Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 7/19/2024
Public
Document Table of Contents

5.4.7.3.2. Command Queueing Error Recovery

The figure below shows an example command queueing error recovery procedure required to get the host controller and a device recovered from error state and prepare for following operations.

Figure 152. Command Queueing Error Recovery Procedure
Notes:
  • The SD host controller always replies to the halt request by setting halt acknowledge. Software needs to wait for acknowledgement before running generic operation error recovery. The acknowledge is signaled after an unpredictable amount of time – the time required to finish any pending operation. The acknowledge is set when command and data paths report their status (whether they successfully completed or were interrupted by an error).
  • The discard/task clear is required for the task interrupted by an error.

The command queueing reuses the protection mechanisms built into the SD host controller. It also adds an automatic error detection for the R1 device response.

Following is a full list of errors that can be detected by the command queueing:

  • R1 response error
  • Command errors (Index/CRC/End Bit/Timeout)
  • Data transfer errors (CRC/End Bit/Timeout)
  • DMA error
  • Manager interface error

Once any of these errors is detected, the internal logic stops, reports the error type, and waits for the command queueing error recovery procedure.

Command queueing can send CMD13 SQS (Send Queue Status) to a device during the data transaction. If this feature is enabled (that is, CQRS16.CQSSCBC > 0) and a data transaction is in progress, the controller sends CMD13 SQS concurrently to the data transaction and reports possible CMD13 SQS error in the auto command error status registers (SRS15[4:1]).

SD/eMMC host controller might report current limit error but this error is command queueing task agnostic and will not interrupt transactions. This error is application-specific and, therefore, should be classified as a non-recoverable error. Software reaction must be adequate and follow the application assumptions.

SD/eMMC host controller does not use the response error check mechanism when command queueing is enabled.

Software can either poll the status registers or rely on the interrupts generated by the host controller. If an error occurs, it must raise a system interrupt, software enables the required interrupt status registers before task submission. The interrupt generation is configured by the following registers:

  • Error Status Enable (SRS13[31:16])
  • Error Signal Enable (SRS14[31:16])
  • AXI Error Response (HRS03[19:16], HRS03[11:8])
  • Response Error Detected Status Enable (CQRS05[2])
  • Response Error Detected Signal Enable (CQRS06[2])

The following table describes the command queueing error cases.

Table 222.  Command Queueing Error Cases
Operation Event Consequence
Read task descriptor before CMD44 (task queueing) Master error Halt and report task ID in response mode error
Read task descriptor before CMD46 / CMD47 (task execution) Master error Halt and report task ID in data transfer error
Read task descriptor before DCMD (task execution) Master error Halt and report task ID in response mode error
CMD44 Command error Halt and report task ID in response mode error
CMD45 Command error Halt and report task ID in response mode error
CMD13 while controller in idle Command error Halt and task ID is not reported
CMD13 during CQ transaction Command error Halt and task ID is not reported
CMD46 / CMD47

Command error

Data error

DMA error

Halt and report ID in data transfer error
DCMD Command error Halt and report task ID in response mode error
DCMD Data timeout error Halt and report task ID in response mode error

Data transfer error in task error information is:

  • set to 1 when error appears during CMD46 or CMD47
  • clear to 0 when error appears during CMD44, CMD45, or DCMD

Response mode error in task error information is:

  • set to 1 when error appears during CMD44, CMD45, or DCMD
  • clear to 0 when error appears during CMD46 or CMD47

Task error information does not change when CQ is disabled or halted.