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[PATCH v3 0/7] Early ACPI probing infrastructure

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  [PATCH v3 0/7] Early ACPI probing infrastructure Marc Zyngier <marc.zyngier@arm.com> - 2015-09-28 17:00 +0200
    [PATCH v3 2/7] irqchip/acpi: Add probing infrastructure for ACPI-based irqchips Marc Zyngier <marc.zyngier@arm.com> - 2015-09-28 17:00 +0200
      Re: [PATCH v3 2/7] irqchip/acpi: Add probing infrastructure for  ACPI-based irqchips Catalin Marinas <catalin.marinas@arm.com> - 2015-09-29 12:30 +0200
      Re: [PATCH v3 2/7] irqchip/acpi: Add probing infrastructure for ACPI-based  irqchips Hanjun Guo <hanjun.guo@linaro.org> - 2015-09-29 16:50 +0200
    [PATCH v3 6/7] clocksource/arm_arch_timer: Convert to ACPI probing Marc Zyngier <marc.zyngier@arm.com> - 2015-09-28 17:00 +0200
      Re: [PATCH v3 6/7] clocksource/arm_arch_timer: Convert to ACPI  probing Catalin Marinas <catalin.marinas@arm.com> - 2015-09-29 12:30 +0200
    Re: [PATCH v3 0/7] Early ACPI probing infrastructure "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-29 00:20 +0200
      Re: [PATCH v3 0/7] Early ACPI probing infrastructure Thomas Gleixner <tglx@linutronix.de> - 2015-09-30 12:50 +0200
        Re: [PATCH v3 0/7] Early ACPI probing infrastructure "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-10-05 15:10 +0200
    Re: [PATCH v3 0/7] Early ACPI probing infrastructure Hanjun Guo <hanjun.guo@linaro.org> - 2015-09-29 17:30 +0200

#1234234 — [PATCH v3 0/7] Early ACPI probing infrastructure

IRQ controllers and timers are the two types of device the kernel
requires before being able to use the device driver model.

The Device Tree infrastructure makes it very easy to make these
discoverable by the rest of the kernel. For example, each interrupt
controller driver has at least one entry like this:

IRQCHIP_DECLARE(gic_400, "arm,gic-400", gic_of_init);

which says: if you find a node having "arm,gic-400" as a compatible
string in the device tree, then call gic_of_init with this node as a
parameter. The probing itself is done by the OF layer when the
architecture code calls of_irq_init() (usually via irqchip_init).

This has a number of benefits:

- The irqchip code is self-contained. No architecture specific entry
point, no exposed symbols. Just a standard interface.

- The low-level architecture code doesn't have to know about which
interrupt controller is present. It just calls into the firmware
interface (of_irq_init) which is going to sort things out.

Similar infrastructure is provided for the timers/clock sources. Note
that this is not a replacement for the device model, but acts as a
probing infrastructure for things that are required too early for the
device infrastructure to be available.

What I'm aiming for is to introduce the same level of abstraction for
ACPI, or at least for the few bits that are required before a full blown
ACPI/device model can be used. For this, I introduce something vaguely
similar:

IRQCHIP_ACPI_DECLARE(gic_v2, ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR,
		     gic_validate_dist, ACPI_MADT_GIC_VERSION_V2,
		     gic_v2_acpi_init);

which says: if you find a ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR entry in
MADT (implied by the macro), and that entry is of type
ACPI_MADT_GIC_VERSION_V2 (as checked by gic_validate_dist), then call
gic_v2_acpi_init with the entry as a parameter. A bit more convoluted,
but still without any special entry point.

The various interrupt controller drivers can then implement the above,
and the arch code can use a firmware-specific call to get the probing
done, still oblivious to what interrupt controller is being used. It
also makes the adaptation of a DT driver to ACPI easier.

It turns out that providing such a probing infrastructure is rather
easy, and provides a much deserved cleanup in both the arch code, the
GIC driver, and the architected timer driver. An additional (and very
much optional) patch renames files and symbols to make it obvious that
the infrastructure is not just for DT anymore.

I'm sure there is some more code to be deleted, and one can only
wonder why this wasn't done before the arm64 code was initially merged
(the diffstat says it all...).

