Re: [PATCH 6/6] powerpc: Enable sparse irq_descs on powerpc

From: Grant Likely <hidden>
Date: 2009-10-14 18:46:16

On Tue, Oct 13, 2009 at 11:45 PM, Michael Ellerman
[off-list ref] wrote:

Defining CONFIG_SPARSE_IRQ enables generic code that gets rid of the
static irq_desc array, and replaces it with an array of pointers to
irq_descs.

It also allows node local allocation of irq_descs, however we
currently don't have the information available to do that, so we just
allocate them on all on node 0.

Signed-off-by: Michael Ellerman <redacted>

Why not make sparse IRQs manditory for all platforms?  Is there a
performance concern with doing so?  From a maintenance perspective,
I'd rather see IRQ descs manged in one way only to keep the code
simple.

Cheers,
g.

---
=A0arch/powerpc/Kconfig =A0 =A0 =A0 =A0 =A0 =A0| =A0 13 ++++++++++++
=A0arch/powerpc/include/asm/irq.h =A0| =A0 =A03 ++
=A0arch/powerpc/kernel/irq.c =A0 =A0 =A0 | =A0 40 +++++++++++++++++++++++=

+++++++++------

quoted hunk ↗ jump to hunk

=A0arch/powerpc/kernel/ppc_ksyms.c | =A0 =A01 -
=A0arch/powerpc/kernel/setup_64.c =A0| =A0 =A05 ----
=A05 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2230e75..825d889 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -388,6 +388,19 @@ config IRQ_ALL_CPUS

=A0 =A0 =A0 =A0 =A0CPU. =A0Generally saying Y is safe, although some prob=

lems have been

=A0 =A0 =A0 =A0 =A0reported with SMP Power Macintoshes with this option e=

nabled.

+config SPARSE_IRQ
+ =A0 =A0 =A0 bool "Support sparse irq numbering"
+ =A0 =A0 =A0 default y
+ =A0 =A0 =A0 help
+ =A0 =A0 =A0 =A0 This enables support for sparse irqs. This is useful fo=

r distro

+ =A0 =A0 =A0 =A0 kernels that want to define a high CONFIG_NR_CPUS value=

 but still

+ =A0 =A0 =A0 =A0 want to have low kernel memory footprint on smaller mac=

hines.

+
+ =A0 =A0 =A0 =A0 ( Sparse IRQs can also be beneficial on NUMA boxes, as =

they spread

+ =A0 =A0 =A0 =A0 =A0 out the irq_desc[] array in a more NUMA-friendly wa=

y. )

quoted hunk ↗ jump to hunk

+
+ =A0 =A0 =A0 =A0 If you don't know what to do here, say Y.
+
=A0config NUMA
=A0 =A0 =A0 =A0bool "NUMA support"
=A0 =A0 =A0 =A0depends on PPC64

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/ir=

q.h

quoted hunk ↗ jump to hunk

index 03dc28c..c85a32f 100644

--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h

@@ -38,6 +38,9 @@ extern atomic_t ppc_n_lost_interrupts;

=A0/* Number of irqs reserved for the legacy controller */
=A0#define NUM_ISA_INTERRUPTS =A0 =A0 16

+/* Same thing, used by the generic IRQ code */
+#define NR_IRQS_LEGACY =A0 =A0 =A0 =A0 NUM_ISA_INTERRUPTS
+
=A0/* This type is the placeholder for a hardware interrupt number. It ha=

s to

quoted hunk ↗ jump to hunk

=A0* be big enough to enclose whatever representation is used by a given
=A0* platform.

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 63e27d5..eba5392 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c

@@ -85,7 +85,10 @@ extern int tau_interrupts(int);

=A0#endif /* CONFIG_PPC32 */

=A0#ifdef CONFIG_PPC64
+
+#ifndef CONFIG_SPARSE_IRQ
=A0EXPORT_SYMBOL(irq_desc);
+#endif

=A0int distribute_irqs =3D 1;

@@ -613,8 +616,16 @@ void irq_set_virq_count(unsigned int count)

=A0static int irq_setup_virq(struct irq_host *host, unsigned int virq,
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0irq_hw_number_t hw=

irq)

=A0{
+ =A0 =A0 =A0 struct irq_desc *desc;
+
+ =A0 =A0 =A0 desc =3D irq_to_desc_alloc_node(virq, 0);
+ =A0 =A0 =A0 if (!desc) {
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 pr_debug("irq: -> allocating desc failed\n"=

