edge trigger type? This should override it and recontrol it to
>> a level trigger type.
> Yes, "these touchpads use i2c-hid". I have examined the configuration of
> irq-type in drivers/hid/i2c-hid/i2c-hid-core.c and can confirm it's been
> configured to be level-low.
> $ sudo cat /sys/kernel/debug/gpio|grep -A1 pin130
> 260:pin130      Level trigger| Active low| interrupt is enabled| interrupt is unmasked| disable wakeup in S0i3 state| disable wakeup in S3 state|
> (Of course we rely on drivers/pinctrl/pinctrl-amd.c to read&interpret
> data from the corresponding registers. If pinctrl-amd is return false
> reports, we can do nothing about this)

Well you could review the code printing this vs say the code setting
the trigger type. If those don't match then something is definitely
wrong somewhere.

> Btw, we can't make any change in i2c-hid because they will be overridden
> by drivers/pinctrl/pinctrl-amd.c which use the values from the ACPI tables
> instead,
> static int amd_gpio_irq_set_type(struct irq_data *d, unsigned int type)
> {
>      /* Ignore the settings coming from the client and
>       * read the values from the ACPI tables
>       * while setting the trigger type
>       */
>      irq_flags = irq_get_trigger_type(d->irq);
>      if (irq_flags != IRQ_TYPE_NONE)
>          type = irq_flags;
> }

That looks a bit fishy, sometimes we need to override the irq-type from
a driver because the ACPI tables of various devices are often of
dubious quality. AFAIK non of the Intel GPIO drivers do something like

Also I'm not seeing this in the latest upstream code, so I guess this
bit got recently dropped ... ?

What kernel version are you testing with? You really should always test
things like this with Linus' latest master branch.

Hmm, I wonder if this is not an i2c-controller issue instead. But you should
that you tried to modify the i2c-hid code to poll the GPIO and then run its
threaded-irq handler on a successfull poll instead works around things, right ?

Still it would be interesting to add a printk to the begin + end of the
i2c-hid threaded-irq-handler to see how long it takes to run.



> Also, With CONFIG_GENERIC_IRQ_DEBUGFS enabled, `cat /sys/kernel/debug/irq/irqs/72`
> also shows irq#72 (#72 is requested IRQ of this touchpad device) has the
> expected irq-type,
> $ cat /sys/kernel/debug/irq/irqs/72
> handler:  handle_level_irq
> device:   (null)
> status:   0x00000508
>              _IRQ_NOPROBE
> istate:   0x00000020
>              IRQS_ONESHOT
> ddepth:   0
> wdepth:   0
> dstate:   0x00402208
>              IRQ_TYPE_LEVEL_LOW
>              IRQD_LEVEL
>              IRQD_ACTIVATED
>              IRQD_IRQ_STARTED`
>> ###
>> As you said hopefully the IOApic code is fine. Notice that the ioapic
>> irqchip driver does not allow configuring the trigger type.
> Yes. unlike pinctrl-amd, arch/x86/kernel/apic/io_apic.c doesn't provide
> `(struct irq_chip*)->irq_set_type`. I notice during the setting-up of
> ia-apic, all pins are configured with edge-high according to the IRQ
> redirection table which can be printed out with the "apic=debug" kernel
> parameter,
>      .... IRQ redirection table:
>      IOAPIC 0:
>       pin00, disabled, edge , high, V(00), IRR(0), S(0), physical, D(00), M(0)
>       pin06, enabled , edge , high, V(06), IRR(0), S(0), physical, D(00), M(0)
>       pin07, disabled, edge , high, V(00), IRR(0), S(0), physical, D(00), M(0)
> Later, I manually printed out the IRQ redirection table when processing
> touchpad HID reports, pin07 (which is connected with the GPIO's common
> interrupt output line) has adopted the expected configuration,
>      pin07, enabled , level, low , V(07), IRR(1), S(0), physical, D(00), M(0)
> Today I played with the "noapic" kernel parameter to use PIC mode
> so we can confirm there is nothing wrong with io-apic. Unfortunately
> the I2C adapter can't be set-up (the error is "controller timed out").
> As a consequence, the touchpad as an I2C client won't work either.
> And I can't find a way to disable APIC for Windows either.
>> I guess
>> this is not part of the ioapic spec and that the BIOS/firmware is setting
>> the triggerlevel in a io-apic implementation specific way, so we better hope
>> it is right. I have had the unfortunate experience to try and debug a wrong
>> io-apic irq-pin trigger-type issue with TPMs in some Lenovo thinkpads and
>> in the end only the Lenovo BIOS team could fix this.
> If the same BIOS/firmware is setting the trigger level in a wrong way,
> shouldn't we find the same issue under Windows? Btw, I've set
> 'acpi_osi="Windows 2015"'
> as the kernel parameter before but I didn't notice any change.
>> Regards,
>> Hans
> -- 
> Best regards,
> Coiby

More information about the Linux-kernel-mentees mailing list