On Tue, Oct 13, 2009 at 11:45 PM, Michael Ellerman
<mich...@ellerman.id.au> 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 <mich...@ellerman.id.au>
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.
> ---
> arch/powerpc/Kconfig | 13 ++++++++++++
> arch/powerpc/include/asm/irq.h | 3 ++
> arch/powerpc/kernel/irq.c | 40 ++++++++++++++++++++++++++++++++------
> arch/powerpc/kernel/ppc_ksyms.c | 1 -
> arch/powerpc/kernel/setup_64.c | 5 ----
> 5 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
> CPU. Generally saying Y is safe, although some problems have been
> reported with SMP Power Macintoshes with this option enabled.
>
> +config SPARSE_IRQ
> + bool "Support sparse irq numbering"
> + default y
> + help
> + This enables support for sparse irqs. This is useful for distro
> + kernels that want to define a high CONFIG_NR_CPUS value but still
> + want to have low kernel memory footprint on smaller machines.
> +
> + ( Sparse IRQs can also be beneficial on NUMA boxes, as they spread
> + out the irq_desc[] array in a more NUMA-friendly way. )
> +
> + If you don't know what to do here, say Y.
> +
> config NUMA
> bool "NUMA support"
> depends on PPC64
> diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
> 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;
> /* Number of irqs reserved for the legacy controller */
> #define NUM_ISA_INTERRUPTS 16
>
> +/* Same thing, used by the generic IRQ code */
> +#define NR_IRQS_LEGACY NUM_ISA_INTERRUPTS
> +
> /* This type is the placeholder for a hardware interrupt number. It has to
> * be big enough to enclose whatever representation is used by a given
> * 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);
> #endif /* CONFIG_PPC32 */
>
> #ifdef CONFIG_PPC64
> +
> +#ifndef CONFIG_SPARSE_IRQ
> EXPORT_SYMBOL(irq_desc);
> +#endif
>
> int distribute_irqs = 1;
>
> @@ -613,8 +616,16 @@ void irq_set_virq_count(unsigned int count)
> static int irq_setup_virq(struct irq_host *host, unsigned int virq,
> irq_hw_number_t hwirq)
> {
> + struct irq_desc *desc;
> +
> + desc = irq_to_desc_alloc_node(virq, 0);
> + if (!desc) {
> + pr_debug("irq: -> allocating desc failed\n");
> + goto error;
> + }
> +
> /* Clear IRQ_NOREQUEST flag */
> - irq_to_desc(virq)->status &= ~IRQ_NOREQUEST;
> + desc->status &= ~IRQ_NOREQUEST;
>
> /* map it */
> smp_wmb();
> @@ -623,11 +634,14 @@ static int irq_setup_virq(struct irq_host *host,
> unsigned int virq,
>
> if (host->ops->map(host, virq, hwirq)) {
> pr_debug("irq: -> mapping failed, freeing\n");
> - irq_free_virt(virq, 1);
> - return -1;
> + goto error;
> }
>
> return 0;
> +
> +error:
> + irq_free_virt(virq, 1);
> + return -1;
> }
>
> unsigned int irq_create_direct_mapping(struct irq_host *host)
> @@ -1008,12 +1022,24 @@ void irq_free_virt(unsigned int virq, unsigned int
> count)
> spin_unlock_irqrestore(&irq_big_lock, flags);
> }
>
> -void irq_early_init(void)
> +int arch_early_irq_init(void)
> {
> - unsigned int i;
> + struct irq_desc *desc;
> + int i;
>
> - for (i = 0; i < NR_IRQS; i++)
> - irq_to_desc(i)->status |= IRQ_NOREQUEST;
> + for (i = 0; i < NR_IRQS; i++) {
> + desc = irq_to_desc(i);
> + if (desc)
> + desc->status |= IRQ_NOREQUEST;
> + }
> +
> + return 0;
> +}
> +
> +int arch_init_chip_data(struct irq_desc *desc, int node)
> +{
> + desc->status |= IRQ_NOREQUEST;
> + return 0;
> }
>
> /* We need to create the radix trees late */
> diff --git a/arch/powerpc/kernel/ppc_ksyms.c b/arch/powerpc/kernel/ppc_ksyms.c
> 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);
>
> #ifdef CONFIG_PPC32
> EXPORT_SYMBOL(timer_interrupt);
> -EXPORT_SYMBOL(irq_desc);
> EXPORT_SYMBOL(tb_ticks_per_jiffy);
> EXPORT_SYMBOL(cacheable_memcpy);
> EXPORT_SYMBOL(cacheable_memzero);
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> 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)
> */
> initialize_cache_info();
>
> - /*
> - * Initialize irq remapping subsystem
> - */
> - irq_early_init();
> -
> #ifdef CONFIG_PPC_RTAS
> /*
> * Initialize RTAS if available
> --
> 1.6.2.1
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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