Patches are against Rafael's bleeding-edge branch, and a branch is
available at

git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git acpi/device-probing-v3

* From v2:
  - Addressed Rafael's comments (title for patch #1, macro/field names)
  - New config symbols for clocksources
  - Additional and optional last patch to get rid of the apparent
    dependency between the probing infrastructure and DT.

* From the initial version:
  - Make the infrastructure more DT like by providing an
    acpi_probe_entry array per "device type" (one for irqchips, one
    for clocksources). This means that entries can depend on any ACPI
    static table.
  - Use some cpp magic to reduce the amount of code added to an
    absolute minimum.
  - Rebased on v4.3-rc1

Marc Zyngier (7):
  acpi: Add early device probing infrastructure
  irqchip/acpi: Add probing infrastructure for ACPI-based irqchips
  irqchip/gic: Convert the GIC driver to ACPI probing
  clocksource/acpi: Add probing infrastructure for ACPI-based
    clocksources
  clocksource: Add new CLKSRC_{PROBE,ACPI} config symbols
  clocksource/arm_arch_timer: Convert to ACPI probing
  clocksource: cosmetic: Drop OF 'dependency' from symbols

 arch/arm/kernel/time.c                             |  2 +-
 arch/arm/mach-omap2/timer.c                        |  4 +-
 arch/arm/mach-rockchip/rockchip.c                  |  2 +-
 arch/arm/mach-shmobile/setup-r8a7779.c             |  2 +-
 arch/arm/mach-shmobile/setup-rcar-gen2.c           |  2 +-
 arch/arm/mach-spear/spear13xx.c                    |  2 +-
 arch/arm/mach-sunxi/sunxi.c                        |  2 +-
 arch/arm/mach-u300/core.c                          |  2 +-
 arch/arm/mach-ux500/timer.c                        |  2 +-
 arch/arm/mach-zynq/common.c                        |  2 +-
 arch/arm64/include/asm/acpi.h                      |  1 -
 arch/arm64/include/asm/irq.h                       | 13 ----
 arch/arm64/kernel/acpi.c                           | 25 --------
 arch/arm64/kernel/time.c                           |  8 +--
 arch/microblaze/kernel/setup.c                     |  2 +-
 arch/mips/pistachio/time.c                         |  2 +-
 arch/mips/ralink/clk.c                             |  2 +-
 arch/nios2/kernel/time.c                           |  2 +-
 arch/xtensa/kernel/time.c                          |  2 +-
 drivers/acpi/scan.c                                | 39 ++++++++++++
 drivers/clocksource/Kconfig                        |  9 +++
 drivers/clocksource/Makefile                       |  2 +-
 drivers/clocksource/arm_arch_timer.c               | 10 +---
 .../clocksource/{clksrc-of.c => clksrc-probe.c}    |  6 +-
 drivers/irqchip/irq-gic.c                          | 69 +++++++++++-----------
 drivers/irqchip/irqchip.c                          |  5 +-
 include/asm-generic/vmlinux.lds.h                  | 12 ++++
 include/linux/acpi.h                               | 66 +++++++++++++++++++++
 include/linux/acpi_irq.h                           | 10 ----
 include/linux/clocksource.h                        | 13 ++--
 include/linux/irqchip.h                            | 17 ++++++
 include/linux/irqchip/arm-gic-acpi.h               | 31 ----------
 32 files changed, 209 insertions(+), 159 deletions(-)
 rename drivers/clocksource/{clksrc-of.c => clksrc-probe.c} (91%)
 delete mode 100644 include/linux/acpi_irq.h
 delete mode 100644 include/linux/irqchip/arm-gic-acpi.h

-- 
2.1.4

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#1234235 — [PATCH v3 2/7] irqchip/acpi: Add probing infrastructure for ACPI-based irqchips

DT enjoys a rather nice probing infrastructure for irqchips, while
ACPI is so far stuck into a very distant past.

