linux-kernel - Re: [PATCH 1/8] arm64: move acpi/dt decision earlier in boot process

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Date:	Wed, 24 Feb 2016 19:09:59 +0300
From:	Aleksey Makarov <amakarov.linux@...il.com>
To:	Matthias Brugger <matthias.bgg@...il.com>,
	Graeme Gregory <gg@...mlogic.co.uk>
Cc:	Aleksey Makarov <aleksey.makarov@...aro.org>,
	linux-acpi@...r.kernel.org, Russell King <linux@....linux.org.uk>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Christopher Covington <cov@...eaurora.org>,
	linux-serial@...r.kernel.org,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>, Al Stone <ahs3@...hat.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/8] arm64: move acpi/dt decision earlier in boot process

Hi Matthias,

Thank you for review.  The bug is fixed in the next version of the patchset.

Aleksey Makarov

On 02/23/2016 05:37 PM, Matthias Brugger wrote:
> 
> 
> On 23/02/16 14:57, Graeme Gregory wrote:
>> On Mon, Feb 22, 2016 at 04:45:17PM +0100, Matthias Brugger wrote:
>>>
>>>
>>> On 22/02/16 14:46, Aleksey Makarov wrote:
>>>> From: Leif Lindholm <leif.lindholm@...aro.org>
>>>>
>>>> In order to support selecting earlycon via either ACPI or DT, move
>>>> the decision on whether to attempt ACPI configuration into the
>>>> early_param handling. Then make acpi_boot_table_init() bail out if
>>>> acpi_disabled.
>>>>
>>>> Signed-off-by: Leif Lindholm <leif.lindholm@...aro.org>
>>>> ---
>>>>   arch/arm64/kernel/acpi.c | 54 ++++++++++++++++++++++++++----------------------
>>>>   1 file changed, 29 insertions(+), 25 deletions(-)
>>>>
>>>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>>>> index d1ce8e2..7a944f7 100644
>>>> --- a/arch/arm64/kernel/acpi.c
>>>> +++ b/arch/arm64/kernel/acpi.c
>>>> @@ -44,6 +44,19 @@ EXPORT_SYMBOL(acpi_pci_disabled);
>>>>   static bool param_acpi_off __initdata;
>>>>   static bool param_acpi_force __initdata;
>>>>
>>>> +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;
>>>> +}
>>>> +
>>>>   static int __init parse_acpi(char *arg)
>>>>   {
>>>>       if (!arg)
>>>> @@ -57,23 +70,27 @@ static int __init parse_acpi(char *arg)
>>>>       else
>>>>           return -EINVAL;    /* Core will print when we return error */
> 
> If argument of parse_acpi is neither "off" nor "force" we return with -EINVAL here. Actually parse_acpi will be only called if we pass "acpi=" as kernel parameter. Therefor we can get rid of "acpi=off" as this is the _new_ standard. IMHO we should introduce "acpi=on" if we really want to change the standard behavior.
> 
>>>>
>>>> -    return 0;
>>>> -}
>>>> -early_param("acpi", parse_acpi);
>>>> +    /*
>>>> +     * 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 0;
> 
> Or param_acpi_off is true or param_acpi_force is true, the depth of the DT has no influence.
> 
>>>>
>>>> -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.
>>>> +     * ACPI is disabled at this point. Enable it in order to parse
>>>> +     * the ACPI tables and carry out sanity checks
>>>>        */
>>>> -    if (depth == 1 && (strcmp(uname, "chosen") != 0))
>>>> -        return 1;
>>>> +    enable_acpi();
>>>> +
>>>
>>> So we only enable ACPI if we pass acpi=force as kernel parameter?
>>> I'm not sure if this is what you wanted to do.
>>>
>>
>> The current preference from ARM64 maintainers was that is both ACPI
>> tables and a DT were presented then DT should take precedence.
>>
>> With no DT provided the code should use ACPI.
> 
> From my understanding in this patch that can never happen.
> 
> On which version is this set based on?
> I'm looking on v4.5-rc5 ATM.
> 
> Regards,
> Matthias
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