Xilinx SD-FEC Driver¶

Overview¶

This driver supports SD-FEC Integrated Block for Zynq Ultrascale+™ RFSoCs.

For a full description of SD-FEC core features, see the SD-FEC Product Guide (PG256)

This driver supports the following features:

Retrieval of the Integrated Block configuration and status information

Configuration of LDPC codes

Configuration of Turbo decoding

Monitoring errors

Missing features, known issues, and limitations of the SD-FEC driver are as follows:

Only allows a single open file handler to any instance of the driver at any time

Reset of the SD-FEC Integrated Block is not controlled by this driver

Does not support shared LDPC code table wraparound

The device tree entry is described in: linux-xlnx/Documentation/devicetree/bindings/misc/xlnx,sd-fec.txt

Modes of Operation¶

The driver works with the SD-FEC core in two modes of operation:

Run-time configuration

Programmable Logic (PL) initialization

Run-time Configuration¶

For Run-time configuration the role of driver is to allow the software application to do the following:

Load the configuration parameters for either Turbo decode or LDPC encode or decode

Activate the SD-FEC core

Monitor the SD-FEC core for errors

Retrieve the status and configuration of the SD-FEC core

Programmable Logic (PL) Initialization¶

For PL initialization, supporting logic loads configuration parameters for either the Turbo decode or LDPC encode or decode. The role of the driver is to allow the software application to do the following:

Activate the SD-FEC core

Monitor the SD-FEC core for errors

Retrieve the status and configuration of the SD-FEC core

Driver Structure¶

The driver provides a platform device where the probe and remove operations are provided.

probe: Updates configuration register with device-tree entries plus determines the current activate state of the core, for example, is the core bypassed or has the core been started.

The driver defines the following driver file operations to provide user application interfaces:

open: Implements restriction that only a single file descriptor can be open per SD-FEC instance at any time

release: Allows another file descriptor to be open, that is after current file descriptor is closed

poll: Provides a method to monitor for SD-FEC Error events

unlocked_ioctl: Provides the following ioctl commands that allows the application configure the SD-FEC core:

XSDFEC_START_DEV

XSDFEC_STOP_DEV

XSDFEC_GET_STATUS

XSDFEC_SET_IRQ

XSDFEC_SET_TURBO

XSDFEC_ADD_LDPC_CODE_PARAMS

XSDFEC_GET_CONFIG

XSDFEC_SET_ORDER

XSDFEC_SET_BYPASS

XSDFEC_IS_ACTIVE

XSDFEC_CLEAR_STATS

XSDFEC_SET_DEFAULT_CONFIG

Driver Usage¶

Overview¶

After opening the driver, the user should find out what operations need to be performed to configure and activate the SD-FEC core and determine the configuration of the driver. The following outlines the flow the user should perform:

Determine Configuration

Set the order, if not already configured as desired

Set Turbo decode, LPDC encode or decode parameters, depending on how the SD-FEC core is configured plus if the SD-FEC has not been configured for PL initialization

Enable interrupts, if not already enabled

Bypass the SD-FEC core, if required

Start the SD-FEC core if not already started

Get the SD-FEC core status

Monitor for interrupts

Stop the SD-FEC core

Note: When monitoring for interrupts if a critical error is detected where a reset is required, the driver will be required to load the default configuration.

Determine Configuration¶

Determine the configuration of the SD-FEC core by using the ioctl XSDFEC_GET_CONFIG.

Set the Order¶

Setting the order determines how the order of Blocks can change from input to output.

Setting the order is done by using the ioctl XSDFEC_SET_ORDER

Setting the order can only be done if the following restrictions are met:

The state member of struct xsdfec_status filled by the ioctl XSDFEC_GET_STATUS indicates the SD-FEC core has not STARTED

Add LDPC Codes¶

The following steps indicate how to add LDPC codes to the SD-FEC core:

Use the auto-generated parameters to fill the struct xsdfec_ldpc_params for the desired LDPC code.

Set the SC, QA, and LA table offsets for the LPDC parameters and the parameters in the structure struct xsdfec_ldpc_params

Set the desired Code Id value in the structure struct xsdfec_ldpc_params

Add the LPDC Code Parameters using the ioctl XSDFEC_ADD_LDPC_CODE_PARAMS

For the applied LPDC Code Parameter use the function xsdfec_calculate_shared_ldpc_table_entry_size() to calculate the size of shared LPDC code tables. This allows the user to determine the shared table usage so when selecting the table offsets for the next LDPC code parameters unused table areas can be selected.

Repeat for each LDPC code parameter.

