GIET-VM / XCU Driver

The xcu_driver.c​ and xcu_driver.h​ files define the XCU driver.

The vci_xcu component is an extended interrupt controller, available in the SoCLib components library, and supporting three types of interrupts:

• HWI : Hardware Interrupts (from hardware peripherals)
• PTI : Programmable Timer Interrupts (contained in the XCU component)
• WTI : Write Trigered Interrupts (from software, or from a PIC controller)

The GIET-VM uses three 32 entries interrupt vectors (one interrupt vector for each interrupt type).

The XCU component is a replicated peripheral: it must exist one XCU per cluster, and each one can contain several channels (one channel per output IRQ).

The number of XICU channels must be larger or equal to (NB_PROCS_MAX*IRQ_PER_PROCESSOR), even if the GIET-VM uses only one channel per processor (index = IRQ_PER_PROCESSOR * lpid).

The virtual base address of the segment associated to the component is:

vbase = SEG_XCU_BASE + cluster_xy * PERI_CLUSTER_INCREMENT

The SEG_XCU_BASE and PERI_CLUSTER_INCREMENT values must be defined in the hard_config.h file.

The addressable registers map is defined here​.

Access Functions

void _xcu_set_mask( unsigned int cluster_xy, unsigned int channel, unsigned int mask, unsigned int irq_type )

This function set the mask register for all IRQs of a given type.

• cluster_xy : cluster coordinates.
• channel : XCU channel (output IRQ index).
• mask : mask value : All '1' bits are set / all '0' bits are not modified.
• irq_type : IRQ type.

void _xcu_get_index( unsigned int cluster_xy, unsigned int channel, unsigned int * index, unsigned int * irq_type )

• cluster_xy : cluster coordinates.
• channel : XCU channel (output IRQ index).
• index : pointer on the index buffer.
• irq_type : pointer on the IRQ type buffer.

This function returns the index and the type of the highest priority active interrupt with the following priorities: PTI > HWI > WTI.

void _xcu_send_wti( unsigned int cluster_xy, unsigned int wti_index, unsigned int wdata )

This function writes a 32 bits word in a WTI mailbox.

• cluster_xy : cluster coordinates.
• wti_index : mailbox index.
• wdata : written value.

void _xcu_get_wti_value( unsigned int cluster_xy, unsigned int wti_index, unsigned int * value )

This function returns the value contained in a WTI mailbox. The corresponding WTI is acknowledged.

• cluster_xy : cluster coordinates.
• wti_index : mailbox index.
• value : pointer on the destination buffer.

void _xcu_get_wti_address( unsigned int wti_index, unsigned int * address )

This function returns the physical address (32 LSB bits) of the WTI mailbox identified by its index. There is no access to a specific XCU component in a specific cluster.

• wti_index : WTI index.
• address : pointer on the destination buffer.

void _xcu_timer_start( unsigned int cluster_xy, unsigned int pti_index, unsigned int period )

This function activates a timer contained in XCU by writing in the proper register the period value.

• cluster_xy : cluster coordinates.
• pti_index : mailbox index.
• period : period value.

void _xcu_timer_stop( unsigned int cluster_xy, unsigned int pti_index )

This function desactivates a timer in XCU component by writing in the proper register.

• cluster_xy : cluster coordinates.
• pti_index : mailbox index.

void _xcu_timer_reset_irq( unsigned int cluster_xy, unsigned int pti_index )

This function acknowlegge a timer interrupt in XCU component by reading in the proper XCU register. It is used by both the isr_switch() for a system timer, or by the _isr_timer() for an user timer.

• cluster_xy : cluster coordinates.
• pti_index : mailbox index.

void _xcu_timer_reset_cpt( unsigned int cluster_xy, unsigned int pti_index )

This function resets a timer counter. To do so, it read in the TIMER_PERIOD register, and rewrite the same value in the same register, what causes the count to restart. This function is called during a context switch (user or preemptive).

• cluster_xy : cluster coordinates.
• pti_index : mailbox index.