Re: [PATCH 2/3] irq: Add hw continuous IRQs map to virtual continuous IRQs support

Michael Ellerman
2013-03-05T02:23:52Z

On Tue, Jan 15, 2013 at 03:38:55PM +0800, Mike Qiu wrote:
> Adding a function irq_create_mapping_many() which can associate
> multiple MSIs to a continous irq mapping.
>
> This is needed to enable multiple MSI support for pSeries.
>
> Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
> ---
> include/linux/irq.h | 2 +
> include/linux/irqdomain.h | 3 ++
> kernel/irq/irqdomain.c | 61 +++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 66 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/irq.h b/include/linux/irq.h
> index 60ef45b..e00a7ec 100644
> --- a/include/linux/irq.h
> +++ b/include/linux/irq.h
> @@ -592,6 +592,8 @@ int __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node,
> #define irq_alloc_desc_from(from, node) \
> irq_alloc_descs(-1, from, 1, node)
>
> +#define irq_alloc_desc_n(nevc, node) \
> + irq_alloc_descs(-1, 0, nevc, node)

This has been superseeded by irq_alloc_descs_from(), which is the right
way to do it.

> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index 0d5b17b..831dded 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -168,6 +168,9 @@ extern int irq_create_strict_mappings(struct irq_domain *domain,
> unsigned int irq_base,
> irq_hw_number_t hwirq_base, int count);
>
> +extern int irq_create_mapping_many(struct irq_domain *domain,
> + irq_hw_number_t hwirq_base, int count);
> +
> static inline int irq_create_identity_mapping(struct irq_domain *host,
> irq_hw_number_t hwirq)
> {
> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> index 96f3a1d..38648e6 100644
> --- a/kernel/irq/irqdomain.c
> +++ b/kernel/irq/irqdomain.c
> @@ -636,6 +636,67 @@ int irq_create_strict_mappings(struct irq_domain *domain, unsigned int irq_base,
> }
> EXPORT_SYMBOL_GPL(irq_create_strict_mappings);
>
> +/**
> + * irq_create_mapping_many - Map a range of hw IRQs to a range of virtual IRQs
> + * @domain: domain owning the interrupt range
> + * @hwirq_base: beginning of continuous hardware IRQ range
> + * @count: Number of interrupts to map

For multiple-MSI the allocated interrupt numbers must be a power-of-2,
and must be naturally aligned. I don't /think/ that's a requirement for
the virtual numbers, but it's probably best that we do it anyway.

So this API needs to specify that it will give you back a power-of-2
block that is naturally aligned - otherwise you can't use it for MSI.

> + * This routine is used for allocating and mapping a range of hardware
> + * irqs to virtual IRQs where the virtual irq numbers are not at pre-defined
> + * locations.

This comment doesn't make sense to me.

> + *
> + * Greater than 0 is returned upon success, while any failure to establish a
> + * static mapping is treated as an error.
> + */
> +int irq_create_mapping_many(struct irq_domain *domain,
> + irq_hw_number_t hwirq_base, int count)
> +{
> + int ret, irq_base;
> + int virq, i;
> +
> + pr_debug("irq_create_mapping(0x%p, 0x%lx)\n", domain, hwirq_base);

I'd like to see this whole function rewritten to reduce the duplication
vs irq_create_mapping(). I don't see any reason why this can't be the
core routine, and irq_create_mapping() becomes a caller of it, passing a
count of 1 ?

> + /* Look for default domain if nececssary */
> + if (!domain)
> + domain = irq_default_domain;
> + if (!domain) {
> + pr_warn("irq_create_mapping called for NULL domain, hwirq=%lx\n"
> + , hwirq_base);
> + WARN_ON(1);
> + return 0;
> + }
> + pr_debug("-> using domain @%p\n", domain);
> +
> + /* For IRQ_DOMAIN_MAP_LEGACY, get the first virtual interrupt number */
> + if (domain->revmap_type == IRQ_DOMAIN_MAP_LEGACY)
> + return irq_domain_legacy_revmap(domain, hwirq_base);

The above doesn't work.

> + /* Check if mapping already exists */
> + for (i = 0; i < count; i++) {
> + virq = irq_find_mapping(domain, hwirq_base+i);
> + if (virq) {
> + pr_debug("existing mapping on virq %d,"
> + " now dispose it first\n", virq);
> + irq_dispose_mapping(virq);

You might have just disposed of someone elses mapping, we shouldn't do
that. It should be an error to the caller.

cheers