This patch introduces a declarative API, allowing irqchips to be
self-contained and be called when a particular entry is matched
in the MADT table.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm64/include/asm/irq.h      | 11 -----------
 drivers/irqchip/irqchip.c         |  8 +++++---
 include/asm-generic/vmlinux.lds.h |  1 +
 include/linux/acpi_irq.h          | 10 ----------
 include/linux/irqchip.h           | 17 +++++++++++++++++
 5 files changed, 23 insertions(+), 24 deletions(-)
 delete mode 100644 include/linux/acpi_irq.h

diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index bbb251b..1a1037a 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -10,15 +10,4 @@ struct pt_regs;
 extern void migrate_irqs(void);
 extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
 
-static inline void acpi_irq_init(void)
-{
-	/*
-	 * Hardcode ACPI IRQ chip initialization to GICv2 for now.
-	 * Proper irqchip infrastructure will be implemented along with
-	 * incoming  GICv2m|GICv3|ITS bits.
-	 */
-	acpi_gic_init();
-}
-#define acpi_irq_init acpi_irq_init
-
 #endif
diff --git a/drivers/irqchip/irqchip.c b/drivers/irqchip/irqchip.c
index afd1af3..1ee773e 100644
--- a/drivers/irqchip/irqchip.c
+++ b/drivers/irqchip/irqchip.c
@@ -8,7 +8,7 @@
  * warranty of any kind, whether express or implied.
  */
 
-#include <linux/acpi_irq.h>
+#include <linux/acpi.h>
 #include <linux/init.h>
 #include <linux/of_irq.h>
 #include <linux/irqchip.h>
@@ -27,6 +27,8 @@ extern struct of_device_id __irqchip_of_table[];
 void __init irqchip_init(void)
 {
 	of_irq_init(__irqchip_of_table);
-
-	acpi_irq_init();
+#if defined(CONFIG_ARM64) && defined(CONFIG_ACPI)
+	acpi_gic_init();	/* Temporary hack */
+#endif
+	acpi_probe_device_table(irqchip);
 }
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index efd7ed1..cd836cd 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -524,6 +524,7 @@
 	CPUIDLE_METHOD_OF_TABLES()					\
 	KERNEL_DTB()							\
 	IRQCHIP_OF_MATCH_TABLE()					\
+	ACPI_PROBE_TABLE(irqchip)					\
 	EARLYCON_TABLE()						\
 	EARLYCON_OF_TABLES()
 
diff --git a/include/linux/acpi_irq.h b/include/linux/acpi_irq.h
deleted file mode 100644
index f10c872..0000000
--- a/include/linux/acpi_irq.h
+++ /dev/null
@@ -1,10 +0,0 @@
-#ifndef _LINUX_ACPI_IRQ_H
-#define _LINUX_ACPI_IRQ_H
-
-#include <linux/irq.h>
-
-#ifndef acpi_irq_init
-static inline void acpi_irq_init(void) { }
-#endif
-
-#endif /* _LINUX_ACPI_IRQ_H */
diff --git a/include/linux/irqchip.h b/include/linux/irqchip.h
index 6388873..89c34b2 100644
--- a/include/linux/irqchip.h
+++ b/include/linux/irqchip.h
@@ -11,6 +11,7 @@
 #ifndef _LINUX_IRQCHIP_H
 #define _LINUX_IRQCHIP_H
 
+#include <linux/acpi.h>
 #include <linux/of.h>
 
 /*
@@ -25,6 +26,22 @@
  */
 #define IRQCHIP_DECLARE(name, compat, fn) OF_DECLARE_2(irqchip, name, compat, fn)
 
+/*
+ * This macro must be used by the different irqchip drivers to declare
+ * the association between their version and their initialization function.
+ *
+ * @name: name that must be unique accross all IRQCHIP_ACPI_DECLARE of the
+ * same file.
+ * @subtable: Subtable to be identified in MADT
+ * @validate: Function to be called on that subtable to check its validity.
+ *            Can be NULL.
+ * @data: data to be checked by the validate function.
+ * @fn: initialization function
+ */
+#define IRQCHIP_ACPI_DECLARE(name, subtable, validate, data, fn)	\
+	ACPI_DECLARE_PROBE_ENTRY(irqchip, name, ACPI_SIG_MADT, 		\
+				 subtable, validate, data, fn)
+
 #ifdef CONFIG_IRQCHIP
 void irqchip_init(void);
 #else
-- 
2.1.4

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#1234948 — Re: [PATCH v3 2/7] irqchip/acpi: Add probing infrastructure for ACPI-based irqchips

