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Date:	Thu, 19 Mar 2015 10:30:09 +0800
From:	Hanjun Guo <guohanjun@...wei.com>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	Hanjun Guo <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 2015/3/19 4:07, 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.

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@....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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