Adding LDPC codes can only be done if the following restrictions are met:

The code member of struct xsdfec_config filled by the ioctl XSDFEC_GET_CONFIG indicates the SD-FEC core is configured as LDPC

The code_wr_protect of struct xsdfec_config filled by the ioctl XSDFEC_GET_CONFIG indicates that write protection is not enabled

The state member of struct xsdfec_status filled by the ioctl XSDFEC_GET_STATUS indicates the SD-FEC core has not started

Set Turbo Decode¶

Configuring the Turbo decode parameters is done by using the ioctl XSDFEC_SET_TURBO using auto-generated parameters to fill the struct xsdfec_turbo for the desired Turbo code.

Adding Turbo decode can only be done if the following restrictions are met:

The code member of struct xsdfec_config filled by the ioctl XSDFEC_GET_CONFIG indicates the SD-FEC core is configured as TURBO

The state member of struct xsdfec_status filled by the ioctl XSDFEC_GET_STATUS indicates the SD-FEC core has not STARTED

Enable Interrupts¶

Enabling or disabling interrupts is done by using the ioctl XSDFEC_SET_IRQ. The members of the parameter passed, struct xsdfec_irq, to the ioctl are used to set and clear different categories of interrupts. The category of interrupt is controlled as following:

enable_isr controls the tlast interrupts

enable_ecc_isr controls the ECC interrupts

If the code member of struct xsdfec_config filled by the ioctl XSDFEC_GET_CONFIG indicates the SD-FEC core is configured as TURBO then the enabling ECC errors is not required.

Bypass the SD-FEC¶

Bypassing the SD-FEC is done by using the ioctl XSDFEC_SET_BYPASS

Bypassing the SD-FEC can only be done if the following restrictions are met:

The state member of struct xsdfec_status filled by the ioctl XSDFEC_GET_STATUS indicates the SD-FEC core has not STARTED

Start the SD-FEC core¶

Start the SD-FEC core by using the ioctl XSDFEC_START_DEV

Get SD-FEC Status¶

Get the SD-FEC status of the device by using the ioctl XSDFEC_GET_STATUS, which will fill the struct xsdfec_status

Monitor for Interrupts¶

Use the poll system call to monitor for an interrupt. The poll system call waits for an interrupt to wake it up or times out if no interrupt occurs.

On return Poll revents will indicate whether stats and/or state have been updated

POLLPRI indicates a critical error and the user should use XSDFEC_GET_STATUS and XSDFEC_GET_STATS to confirm

POLLRDNORM indicates a non-critical error has occurred and the user should use XSDFEC_GET_STATS to confirm

Get stats by using the ioctl XSDFEC_GET_STATS

For critical error the isr_err_count or uecc_count member of struct xsdfec_stats is non-zero

For non-critical errors the cecc_count member of struct xsdfec_stats is non-zero

Get state by using the ioctl XSDFEC_GET_STATUS

For a critical error the state of xsdfec_status will indicate a Reset Is Required

Clear stats by using the ioctl XSDFEC_CLEAR_STATS

If a critical error is detected where a reset is required. The application is required to call the ioctl XSDFEC_SET_DEFAULT_CONFIG, after the reset and it is not required to call the ioctl XSDFEC_STOP_DEV

Note: Using poll system call prevents busy looping using XSDFEC_GET_STATS and XSDFEC_GET_STATUS

Stop the SD-FEC Core¶

Stop the device by using the ioctl XSDFEC_STOP_DEV

Set the Default Configuration¶

Load default configuration by using the ioctl XSDFEC_SET_DEFAULT_CONFIG to restore the driver.

Limitations¶

Users should not duplicate SD-FEC device file handlers, for example fork() or dup() a process that has a created an SD-FEC file handler.

Driver IOCTLs¶

XSDFEC_START_DEV¶

Description

ioctl to start SD-FEC core

This fails if the XSDFEC_SET_ORDER ioctl has not been previously called

XSDFEC_STOP_DEV¶

Description

ioctl to stop the SD-FEC core

XSDFEC_GET_STATUS¶

Description

ioctl that returns status of SD-FEC core

XSDFEC_SET_IRQ¶

Parameters

struct xsdfec_irq *: Pointer to the struct xsdfec_irq that contains the interrupt settings for the SD-FEC core

Description

ioctl to enable or disable irq

XSDFEC_SET_TURBO¶

Parameters

struct xsdfec_turbo *: Pointer to the struct xsdfec_turbo that contains the Turbo decode settings for the SD-FEC core