On Mon, Sep 28, 2015 at 03:49:13PM +0100, Marc Zyngier wrote:
> DT enjoys a rather nice probing infrastructure for irqchips, while
> ACPI is so far stuck into a very distant past.
> 
> This patch introduces a declarative API, allowing irqchips to be
> self-contained and be called when a particular entry is matched
> in the MADT table.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/arm64/include/asm/irq.h      | 11 -----------
>  drivers/irqchip/irqchip.c         |  8 +++++---
>  include/asm-generic/vmlinux.lds.h |  1 +
>  include/linux/acpi_irq.h          | 10 ----------
>  include/linux/irqchip.h           | 17 +++++++++++++++++
>  5 files changed, 23 insertions(+), 24 deletions(-)
>  delete mode 100644 include/linux/acpi_irq.h

For the arm64 part:

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
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#1235182 — Re: [PATCH v3 2/7] irqchip/acpi: Add probing infrastructure for ACPI-based irqchips

On 09/28/2015 10:49 PM, Marc Zyngier wrote:
> DT enjoys a rather nice probing infrastructure for irqchips, while
> ACPI is so far stuck into a very distant past.
>
> This patch introduces a declarative API, allowing irqchips to be
> self-contained and be called when a particular entry is matched
> in the MADT table.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>

Thanks
Hanjun
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#1234238 — [PATCH v3 6/7] clocksource/arm_arch_timer: Convert to ACPI probing

It is now absolutely trivial to convert the arch timer driver to
use ACPI probing, just like its DT counterpart.

Let's enjoy another crapectomy.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm64/kernel/time.c             |  6 ------
 drivers/clocksource/Kconfig          |  1 +
 drivers/clocksource/arm_arch_timer.c | 10 +---------
 include/linux/clocksource.h          |  6 ------
 4 files changed, 2 insertions(+), 21 deletions(-)

diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
index 149151f..819a105 100644
--- a/arch/arm64/kernel/time.c
+++ b/arch/arm64/kernel/time.c
@@ -71,12 +71,6 @@ void __init time_init(void)
 
 	tick_setup_hrtimer_broadcast();
 
-	/*
-	 * Since ACPI or FDT will only one be available in the system,
-	 * we can use acpi_generic_timer_init() here safely
-	 */
-	acpi_generic_timer_init();
-
 	arch_timer_rate = arch_timer_get_rate();
 	if (!arch_timer_rate)
 		panic("Unable to initialise architected timer.\n");
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index fefedf1..1a9c5dc 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -131,6 +131,7 @@ config CLKSRC_STM32
 config ARM_ARCH_TIMER
 	bool
 	select CLKSRC_OF if OF
+	select CLKSRC_ACPI if ACPI
 
 config ARM_ARCH_TIMER_EVTSTREAM
 	bool "Support for ARM architected timer event stream generation"
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index d6e3e49..c64d543 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -864,13 +864,5 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table)
 	arch_timer_init();
 	return 0;
 }
-
-/* Initialize all the generic timers presented in GTDT */
-void __init acpi_generic_timer_init(void)
-{
-	if (acpi_disabled)
-		return;
-
-	acpi_table_parse(ACPI_SIG_GTDT, arch_timer_acpi_init);
-}
+CLOCKSOURCE_ACPI_DECLARE(arch_timer, ACPI_SIG_GTDT, arch_timer_acpi_init);
 #endif
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 6eab6ab..116645f 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -252,12 +252,6 @@ extern void clocksource_of_init(void);
 static inline void clocksource_of_init(void) {}
 #endif
 
-#ifdef CONFIG_ACPI
-void acpi_generic_timer_init(void);
-#else
-static inline void acpi_generic_timer_init(void) { }
-#endif
-
 #define CLOCKSOURCE_ACPI_DECLARE(name, table_id, fn)		\
 	ACPI_DECLARE_PROBE_ENTRY(clksrc, name, table_id, 0, NULL, 0, fn)
 
-- 
2.1.4

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#1234942 — Re: [PATCH v3 6/7] clocksource/arm_arch_timer: Convert to ACPI probing

On Mon, Sep 28, 2015 at 03:49:17PM +0100, Marc Zyngier wrote:
> It is now absolutely trivial to convert the arch timer driver to
> use ACPI probing, just like its DT counterpart.
> 
> Let's enjoy another crapectomy.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
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#1234546

