Re: [PATCH v7 11/14] irqchip: ti-sci-inta: Add support for Interrupt Aggregator driver

Marc Zyngier
2019-04-29T13:11:39Z

On 20/04/2019 11:09, Lokesh Vutla wrote:
> Texas Instruments' K3 generation SoCs has an IP Interrupt Aggregator
> which is an interrupt controller that does the following:
> - Converts events to interrupts that can be understood by
> an interrupt router.
> - Allows for multiplexing of events to interrupts.
>
> Configuration of the interrupt aggregator registers can only be done by
> a system co-processor and the driver needs to send a message to this
> co processor over TISCI protocol. This patch adds support for Interrupt
> Aggregator irqdomain.
>
> Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
> ---
> Changes since v6:
> - Updated commit message.
> - Arranged header files in alphabetical order
> - Included vint_bit in struct ti_sci_inta_event_desc
> - With the above change now the chip_data is event_desc instead of vint_desc
> - No loops are used in atomic contexts.
> - Fixed locking issue while freeing parent virq
> - Fixed few other cosmetic changes.
>
> MAINTAINERS | 1 +
> drivers/irqchip/Kconfig | 11 +
> drivers/irqchip/Makefile | 1 +
> drivers/irqchip/irq-ti-sci-inta.c | 589 ++++++++++++++++++++++++++++++
> 4 files changed, 602 insertions(+)
> create mode 100644 drivers/irqchip/irq-ti-sci-inta.c
>

[...]

> +/**
> + * ti_sci_inta_alloc_irq() - Allocate an irq within INTA domain
> + * @domain: irq_domain pointer corresponding to INTA
> + * @hwirq: hwirq of the input event
> + *
> + * Note: Allocation happens in the following manner:
> + * - Find a free bit available in any of the vints available in the list.
> + * - If not found, allocate a vint from the vint pool
> + * - Attach the free bit to input hwirq.
> + * Return event_desc if all went ok else appropriate error value.
> + */
> +static struct ti_sci_inta_event_desc *ti_sci_inta_alloc_irq(struct irq_domain *domain,
> + u32 hwirq)
> +{
> + struct ti_sci_inta_irq_domain *inta = domain->host_data;
> + struct ti_sci_inta_vint_desc *vint_desc = NULL;
> + u16 free_bit;
> +
> + mutex_lock(&inta->vint_mutex);
> + list_for_each_entry(vint_desc, &inta->vint_list, list) {
> + mutex_lock(&vint_desc->event_mutex);
> + free_bit = find_first_zero_bit(vint_desc->event_map,
> + MAX_EVENTS_PER_VINT);
> + if (free_bit != MAX_EVENTS_PER_VINT) {
> + set_bit(free_bit, vint_desc->event_map);
> + mutex_unlock(&vint_desc->event_mutex);
> + mutex_unlock(&inta->vint_mutex);
> + goto alloc_event;
> + }
> + mutex_unlock(&vint_desc->event_mutex);
> + }
> + mutex_unlock(&inta->vint_mutex);
> +
> + /* No free bits available. Allocate a new vint */
> + vint_desc = ti_sci_inta_alloc_parent_irq(domain);
> + if (IS_ERR(vint_desc))
> + return ERR_PTR(PTR_ERR(vint_desc));
> +
> + mutex_lock(&vint_desc->event_mutex);
> + free_bit = find_first_zero_bit(vint_desc->event_map,
> + MAX_EVENTS_PER_VINT);
> + set_bit(free_bit, vint_desc->event_map);
> + mutex_unlock(&vint_desc->event_mutex);

This code is still quite racy: you can have two parallel allocations
failing to get a free bit in any of the already allocated vint_desc, and
then both allocating a new vint_desc. If there was only one left, one of
the allocation will fail despite having at least 63 free interrupts.

M.
--
Jazz is not dead. It just smells funny...