[alsa-devel] ASoC: Intel: sst: Missing IRQ at index 5 on BYT-T device

[Stephan Gerhold]

On Mon, Dec 17, 2018 at 08:52:46AM -0600, Pierre-Louis Bossart wrote:
> 
> On 12/16/18 12:54 PM, Stephan Gerhold wrote:
> > Hi,
> > 
> > I have an Intel Bay Trail (BYT-T) tablet that was originally shipped
> > with Android. With the right quirks, bytcr-rt5640 is working fine, but
> > there is a problem in sst_acpi.c that is preventing it from working
> > with a mainline kernel:
> > 
> > Even though this is a BYT-T device, there is no IRQ at index 5 in the
> > ACPI DSDT table. This means that SST will fail to probe, and actually
> > leads to a NULL pointer dereference later when the ALSA device is first
> > opened. (I have submitted a possible solution for this as
> > "[PATCH] ASoC: Intel: sst: Delay machine device creation until after
> > initialization")
> > 
> > The correct IRQ is actually located on index 0, just like it is already
> > being used for BYT-CR devices. So if I force is_byt_cr() to return TRUE,
> > everything works as expected.
> 
> So the root cause of your problem is that the detection of byt-cr doesn't
> work? That would be a first.

No. is_byt_cr() works correctly, as my device is a BYT-T (not a BYT-CR)
device. :)

The problem here is that the kernel expects the IRQ at index 5 for BYT-T 
devices, but my device has only a single IRQ listed. Forcing is_byt_cr() 
to return TRUE is just a workaround to make it use the IRQ at index 0 
(which is the correct one).

Currently, sst_acpi supports these two variations:
  - BYT-T:  5 IRQs listed -> acpi_ipc_irq_index = 5
  - BYT-CR: 5 IRQs listed -> acpi_ipc_irq_index = 0

On my device (and a few other Android based BYT-T devices) I have found:
  - BYT-T:  1 IRQ  listed -> acpi_ipc_irq_index = 0
but at the moment the kernel attempts to use acpi_ipc_irq_index = 5 from
BYT-T above.

> 
> Can you please double-check that CONFIG_IOSF_MBI is enabled and provide a
> trace of the bios status in this piece of code:
> 
>     /* bits 26:27 mirror PMIC options */
>             bios_status = (bios_status >> 26) & 3;
> 
>             if ((bios_status == 1) || (bios_status == 3))
>                 *bytcr = true;
>             else
>                 dev_info(dev, "BYT-CR not detected\n");
> 
> > 
> > Here is the relevant part from the ACPI DSDT table:
> > 
> >    Name (_ADR, Zero)  // _ADR: Address
> >    Name (_HID, "80860F28" /* Intel SST Audio DSP */)  // _HID: Hardware ID
> >    Name (_CID, "80860F28" /* Intel SST Audio DSP */)  // _CID: Compatible ID
> >    Name (_DDN, "Intel(R) Low Power Audio Controller - 80860F28")  // _DDN: DOS Device Name
> >    Name (_SUB, "80867270")  // _SUB: Subsystem ID
> >    Name (_UID, One)  // _UID: Unique ID
> > 
> >    Name (RBUF, ResourceTemplate ()
> >    {
> >        Memory32Fixed (ReadWrite,
> >            0x12345678,         // Address Base
> >            0x00200000,         // Address Length
> >            _Y08)
> >        Memory32Fixed (ReadWrite,
> >            0xFE830000,         // Address Base
> >            0x00001000,         // Address Length
> >            _Y09)
> >        Memory32Fixed (ReadWrite,
> >            0x55AA55AA,         // Address Base
> >            0x00200000,         // Address Length
> >            _Y0A)
> >        Interrupt (ResourceConsumer, Level, ActiveLow, Exclusive, ,, )
> >        {
> >            0x0000001D,
> >        }
> >    })
> > 
> > Unlike many of the other DSDT dumps I've looked at, there is only one
> > interrupt listed. Full ACPI DSDT table is at [1].
> > 
> > Since there is no IRQ at index 5, platform_get_irq will return -ENXIO.
> > Couldn't we fall back to index 0 in this case? I would say that if the
> > seemingly "correct" IRQ at index 5 does not even exist, we still have
> > a better chance of picking the right one if we try the one at index 0.
> > Or we could check the number of interrupts that are actually available.
> > 
> > The other option would be some kind of DMI-based quirk, but personally
> > I would prefer to avoid that.. (In my opinion, there is way too much
> > device specific code with the quirks etc already...)
> > 
> > Or do you have any other suggestions?
> > 
> > Thanks,
> > Stephan
> > 
> > [1]: https://github.com/me176c-dev/me176c-acpi/blob/f48c78c11b0819b899f988407b6ece3d8c2cca71/dsdt.dsl#L3989-L4035
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