On Monday, September 28, 2015 03:49:11 PM Marc Zyngier wrote:
> IRQ controllers and timers are the two types of device the kernel
> requires before being able to use the device driver model.
> 
> The Device Tree infrastructure makes it very easy to make these
> discoverable by the rest of the kernel. For example, each interrupt
> controller driver has at least one entry like this:
> 
> IRQCHIP_DECLARE(gic_400, "arm,gic-400", gic_of_init);
> 
> which says: if you find a node having "arm,gic-400" as a compatible
> string in the device tree, then call gic_of_init with this node as a
> parameter. The probing itself is done by the OF layer when the
> architecture code calls of_irq_init() (usually via irqchip_init).
> 
> This has a number of benefits:
> 
> - The irqchip code is self-contained. No architecture specific entry
> point, no exposed symbols. Just a standard interface.
> 
> - The low-level architecture code doesn't have to know about which
> interrupt controller is present. It just calls into the firmware
> interface (of_irq_init) which is going to sort things out.
> 
> Similar infrastructure is provided for the timers/clock sources. Note
> that this is not a replacement for the device model, but acts as a
> probing infrastructure for things that are required too early for the
> device infrastructure to be available.
> 
> What I'm aiming for is to introduce the same level of abstraction for
> ACPI, or at least for the few bits that are required before a full blown
> ACPI/device model can be used. For this, I introduce something vaguely
> similar:
> 
> IRQCHIP_ACPI_DECLARE(gic_v2, ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR,
> 		     gic_validate_dist, ACPI_MADT_GIC_VERSION_V2,
> 		     gic_v2_acpi_init);
> 
> which says: if you find a ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR entry in
> MADT (implied by the macro), and that entry is of type
> ACPI_MADT_GIC_VERSION_V2 (as checked by gic_validate_dist), then call
> gic_v2_acpi_init with the entry as a parameter. A bit more convoluted,
> but still without any special entry point.
> 
> The various interrupt controller drivers can then implement the above,
> and the arch code can use a firmware-specific call to get the probing
> done, still oblivious to what interrupt controller is being used. It
> also makes the adaptation of a DT driver to ACPI easier.
> 
> It turns out that providing such a probing infrastructure is rather
> easy, and provides a much deserved cleanup in both the arch code, the
> GIC driver, and the architected timer driver. An additional (and very
> much optional) patch renames files and symbols to make it obvious that
> the infrastructure is not just for DT anymore.
> 
> I'm sure there is some more code to be deleted, and one can only
> wonder why this wasn't done before the arm64 code was initially merged
> (the diffstat says it all...).
> 
> Patches are against Rafael's bleeding-edge branch, and a branch is
> available at
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git acpi/device-probing-v3
> 
> * From v2:
>   - Addressed Rafael's comments (title for patch #1, macro/field names)
>   - New config symbols for clocksources
>   - Additional and optional last patch to get rid of the apparent
>     dependency between the probing infrastructure and DT.
> 
> * From the initial version:
>   - Make the infrastructure more DT like by providing an
>     acpi_probe_entry array per "device type" (one for irqchips, one
>     for clocksources). This means that entries can depend on any ACPI
>     static table.
>   - Use some cpp magic to reduce the amount of code added to an
>     absolute minimum.
>   - Rebased on v4.3-rc1
> 
> Marc Zyngier (7):
>   acpi: Add early device probing infrastructure
>   irqchip/acpi: Add probing infrastructure for ACPI-based irqchips
>   irqchip/gic: Convert the GIC driver to ACPI probing
>   clocksource/acpi: Add probing infrastructure for ACPI-based
>     clocksources
>   clocksource: Add new CLKSRC_{PROBE,ACPI} config symbols
>   clocksource/arm_arch_timer: Convert to ACPI probing
>   clocksource: cosmetic: Drop OF 'dependency' from symbols

If you want me to apply this series, ACKs are needed for patches [3-7/7].

They are fine by me, but I'd also like to hear from the other maintainers.

Thanks,
Rafael

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#1236136

On Tue, 29 Sep 2015, Rafael J. Wysocki wrote:
> If you want me to apply this series, ACKs are needed for patches [3-7/7].
> 
> They are fine by me, but I'd also like to hear from the other maintainers.

Acked-by: Thomas Gleixner <tglx@linutronix.de>


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#1239527

On Wednesday, September 30, 2015 12:44:29 PM Thomas Gleixner wrote:
> On Tue, 29 Sep 2015, Rafael J. Wysocki wrote:
> > If you want me to apply this series, ACKs are needed for patches [3-7/7].
> > 
> > They are fine by me, but I'd also like to hear from the other maintainers.
> 
> Acked-by: Thomas Gleixner <tglx@linutronix.de>

Thanks Thomas!

