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sfc: Rework IRQ enable/disable

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There are many problems with the current efx_stop_interrupts() and
efx_start_interrupts():

1. On Siena, it is unsafe to disable the master IRQ enable bit
(DRV_INT_EN_KER) while any IRQ sources are enabled.

2. On EF10 there is no master IRQ enable bit, so we cannot expect to
defer IRQs without tearing down event queues.  (Though I don't think
we will need to keep any event queues around while the device is down,
as we do for VFDI on Siena.)

3. synchronize_irq() only waits for a running IRQ handler to finish,
not for any propagation through IRQ controllers.  Therefore an IRQ may
still be received and handled after efx_stop_interrupts() returns.
IRQ handlers can then race with channel reallocation.

To fix this:

a. Introduce a software IRQ enable flag.  So long as this is clear,
IRQ handlers will only acknowledge IRQs and not touch the channel
structures.

b. Define a new struct efx_msi_context as the context for MSIs.  This
is never reallocated and is sufficient to find the software enable
flag and the channel structure.  It also includes the channel/IRQ
name, which was previously separated out as it must also not be
reallocated.

c. Split efx_{start,stop}_interrupts() into
efx_{,soft_}_{enable,disable}_interrupts().  The 'soft' functions
don't touch the hardware master enable flag (if it exists) and don't
reinitialise or tear down channels with the keep_eventq flag set.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
This commit is contained in:
Ben Hutchings 2012-10-05 23:35:41 +01:00
parent 514bedbc3a
commit d829118705
4 changed files with 119 additions and 66 deletions
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24
drivers/net/ethernet/sfc/net_driver.h
View file

@ -419,6 +419,21 @@ struct efx_channel {
struct efx_tx_queue tx_queue[EFX_TXQ_TYPES];
};
/**
* struct efx_msi_context - Context for each MSI
* @efx: The associated NIC
* @index: Index of the channel/IRQ
* @name: Name of the channel/IRQ
*
* Unlike &struct efx_channel, this is never reallocated and is always
* safe for the IRQ handler to access.
*/
struct efx_msi_context {
struct efx_nic *efx;
unsigned int index;
char name[IFNAMSIZ + 6];
};
/**
* struct efx_channel_type - distinguishes traffic and extra channels
* @handle_no_channel: Handle failure to allocate an extra channel
@ -669,7 +684,6 @@ struct vfdi_status;
* @pci_dev: The PCI device
* @type: Controller type attributes
* @legacy_irq: IRQ number
* @legacy_irq_enabled: Are IRQs enabled on NIC (INT_EN_KER register)?
* @workqueue: Workqueue for port reconfigures and the HW monitor.
* Work items do not hold and must not acquire RTNL.
* @workqueue_name: Name of workqueue
@ -686,7 +700,7 @@ struct vfdi_status;
* @tx_queue: TX DMA queues
* @rx_queue: RX DMA queues
* @channel: Channels
* @channel_name: Names for channels and their IRQs
* @msi_context: Context for each MSI
* @extra_channel_types: Types of extra (non-traffic) channels that
* should be allocated for this NIC
* @rxq_entries: Size of receive queues requested by user.
@ -709,6 +723,8 @@ struct vfdi_status;
* @rx_scatter: Scatter mode enabled for receives
* @int_error_count: Number of internal errors seen recently
* @int_error_expire: Time at which error count will be expired
* @irq_soft_enabled: Are IRQs soft-enabled? If not, IRQ handler will
* acknowledge but do nothing else.
* @irq_status: Interrupt status buffer
* @irq_zero_count: Number of legacy IRQs seen with queue flags == 0
* @irq_level: IRQ level/index for IRQs not triggered by an event queue
@ -786,7 +802,6 @@ struct efx_nic {
unsigned int port_num;
const struct efx_nic_type *type;
int legacy_irq;
bool legacy_irq_enabled;
bool eeh_disabled_legacy_irq;
struct workqueue_struct *workqueue;
char workqueue_name[16];
@ -804,7 +819,7 @@ struct efx_nic {
unsigned long reset_pending;
struct efx_channel *channel[EFX_MAX_CHANNELS];
char channel_name[EFX_MAX_CHANNELS][IFNAMSIZ + 6];
struct efx_msi_context msi_context[EFX_MAX_CHANNELS];
const struct efx_channel_type *
extra_channel_type[EFX_MAX_EXTRA_CHANNELS];
@ -835,6 +850,7 @@ struct efx_nic {
unsigned int_error_count;
unsigned long int_error_expire;
bool irq_soft_enabled;
struct efx_buffer irq_status;
unsigned irq_zero_count;
unsigned irq_level;