Re: [coreboot] ASRock E350M1/AMD Persimmon: Linux 3.2.x complains about `ACPI: Invalid PBLK length [0]`

[Paul Menzel]

Dear coreboot folks,

Am Sonntag, den 20.01.2013, 23:46 +0100 schrieb Paul Menzel:
> Am Sonntag, den 20.01.2013, 11:50 +0100 schrieb Paul Menzel:
> > in Debian Sid/unstable with Linux 3.2.35 looking at the Linux messages
> > in the output of `dmesg` I see
> >     ACPI: Invalid PBLK length [0]
> >
> > which results from
> >     $ more src/mainboard/asrock/e350m1/dsdt.asl
> >     […]
> >     	/*
> >     	 * Processor Object
> >     	 *
> >     	 */
> >     	Scope (\_PR) {		/* define processor scope */
> >     		Processor(
> >     			C000,		/* name space name, align with BLDCFG_PROCESSOR_SCOPE_NAME[01] */
> >     			0,		/* Unique number for this processor */
> >     			0x810,		/* PBLK system I/O address !hardcoded! */
> >     			0x06		/* PBLKLEN for boot processor */
> >     			) {
> >     		}
> >
> >     		Processor(
> >     			C001,		/* name space name */
> >     			1,		/* Unique number for this processor */
> >     			0x810,		/* PBLK system I/O address !hardcoded! */
> >     			0x00		/* PBLKLEN for boot processor */
> >     			) {
> >     		}
> >     		Processor(
> >     			C002,		/* name space name */
> >     			2,		/* Unique number for this processor */
> >     			0x810,		/* PBLK system I/O address !hardcoded! */
> >     			0x00		/* PBLKLEN for boot processor */
> >     			) {
> >     		}
> >     		Processor(
> >     			C003,		/* name space name */
> >     			3,		/* Unique number for this processor */
> >     			0x810,		/* PBLK system I/O address !hardcoded! */
> >     			0x00		/* PBLKLEN for boot processor */
> >     			) {
> >     		}
> >     	} /* End _PR scope */
> >     […]
> >
> > Is that an error in the Linux ACPI code? According to Colin King’s
> > comment (25) to the Launchpad report [1], the ACPI specification allows
> > it to be set to 0.
> >     »Section 18.5.93 of the ACPI specification states that the
> >     PBlockLength is the length of the processor register block, in
> >     bytes and is either 0 (for no P_BLK) or 6.« [2]
> >
> > So the DSDT seems to be valid. Before I report that to the Linux ACPI
> > folks, could you please tell me if I am missing something?
>
> Looking at the Linux code in `drivers/acpi/processor_driver.c` only 6
> seems to be allowed [2].
>     static int acpi_processor_get_info(struct acpi_device *device)
>     {
>     […]
>     	/*
>     	 * On some boxes several processors use the same processor bus id.
>     	 * But they are located in different scope. For example:
>     	 * \_SB.SCK0.CPU0
>     	 * \_SB.SCK1.CPU0
>     	 * Rename the processor device bus id. And the new bus id will be
>     	 * generated as the following format:
>     	 * CPU+CPU ID.
>     	 */
>     	sprintf(acpi_device_bid(device), "CPU%X", pr->id);
>     	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Processor [%d:%d]\n", pr->id,
>     			  pr->acpi_id));
>
>     	if (!object.processor.pblk_address)
>     		ACPI_DEBUG_PRINT((ACPI_DB_INFO, "No PBLK (NULL address)\n"));
>     	else if (object.processor.pblk_length != 6)
>     		printk(KERN_ERR PREFIX "Invalid PBLK length [%d]\n",
>     			    object.processor.pblk_length);
>     	else {
>     		pr->throttling.address = object.processor.pblk_address;
>     		pr->throttling.duty_offset = acpi_gbl_FADT.duty_offset;
>     		pr->throttling.duty_width = acpi_gbl_FADT.duty_width;
>
>     		pr->pblk = object.processor.pblk_address;
>
>     		/*
>     		 * We don't care about error returns - we just try to mark
>     		 * these reserved so that nobody else is confused into thinking
>     		 * that this region might be unused..
>     		 *
>     		 * (In particular, allocating the IO range for Cardbus)
>     		 */
>     		request_region(pr->throttling.address, 6, "ACPI CPU throttle");
>     	}
>     […]
>     }
>
> So I am going to submit a bug report to the Linux ACPI folks tomorrow.

Well, reading the ACPI specification [4], 0 is only allowed, if there is
no PBlockAddress.

18.5.93 Processor (Declare Processor)

[…]

PBlockAddress provides the system I/O address for the processors
        register block. Each processor can supply a different such
        address. PBlockLength is the length of the processor register
        block, in bytes and is either 0 (for no P_BLK) or 6. With one
        exception, all processors are required to have the same
        PBlockLength. The exception is that the boot processor can have
        a non-zero PBlockLength when all other processors have a zero
        PBlockLength. It is valid for every processor to have a
        PBlockLength of 0.

Thanks,

Paul
> > [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/197267
> > [2] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/197267/comments/25
>
> [3] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=driver...

[4] http://acpi.info/DOWNLOADS/ACPIspec40a.pdf