Series applied.

Rafael

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#1235264

On 09/28/2015 10:49 PM, Marc Zyngier wrote:
> IRQ controllers and timers are the two types of device the kernel
> requires before being able to use the device driver model.
>
> The Device Tree infrastructure makes it very easy to make these
> discoverable by the rest of the kernel. For example, each interrupt
> controller driver has at least one entry like this:
>
> IRQCHIP_DECLARE(gic_400, "arm,gic-400", gic_of_init);
>
> which says: if you find a node having "arm,gic-400" as a compatible
> string in the device tree, then call gic_of_init with this node as a
> parameter. The probing itself is done by the OF layer when the
> architecture code calls of_irq_init() (usually via irqchip_init).
>
> This has a number of benefits:
>
> - The irqchip code is self-contained. No architecture specific entry
> point, no exposed symbols. Just a standard interface.
>
> - The low-level architecture code doesn't have to know about which
> interrupt controller is present. It just calls into the firmware
> interface (of_irq_init) which is going to sort things out.
>
> Similar infrastructure is provided for the timers/clock sources. Note
> that this is not a replacement for the device model, but acts as a
> probing infrastructure for things that are required too early for the
> device infrastructure to be available.
>
> What I'm aiming for is to introduce the same level of abstraction for
> ACPI, or at least for the few bits that are required before a full blown
> ACPI/device model can be used. For this, I introduce something vaguely
> similar:
>
> IRQCHIP_ACPI_DECLARE(gic_v2, ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR,
> 		     gic_validate_dist, ACPI_MADT_GIC_VERSION_V2,
> 		     gic_v2_acpi_init);
>
> which says: if you find a ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR entry in
> MADT (implied by the macro), and that entry is of type
> ACPI_MADT_GIC_VERSION_V2 (as checked by gic_validate_dist), then call
> gic_v2_acpi_init with the entry as a parameter. A bit more convoluted,
> but still without any special entry point.
>
> The various interrupt controller drivers can then implement the above,
> and the arch code can use a firmware-specific call to get the probing
> done, still oblivious to what interrupt controller is being used. It
> also makes the adaptation of a DT driver to ACPI easier.
>
> It turns out that providing such a probing infrastructure is rather
> easy, and provides a much deserved cleanup in both the arch code, the
> GIC driver, and the architected timer driver. An additional (and very
> much optional) patch renames files and symbols to make it obvious that
> the infrastructure is not just for DT anymore.
>
> I'm sure there is some more code to be deleted, and one can only
> wonder why this wasn't done before the arm64 code was initially merged
> (the diffstat says it all...).
>
> Patches are against Rafael's bleeding-edge branch, and a branch is
> available at
>
> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git acpi/device-probing-v3
>
> * From v2:
>    - Addressed Rafael's comments (title for patch #1, macro/field names)
>    - New config symbols for clocksources

I like this one most :)

>    - Additional and optional last patch to get rid of the apparent
>      dependency between the probing infrastructure and DT.
>
> * From the initial version:
>    - Make the infrastructure more DT like by providing an
>      acpi_probe_entry array per "device type" (one for irqchips, one
>      for clocksources). This means that entries can depend on any ACPI
>      static table.
>    - Use some cpp magic to reduce the amount of code added to an
>      absolute minimum.
>    - Rebased on v4.3-rc1
>
> Marc Zyngier (7):
>    acpi: Add early device probing infrastructure
>    irqchip/acpi: Add probing infrastructure for ACPI-based irqchips
>    irqchip/gic: Convert the GIC driver to ACPI probing
>    clocksource/acpi: Add probing infrastructure for ACPI-based
>      clocksources
>    clocksource: Add new CLKSRC_{PROBE,ACPI} config symbols
>    clocksource/arm_arch_timer: Convert to ACPI probing
>    clocksource: cosmetic: Drop OF 'dependency' from symbols

Tested locally on QEMU (as I'm in home so no hardware is available) and
it boots as before with GICv2 and arch timer work ok (sure with ACPI),
for this patch set:

Tested-by: Hanjun Guo <hanjun.guo@linaro.org>

Thanks
Hanjun
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