On 18 March 2015 at 12:35, Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote:
> On Wed, Mar 11, 2015 at 12:39:34PM +0000, Hanjun Guo wrote:
>> From: Al Stone <al.stone@xxxxxxxxxx>
>>
>> This implements the following policy to decide whether ACPI should
>> be used to boot the system:
>> - acpi=off: ACPI will not be used to boot the system, even if there is
>> no alternative available (e.g., device tree is empty)
>> - acpi=force: only ACPI will be used to boot the system; if that fails,
>> there will be no fallback to alternative methods (such as device tree)
>
> I think this comment is stale. acpi=force enables ACPI and tries to
> init the ACPI tables without even checking DT, but it does fall back to
> DT if ACPI table init fails (by disabling ACPI and unflattening the
> FDT).
>
> Am I wrong ?
>
No, you're right. But I would suggest that we fix the code, not the comment.
I think we are all in agreement on the policy, we only need to make
disable_acpi() conditional on whether acpi_param_force is set
>> - otherwise, ACPI will be used as a fallback if the device tree turns out
>> to lack a platform description; the heuristic to decide this is whether
>> /chosen is the only node present at depth 1
>>
>> CC: Catalin Marinas <catalin.marinas@xxxxxxx>
>> CC: Will Deacon <will.deacon@xxxxxxx>
>> CC: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
>> Acked-by: Olof Johansson <olof@xxxxxxxxx>
>> Acked-by: Grant Likely <grant.likely@xxxxxxxxxx>
>> Tested-by: Timur Tabi <timur@xxxxxxxxxxxxxx>
>> Signed-off-by: Al Stone <al.stone@xxxxxxxxxx>
>> Signed-off-by: Graeme Gregory <graeme.gregory@xxxxxxxxxx>
>> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>> ---
>> Documentation/kernel-parameters.txt | 3 ++-
>> arch/arm64/include/asm/acpi.h | 7 +++++
>> arch/arm64/kernel/acpi.c | 52 +++++++++++++++++++++++++++++++++----
>> 3 files changed, 56 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index bfcb1a6..d6c35a7 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -165,7 +165,7 @@ multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
>> bytes respectively. Such letter suffixes can also be entirely omitted.
>>
>>
>> - acpi= [HW,ACPI,X86]
>> + acpi= [HW,ACPI,X86,ARM64]
>> Advanced Configuration and Power Interface
>> Format: { force | off | strict | noirq | rsdt }
>> force -- enable ACPI if default was off
>> @@ -175,6 +175,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>> strictly ACPI specification compliant.
>> rsdt -- prefer RSDT over (default) XSDT
>> copy_dsdt -- copy DSDT to memory
>> + For ARM64, ONLY "acpi=off" or "acpi=force" are available
>>
>> See also Documentation/power/runtime_pm.txt, pci=noacpi
>>
>> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>> index 40e0924..c5a9b97 100644
>> --- a/arch/arm64/include/asm/acpi.h
>> +++ b/arch/arm64/include/asm/acpi.h
>> @@ -39,6 +39,13 @@ static inline void disable_acpi(void)
>> acpi_noirq = 1;
>> }
>>
>> +static inline void enable_acpi(void)
>> +{
>> + acpi_disabled = 0;
>> + acpi_pci_disabled = 0;
>> + acpi_noirq = 0;
>> +}
>> +
>> /*
>> * It's used from ACPI core in kdump to boot UP system with SMP kernel,
>> * with this check the ACPI core will not override the CPU index
>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>> index 7abac24..2269e30 100644
>> --- a/arch/arm64/kernel/acpi.c
>> +++ b/arch/arm64/kernel/acpi.c
>> @@ -22,15 +22,49 @@
>> #include <linux/irq.h>
>> #include <linux/irqdomain.h>
>> #include <linux/memblock.h>
>> +#include <linux/of_fdt.h>
>> #include <linux/smp.h>
>>
>> -int acpi_noirq; /* skip ACPI IRQ initialization */
>> -int acpi_disabled;
>> +int acpi_noirq = 1; /* skip ACPI IRQ initialization */
>> +int acpi_disabled = 1;
>> EXPORT_SYMBOL(acpi_disabled);
>>
>> -int acpi_pci_disabled; /* skip ACPI PCI scan and IRQ initialization */
>> +int acpi_pci_disabled = 1; /* skip ACPI PCI scan and IRQ initialization */
>> EXPORT_SYMBOL(acpi_pci_disabled);
>>
>> +static bool param_acpi_off __initdata;
>> +static bool param_acpi_force __initdata;
>> +
>> +static int __init parse_acpi(char *arg)
>> +{
>> + if (!arg)
>> + return -EINVAL;
>> +
>> + /* "acpi=off" disables both ACPI table parsing and interpreter */
>> + if (strcmp(arg, "off") == 0)
>> + param_acpi_off = true;
>> + else if (strcmp(arg, "force") == 0) /* force ACPI to be enabled */
>> + param_acpi_force = true;
>> + else
>> + return -EINVAL; /* Core will print when we return error */
>> +
>> + return 0;
>> +}
>> +early_param("acpi", parse_acpi);
>> +
>> +static int __init dt_scan_depth1_nodes(unsigned long node,
>> + const char *uname, int depth,
>> + void *data)
>> +{
>> + /*
>> + * Return 1 as soon as we encounter a node at depth 1 that is
>> + * not the /chosen node.
>> + */
>> + if (depth == 1 && (strcmp(uname, "chosen") != 0))
>> + return 1;
>> + return 0;
>> +}
>> +
>> /*
>> * __acpi_map_table() will be called before page_init(), so early_ioremap()
>> * or early_memremap() should be called here to for ACPI table mapping.
>> @@ -83,10 +117,18 @@ static int __init acpi_parse_fadt(struct acpi_table_header *table)
>> */
>> void __init acpi_boot_table_init(void)
>> {
>> - /* If acpi_disabled, bail out */
>> - if (acpi_disabled)
>> + /*
>> + * Enable ACPI instead of device tree unless
>> + * - ACPI has been disabled explicitly (acpi=off), or
>> + * - the device tree is not empty (it has more than just a /chosen node)
>> + * and ACPI has not been force enabled (acpi=force)
>> + */
>> + if (param_acpi_off ||
>> + (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
>> return;
>>
>> + enable_acpi();
>> +
>> /* Initialize the ACPI boot-time table parser. */
>> if (acpi_table_init()) {
>> disable_acpi();
>> --
>> 1.9.1
>>
>>
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
