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Date: Tue, 20 Feb 2018 17:27:18 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
"H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
"the arch/x86 maintainers" <x86@...nel.org>,
Eric Biederman <ebiederm@...ssion.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
Juergen Gross <jgross@...e.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] ACPI / x86: boot: Not all platforms require acpi_reduced_hw_init()
On Tue, Feb 20, 2018 at 5:03 PM, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> Some platforms might take care of legacy devices on theirs own. Due to this,
> export acpi_reduced_hw_init() and put it into struct x86_init_acpi.
IMO this completely doesn't explain what really happens here.
You basically want to provide your own versions of
x86_init.timers.timer_init, x86_init.irqs.pre_vector_init and
legacy_pic on some HW-reduced platforms AFAICS, so you make it
possible for the platform to provide its own variant of
acpi_reduced_hw_init().
I would say something like this:
"Some ACPI hawdware-reduced platforms need to initialize certain
devices defined by the ACPI hardware specification even though in
principle those devices should not be present in an ACPI
hawdware-reduced platform. To allow that to happen, make it possible
to override the generic x86_init callbacks and provide a custom
legacy_pic value, add a new ->reduced_hw_early_init() callback to
struct x86_init_acpi and make acpi_reduced_hw_init() use it."
And I would retain acpi_reduced_hw_init(), but ->
> While doing this, rename acpi_reduced_hw_init() to
> acpi_reduced_hw_early_init() to show the stage at which it's called.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>
> - re-done based on patches from Juergen Gross
> - supposed to go via tip tree (x86/boot branch)
> - tested on ASuS T100ta (HW reduced) and Intel Broxton based platforms
>
> arch/x86/include/asm/acpi.h | 4 ++++
> arch/x86/include/asm/x86_init.h | 2 ++
> arch/x86/kernel/acpi/boot.c | 21 ++++++++++-----------
> arch/x86/kernel/x86_init.c | 2 ++
> 4 files changed, 18 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
> index 6609dd7289b5..f3f86be35fc5 100644
> --- a/arch/x86/include/asm/acpi.h
> +++ b/arch/x86/include/asm/acpi.h
> @@ -140,6 +140,8 @@ static inline u64 acpi_arch_get_root_pointer(void)
> return x86_init.acpi.get_root_pointer();
> }
>
> +void acpi_reduced_hw_early_init(void);
> +
> #else /* !CONFIG_ACPI */
>
> #define acpi_lapic 0
> @@ -149,6 +151,8 @@ static inline void acpi_noirq_set(void) { }
> static inline void acpi_disable_pci(void) { }
> static inline void disable_acpi(void) { }
>
> +static inline void acpi_reduced_hw_early_init(void) { }
> +
> #endif /* !CONFIG_ACPI */
>
> #define ARCH_HAS_POWER_INIT 1
> diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
> index 5ffa116ddb08..199e15bd3ec5 100644
> --- a/arch/x86/include/asm/x86_init.h
> +++ b/arch/x86/include/asm/x86_init.h
> @@ -133,9 +133,11 @@ struct x86_hyper_init {
> /**
> * struct x86_init_acpi - x86 ACPI init functions
> * @get_root_pointer: get RSDP address
> + * @reduced_hw_early_init: hardware reduced platform early init
> */
> struct x86_init_acpi {
> u64 (*get_root_pointer)(void);
> + void (*reduced_hw_early_init)(void);
> };
>
> /**
> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> index d3deae23e584..02acf1c58d3a 100644
> --- a/arch/x86/kernel/acpi/boot.c
> +++ b/arch/x86/kernel/acpi/boot.c
> @@ -1378,17 +1378,15 @@ static int __init dmi_ignore_irq0_timer_override(const struct dmi_system_id *d)
> *
> * We initialize the Hardware-reduced ACPI model here:
> */
> -static void __init acpi_reduced_hw_init(void)
> +void __init acpi_reduced_hw_early_init(void)
-> I would call this acpi_generic_reduced_hw_init() and ->>
> {
> - if (acpi_gbl_reduced_hardware) {
> - /*
> - * Override x86_init functions and bypass legacy pic
> - * in Hardware-reduced ACPI mode
> - */
> - x86_init.timers.timer_init = x86_init_noop;
> - x86_init.irqs.pre_vector_init = x86_init_noop;
> - legacy_pic = &null_legacy_pic;
> - }
> + /*
> + * Override x86_init functions and bypass legacy pic
> + * in Hardware-reduced ACPI mode.
> + */
> + x86_init.timers.timer_init = x86_init_noop;
> + x86_init.irqs.pre_vector_init = x86_init_noop;
> + legacy_pic = &null_legacy_pic;
> }
>
> /*
> @@ -1593,7 +1591,8 @@ int __init early_acpi_boot_init(void)
> /*
> * Hardware-reduced ACPI mode initialization:
> */
> - acpi_reduced_hw_init();
> + if (acpi_gbl_reduced_hardware)
> + x86_init.acpi.reduced_hw_early_init();
->> I would put the two lines above into acpi_reduced_hw_init().
>
> return 0;
> }
> diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
> index 32c288ebf870..8fd63640e764 100644
> --- a/arch/x86/kernel/x86_init.c
> +++ b/arch/x86/kernel/x86_init.c
> @@ -8,6 +8,7 @@
> #include <linux/export.h>
> #include <linux/pci.h>
>
> +#include <asm/acpi.h>
> #include <asm/bios_ebda.h>
> #include <asm/paravirt.h>
> #include <asm/pci_x86.h>
> @@ -95,6 +96,7 @@ struct x86_init_ops x86_init __initdata = {
>
> .acpi = {
> .get_root_pointer = u64_x86_init_noop,
> + .reduced_hw_early_init = acpi_reduced_hw_early_init,
> },
> };
>
> --
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