On 2015/3/19 4:07, Ard Biesheuvel wrote: > 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 agree. If user pass "acpi=force", I think it means ACPI only, so if ACPI fails, we can just not going to boot the system. > > 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 I prefer Catalin's suggestion, just not to unflatten the device tree, what do you think? If it is ok, I will add a fix patch on top of this patch set. Thanks Hanjun > > >>> - 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 > > . > -- 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