path: root/drivers/net/dsa/sja1105/sja1105_dynamic_config.c

// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2018-2019, Vladimir Oltean <olteanv@gmail.com>
 */
#include "sja1105.h"

/* In the dynamic configuration interface, the switch exposes a register-like
 * view of some of the static configuration tables.
 * Many times the field organization of the dynamic tables is abbreviated (not
 * all fields are dynamically reconfigurable) and different from the static
 * ones, but the key reason for having it is that we can spare a switch reset
 * for settings that can be changed dynamically.
 *
 * This file creates a per-switch-family abstraction called
 * struct sja1105_dynamic_table_ops and two operations that work with it:
 * - sja1105_dynamic_config_write
 * - sja1105_dynamic_config_read
 *
 * Compared to the struct sja1105_table_ops from sja1105_static_config.c,
 * the dynamic accessors work with a compound buffer:
 *
 * packed_buf
 *
 * |
 * V
 * +-----------------------------------------+------------------+
 * |              ENTRY BUFFER               |  COMMAND BUFFER  |
 * +-----------------------------------------+------------------+
 *
 * <----------------------- packed_size ------------------------>
 *
 * The ENTRY BUFFER may or may not have the same layout, or size, as its static
 * configuration table entry counterpart. When it does, the same packing
 * function is reused (bar exceptional cases - see
 * sja1105pqrs_dyn_l2_lookup_entry_packing).
 *
 * The reason for the COMMAND BUFFER being at the end is to be able to send
 * a dynamic write command through a single SPI burst. By the time the switch
 * reacts to the command, the ENTRY BUFFER is already populated with the data
 * sent by the core.
 *
 * The COMMAND BUFFER is always SJA1105_SIZE_DYN_CMD bytes (one 32-bit word) in
 * size.
 *
 * Sometimes the ENTRY BUFFER does not really exist (when the number of fields
 * that can be reconfigured is small), then the switch repurposes some of the
 * unused 32 bits of the COMMAND BUFFER to hold ENTRY data.
 *
 * The key members of struct sja1105_dynamic_table_ops are:
 * - .entry_packing: A function that deals with packing an ENTRY structure
 *		     into an SPI buffer, or retrieving an ENTRY structure
 *		     from one.
 *		     The @packed_buf pointer it's given does always point to
 *		     the ENTRY portion of the buffer.
 * - .cmd_packing: A function that deals with packing/unpacking the COMMAND
 *		   structure to/from the SPI buffer.
 *		   It is given the same @packed_buf pointer as .entry_packing,
 *		   so most of the time, the @packed_buf points *behind* the
 *		   COMMAND offset inside the buffer.
 *		   To access the COMMAND portion of the buffer, the function
 *		   knows its correct offset.
 *		   Giving both functions the same pointer is handy because in
 *		   extreme cases (see sja1105pqrs_dyn_l2_lookup_entry_packing)
 *		   the .entry_packing is able to jump to the COMMAND portion,
 *		   or vice-versa (sja1105pqrs_l2_lookup_cmd_packing).
 * - .access: A bitmap of:
 *	OP_READ: Set if the hardware manual marks the ENTRY portion of the
 *		 dynamic configuration table buffer as R (readable) after
 *		 an SPI read command (the switch will populate the buffer).
 *	OP_WRITE: Set if the manual marks the ENTRY portion of the dynamic
 *		  table buffer as W (writable) after an SPI write command
 *		  (the switch will read the fields provided in the buffer).
 *	OP_DEL: Set if the manual says the VALIDENT bit is supported in the
 *		COMMAND portion of this dynamic config buffer (i.e. the
 *		specified entry can be invalidated through a SPI write
 *		command).
 *	OP_SEARCH: Set if the manual says that the index of an entry can
 *		   be retrieved in the COMMAND portion of the buffer based
 *		   on its ENTRY portion, as a result of a SPI write command.
 *		   Only the TCAM-based FDB table on SJA1105 P/Q/R/S supports
 *		   this.
 *	OP_VALID_ANYWAY: Reading some tables through the dynamic config
 *			 interface is possible even if the VALIDENT bit is not
 *			 set in the writeback. So don't error out in that case.
 * - .max_entry_count: The number of entries, counting from zero, that can be
 *		       reconfigured through the dynamic interface. If a static
 *		       table can be reconfigured at all dynamically, this
 *		       number always matches the maximum number of supported
 *		       static entries.
 * - .packed_size: The length in bytes of the compound ENTRY + COMMAND BUFFER.
 *		   Note that sometimes the compound buffer may contain holes in
 *		   it (see sja1105_vlan_lookup_cmd_packing). The @packed_buf is
 *		   contiguous however, so @packed_size includes any unused
 *		   bytes.
 * - .addr: The base SPI address at which the buffer must be written to the
 *	    switch's memory. When looking at the hardware manual, this must