);

quoted hunk ↗ jump to hunk

+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 goto error;
+ =A0 =A0 =A0 }
+
=A0 =A0 =A0 =A0/* Clear IRQ_NOREQUEST flag */
- =A0 =A0 =A0 irq_to_desc(virq)->status &=3D ~IRQ_NOREQUEST;
+ =A0 =A0 =A0 desc->status &=3D ~IRQ_NOREQUEST;

=A0 =A0 =A0 =A0/* map it */
=A0 =A0 =A0 =A0smp_wmb();

@@ -623,11 +634,14 @@ static int irq_setup_virq(struct irq_host *host, un=

signed int virq,

=A0 =A0 =A0 =A0if (host->ops->map(host, virq, hwirq)) {
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0pr_debug("irq: -> mapping failed, freeing\=

n");

quoted hunk ↗ jump to hunk

- =A0 =A0 =A0 =A0 =A0 =A0 =A0 irq_free_virt(virq, 1);
- =A0 =A0 =A0 =A0 =A0 =A0 =A0 return -1;
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 goto error;
=A0 =A0 =A0 =A0}

=A0 =A0 =A0 =A0return 0;
+
+error:
+ =A0 =A0 =A0 irq_free_virt(virq, 1);
+ =A0 =A0 =A0 return -1;
=A0}

=A0unsigned int irq_create_direct_mapping(struct irq_host *host)

@@ -1008,12 +1022,24 @@ void irq_free_virt(unsigned int virq, unsigned in=

t count)

=A0 =A0 =A0 =A0spin_unlock_irqrestore(&irq_big_lock, flags);
=A0}

-void irq_early_init(void)
+int arch_early_irq_init(void)
=A0{
- =A0 =A0 =A0 unsigned int i;
+ =A0 =A0 =A0 struct irq_desc *desc;
+ =A0 =A0 =A0 int i;

- =A0 =A0 =A0 for (i =3D 0; i < NR_IRQS; i++)
- =A0 =A0 =A0 =A0 =A0 =A0 =A0 irq_to_desc(i)->status |=3D IRQ_NOREQUEST;
+ =A0 =A0 =A0 for (i =3D 0; i < NR_IRQS; i++) {
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 desc =3D irq_to_desc(i);
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (desc)
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 desc->status |=3D IRQ_NOREQ=

UEST;

quoted hunk ↗ jump to hunk

+ =A0 =A0 =A0 }
+
+ =A0 =A0 =A0 return 0;
+}
+
+int arch_init_chip_data(struct irq_desc *desc, int node)
+{
+ =A0 =A0 =A0 desc->status |=3D IRQ_NOREQUEST;
+ =A0 =A0 =A0 return 0;
=A0}

=A0/* We need to create the radix trees late */

diff --git a/arch/powerpc/kernel/ppc_ksyms.c b/arch/powerpc/kernel/ppc_ks=

yms.c

quoted hunk ↗ jump to hunk

index c8b27bb..07115d6 100644

--- a/arch/powerpc/kernel/ppc_ksyms.c
+++ b/arch/powerpc/kernel/ppc_ksyms.c

@@ -162,7 +162,6 @@ EXPORT_SYMBOL(screen_info);

=A0#ifdef CONFIG_PPC32
=A0EXPORT_SYMBOL(timer_interrupt);
-EXPORT_SYMBOL(irq_desc);
=A0EXPORT_SYMBOL(tb_ticks_per_jiffy);
=A0EXPORT_SYMBOL(cacheable_memcpy);
=A0EXPORT_SYMBOL(cacheable_memzero);

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_6=

4.c

quoted hunk ↗ jump to hunk

index 797ea95..8e5ec92 100644

--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c

@@ -357,11 +357,6 @@ void __init setup_system(void)

=A0 =A0 =A0 =A0 */
=A0 =A0 =A0 =A0initialize_cache_info();

- =A0 =A0 =A0 /*
- =A0 =A0 =A0 =A0* Initialize irq remapping subsystem
- =A0 =A0 =A0 =A0*/
- =A0 =A0 =A0 irq_early_init();
-
=A0#ifdef CONFIG_PPC_RTAS
=A0 =A0 =A0 =A0/*
=A0 =A0 =A0 =A0 * Initialize RTAS if available
--
1.6.2.1

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--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

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