Boot and Initialization¶

Boot¶

After Power-On Reset, the core should be configured to prevent it from interacting with the I3C bus in any way.

This implementation supports 3 modes at boot:

• Active Controller Mode

• Secondary Controller Mode (Target)

• Disabled Mode

We propose the following boot sequence:

• Power-On Reset

• Device is in Disabled Mode (reset values defined at synthesis time)

• System Manager initializes itself and enables clock for the I3C Core

• System Manager initializes relevant registers of the I3C Core

• System Manager enables the desired mode of operation: Active or Secondary Controller Mode

• The device is ready for normal operation

Primary Controller Initialization¶

The following section details the initialization process on the software driver side, in compliance with the I3C HCI Specification:

• “6.1.1 Host Controller Initialization” in the PIO mode

• “6.17.1.1 Secondary Controller Initialization”

The following process is described under the assumption that the controller has undergone software- or hardware-issued reset prior to the initialization, so that all the registers and internal FSMs are in the default state.

To initialize the controller, the software is expected to perform the following steps:

1. Verify the value of the HCI_VERSION register at the I3CBase address. The controller is compliant with MIPI HCI v1.2 and therefore the HCI_VERSION should read 0x120

2. Evaluate DAT & DCT table offsets:

   • The DAT_SECTION_OFFSET register defined at I3CBase + 0x30

   • The DCT_SECTION_OFFSET register defined at I3CBase + 0x34

   • Both DAT_SECTION_OFFSET and DCT_SECTION_OFFSET contain the corresponding table offset, number of entries & table size

   • HCI spec permits to require the driver to allocate the DAT & DCT table, in which case the TABLE_OFFSET would read 0. This specific controller implementation allocates both DAT and DCT tables in the registers

3. Evaluate PIO_SECTION_OFFSET:

   • Read PIO_SECTION_OFFSET at I3CBase  + 0x3c, the section_offset field points to the PIOControl register file that contains command, transfer, response and IBI ports as well as PIO control registers

   • This specific controller implements the PIO mode capability. If it’s not supported, SECTION_OFFSET will read 0

4. Evaluate RING_HEADERS_SECTION_OFFSET, the SECTION_OFFSET should read 0x0 as this controller doesn’t support the DMA mode

5. Evaluate the HC_CAPABILITIES register at I3CBase + 0xC:

   • It stores controller capabilities such as scatter-gather, scheduled commands, combo transfers, IBI data abort, command size

6. Extended capabilities evaluation via EXT_CAPS_SECTION_OFFSET at I3CBase + 0x40

   • Evaluate the linked list of Extended Capability structures, until the end of the linked list (i.e., an instance of the EXTCAP_HEADER register with the 0x00 value in the CAP_ID field)

   • EXT_OFFSET will read 0x0 if the extended capabilities are not supported

7. Setup the threshold for the HCI queues (in the internal/private software data structures):

   • The command, data buffer and IBI status queue sizes can be obtained through the QUEUE_SIZE register at PIO_OFFSET + 0x18

   • The response queue size is defined at ALT_QUEUE_SIZE at PIO_OFFSET + 0x1C when the size of the command queue is not equal to the size of the response queue (which is the case for this host controller)

   • both are contained within PIOControl register file

8. Enable the host controller:

   • Ensure the MODE_SELECTOR field in the HC_CONTROL register is set to 0x1 (PIO mode)

   • Set the BUS_ENABLE field in the HC_CONTROL register

9. Enable controller interrupts:

   • Set fields for the status interrupts to be enabled in the INTR_STATUS_ENABLE register at I3CBase + 0x24; the following status interrupts can be set:

     • Scheduled command missed tick

     • Controller command sequence stall / timeout

     • Controller canceled transaction sequence

     • Controller internal error

   • Upon writing 1'b1, the interrupt will be reported in STATUS_REGISTER

   • Setting the fields in the INTR_SIGNAL_ENABLE register at I3CBase + 0x28 will result in not only reporting the interrupt in the STATUS_REGISTER register but will also deliver an interrupt condition to the host (interrupt trigger)

10. Enable and start PIO queues:

    • Enable PIO interrupts via PIO_INTR_STATUS_ENABLE at PIO_OFFSET + 0x20 and PIO_INTR_SIGNAL_ENABLE at PIO_OFFSET + 0x20; enabling fields in the status register will cause the interrupts to be reported via the PIO_INTR_STATUS register, additionally enabling interrupts in PIO_INTR_SIGNAL_ENABLE will cause an event for the host controller

    • Enable queues by setting the ENABLE field in the PIO_CONTROL register

    • Start PIO queues by setting the RS field in the PIO_CONTROL register

The host control will expose its register map and will await the driver to set the BUS_ENABLE bit in the HC_CONTROL register. After that, the controller will evaluate the capabilities limited by the software and initialize internal queues & resources accordingly.

Secondary Controller Initialization¶

The Secondary Controller Initialization process requires additional steps (in addition to the previous steps):

1. Evaluate the Standby Controller Mode Extended Capability structure (see Section 7.7.11):

   • Determine whether an I3C Target Transaction Interface to software is supported.

     • If this interface is supported, then discover its capabilities and configure the interface appropriately (i.e., by using its vendor-specified Extended Capability structure). Then, enable the interface using the TARGET_XACT_ENABLE field in the STBY_CR_CONTROL register (Section 7.7.11.1).

   • Determine which methods of Dynamic Address Assignment are implemented and supported by reading the STBY_CR_CAPABILITIES register (Section 7.7.11.3)

   • Determine which other CCCs need to be supported and configured, either as registers in the Standby Controller Mode Extended Capability structure, or as registers in any instances of other vendor-specific Extended Capability structures that might be defined to provide control for such CCC handling.

2. Set the BCR bits and the DCR value in the STBY_CR_DEVICE_CHAR register (Section 7.7.11.5).

3. Optionally, set the PID value in the STBY_CR_DEVICE_CHAR and STBY_CR_DEVICE_PID_LO registers (Section 7.7.11.5 and Section 7.7.11.6) if required for the Dynamic Address Assignment with the ENTDAA procedure, or if it is known that the GETPID CCC will be used by an Active Controller.

4. Configure registers to set up autonomous responses for CCCs, for those CCCs that are defined for such handling in this specification (see Section 6.17.3.1).

5. Enable Secondary Controller Interrupts:

   • In the STBY_CR_INTR_SIGNAL_ENABLE register (Section 7.7.11.8), set the mask of enabled interrupts.