Description

ioctl that sets the SD-FEC Turbo parameter values

This can only be used when the driver is in the XSDFEC_STOPPED state

XSDFEC_ADD_LDPC_CODE_PARAMS¶

Parameters

struct xsdfec_ldpc_params *: Pointer to the struct xsdfec_ldpc_params that contains the LDPC code parameters to be added to the SD-FEC Block

Description ioctl to add an LDPC code to the SD-FEC LDPC codes

This can only be used when:

Driver is in the XSDFEC_STOPPED state
SD-FEC core is configured as LPDC
SD-FEC Code Write Protection is disabled

XSDFEC_GET_CONFIG¶

Parameters

struct xsdfec_config *: Pointer to the struct xsdfec_config that contains the current configuration settings of the SD-FEC Block

Description

ioctl that returns SD-FEC core configuration

XSDFEC_SET_ORDER¶

Parameters

struct unsigned long *: Pointer to the unsigned long that contains a value from the enum xsdfec_order

Description

ioctl that sets order, if order of blocks can change from input to output

This can only be used when the driver is in the XSDFEC_STOPPED state

XSDFEC_SET_BYPASS¶

Parameters

struct bool *: Pointer to bool that sets the bypass value, where false results in normal operation and false results in the SD-FEC performing the configured operations (same number of cycles) but output data matches the input data

Description

ioctl that sets bypass.

This can only be used when the driver is in the XSDFEC_STOPPED state

XSDFEC_IS_ACTIVE¶

Parameters

struct bool *: Pointer to bool that returns true if the SD-FEC is processing data

Description

ioctl that determines if SD-FEC is processing data

XSDFEC_CLEAR_STATS¶

Description

ioctl that clears error stats collected during interrupts

XSDFEC_GET_STATS¶

Parameters

struct xsdfec_stats *: Pointer to the struct xsdfec_stats that will contain the updated stats values

Description

ioctl that returns SD-FEC core stats

This can only be used when the driver is in the XSDFEC_STOPPED state

XSDFEC_SET_DEFAULT_CONFIG¶

Description

ioctl that returns SD-FEC core to default config, use after a reset

This can only be used when the driver is in the XSDFEC_STOPPED state

Driver Type Definitions¶

enum xsdfec_code¶: Code Type.

Constants

XSDFEC_TURBO_CODE: Driver is configured for Turbo mode.
XSDFEC_LDPC_CODE: Driver is configured for LDPC mode.

Description

This enum is used to indicate the mode of the driver. The mode is determined by checking which codes are set in the driver. Note that the mode cannot be changed by the driver.

enum xsdfec_order¶: Order

Constants

XSDFEC_MAINTAIN_ORDER: Maintain order execution of blocks.
XSDFEC_OUT_OF_ORDER: Out-of-order execution of blocks.

Description

This enum is used to indicate whether the order of blocks can change from input to output.

enum xsdfec_turbo_alg¶: Turbo Algorithm Type.

Constants

XSDFEC_MAX_SCALE: Max Log-Map algorithm with extrinsic scaling. When scaling is set to this is equivalent to the Max Log-Map algorithm.
XSDFEC_MAX_STAR: Log-Map algorithm.
XSDFEC_TURBO_ALG_MAX: Used to indicate out of bound Turbo algorithms.

Description

This enum specifies which Turbo Decode algorithm is in use.

enum xsdfec_state¶: State.

Constants

XSDFEC_INIT: Driver is initialized.
XSDFEC_STARTED: Driver is started.
XSDFEC_STOPPED: Driver is stopped.
XSDFEC_NEEDS_RESET: Driver needs to be reset.
XSDFEC_PL_RECONFIGURE: Programmable Logic needs to be recofigured.

Description

This enum is used to indicate the state of the driver.

enum xsdfec_axis_width¶: AXIS_WIDTH.DIN Setting for 128-bit width.

Constants

XSDFEC_1x128b: DIN data input stream consists of a 128-bit lane
XSDFEC_2x128b: DIN data input stream consists of two 128-bit lanes
XSDFEC_4x128b: DIN data input stream consists of four 128-bit lanes

Description

This enum is used to indicate the AXIS_WIDTH.DIN setting for 128-bit width. The number of lanes of the DIN data input stream depends upon the AXIS_WIDTH.DIN parameter.

enum xsdfec_axis_word_include¶: Words Configuration.

