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Date: Thu, 19 Mar 2015 10:04:55 +0000
From: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: "hanjun.guo@...aro.org" <hanjun.guo@...aro.org>,
Catalin Marinas <Catalin.Marinas@....com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Will Deacon <Will.Deacon@....com>,
Olof Johansson <olof@...om.net>,
"grant.likely@...aro.org" <grant.likely@...aro.org>,
Arnd Bergmann <arnd@...db.de>,
Mark Rutland <Mark.Rutland@....com>,
"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
Sudeep Holla <Sudeep.Holla@....com>,
"jcm@...hat.com" <jcm@...hat.com>,
Marc Zyngier <Marc.Zyngier@....com>,
Mark Brown <broonie@...nel.org>,
Robert Richter <rric@...nel.org>,
Timur Tabi <timur@...eaurora.org>,
Ashwin Chaugule <ashwinc@...eaurora.org>,
"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
Al Stone <al.stone@...aro.org>
Subject: Re: [PATCH v10 08/21] ARM64 / ACPI: Introduce early_param "acpi=" to
enable/disable ACPI
On Wed, Mar 18, 2015 at 08:07:09PM +0000, Ard Biesheuvel wrote:
> On 18 March 2015 at 12:35, Lorenzo Pieralisi <lorenzo.pieralisi@....com> wrote:
> > On Wed, Mar 11, 2015 at 12:39:34PM +0000, Hanjun Guo wrote:
> >> From: Al Stone <al.stone@...aro.org>
> >>
> >> 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.
So would I. I flagged this up on the comment since I was not able to follow
the thread on arm64 acpi=force and thought I was missing something.
> 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
Either this or Catalin's fix, in actual terms the end result should be
the same on arm64, leaving acpi_disabled will save us some pointless
parsing IMO.
Nit: "acpi" kernel parameter description defines
"force -- enable ACPI if default was off"
which is not what we do on arm64 if we leave ACPI disabled when
acpi=force and ACPI fails to init.
I do not think we should care, if anyone disagrees manifest yourselves.
Lorenzo
>
>
> >> - 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@....com>
> >> CC: Will Deacon <will.deacon@....com>
> >> CC: Rafael J. Wysocki <rjw@...ysocki.net>
> >> Acked-by: Olof Johansson <olof@...om.net>
> >> Acked-by: Grant Likely <grant.likely@...aro.org>
> >> Tested-by: Timur Tabi <timur@...eaurora.org>
> >> Signed-off-by: Al Stone <al.stone@...aro.org>
> >> Signed-off-by: Graeme Gregory <graeme.gregory@...aro.org>
> >> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> >> ---
> >> 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
> >>
> >>
>
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