Constants

XSDFEC_FIXED_VALUE: Fixed, the DIN_WORDS AXI4-Stream interface is removed from the IP instance and is driven with the specified number of words.
XSDFEC_IN_BLOCK: In Block, configures the IP instance to expect a single DIN_WORDS value per input code block. The DIN_WORDS interface is present.
XSDFEC_PER_AXI_TRANSACTION: Per Transaction, configures the IP instance to expect one DIN_WORDS value per input transaction on the DIN interface. The DIN_WORDS interface is present.
XSDFEC_AXIS_WORDS_INCLUDE_MAX: Used to indicate out of bound Words Configurations.

Description

This enum is used to specify the DIN_WORDS configuration.

struct xsdfec_turbo¶: User data for Turbo codes.

Definition

struct xsdfec_turbo {
  __u32 alg;
  __u8 scale;
};

Members

alg: Specifies which Turbo decode algorithm to use
scale: Specifies the extrinsic scaling to apply when the Max Scale algorithm has been selected

Description

Turbo code structure to communicate parameters to XSDFEC driver.

struct xsdfec_ldpc_params¶: User data for LDPC codes.

Definition

struct xsdfec_ldpc_params {
  __u32 n;
  __u32 k;
  __u32 psize;
  __u32 nlayers;
  __u32 nqc;
  __u32 nmqc;
  __u32 nm;
  __u32 norm_type;
  __u32 no_packing;
  __u32 special_qc;
  __u32 no_final_parity;
  __u32 max_schedule;
  __u32 sc_off;
  __u32 la_off;
  __u32 qc_off;
  __u32 *sc_table;
  __u32 *la_table;
  __u32 *qc_table;
  __u16 code_id;
};

Members

n: Number of code word bits
k: Number of information bits
psize: Size of sub-matrix
nlayers: Number of layers in code
nqc: Quasi Cyclic Number
nmqc: Number of M-sized QC operations in parity check matrix
nm: Number of M-size vectors in N
norm_type: Normalization required or not
no_packing: Determines if multiple QC ops should be performed
special_qc: Sub-Matrix property for Circulant weight > 0
no_final_parity: Decide if final parity check needs to be performed
max_schedule: Experimental code word scheduling limit
sc_off: SC offset
la_off: LA offset
qc_off: QC offset
sc_table: Pointer to SC Table which must be page aligned
la_table: Pointer to LA Table which must be page aligned
qc_table: Pointer to QC Table which must be page aligned
code_id: LDPC Code

Description

This structure describes the LDPC code that is passed to the driver by the application.

struct xsdfec_status¶: Status of SD-FEC core.

Definition

struct xsdfec_status {
  __u32 state;
  __s8 activity;
};

Members

state: State of the SD-FEC core
activity: Describes if the SD-FEC instance is Active

struct xsdfec_irq¶: Enabling or Disabling Interrupts.

Definition

struct xsdfec_irq {
  __s8 enable_isr;
  __s8 enable_ecc_isr;
};

Members

enable_isr: If true enables the ISR
enable_ecc_isr: If true enables the ECC ISR

struct xsdfec_config¶: Configuration of SD-FEC core.

Definition

struct xsdfec_config {
  __u32 code;
  __u32 order;
  __u32 din_width;
  __u32 din_word_include;
  __u32 dout_width;
  __u32 dout_word_include;
  struct xsdfec_irq irq;
  __s8 bypass;
  __s8 code_wr_protect;
};

Members

code: The codes being used by the SD-FEC instance
order: Order of Operation
din_width: Width of the DIN AXI4-Stream
din_word_include: How DIN_WORDS are inputted
dout_width: Width of the DOUT AXI4-Stream
dout_word_include: HOW DOUT_WORDS are outputted
irq: Enabling or disabling interrupts
bypass: Is the core being bypassed
code_wr_protect: Is write protection of LDPC codes enabled

struct xsdfec_stats¶: Stats retrived by ioctl XSDFEC_GET_STATS. Used to buffer atomic_t variables from struct xsdfec_dev. Counts are accumulated until the user clears them.

Definition

struct xsdfec_stats {
  __u32 isr_err_count;
  __u32 cecc_count;
  __u32 uecc_count;
};

Members

isr_err_count: Count of ISR errors
cecc_count: Count of Correctable ECC errors (SBE)
uecc_count: Count of Uncorrectable ECC errors (MBE)

struct xsdfec_ldpc_param_table_sizes¶: Used to store sizes of SD-FEC table entries for an individual LPDC code parameter.

Definition

struct xsdfec_ldpc_param_table_sizes {
  __u32 sc_size;
  __u32 la_size;
  __u32 qc_size;
};

Members

sc_size: Size of SC table used
la_size: Size of LA table used
qc_size: Size of QC table used