diff options
author | Dinh Nguyen <Dinh.Nguyen@freescale.com> | 2010-08-17 16:46:40 -0500 |
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committer | Dinh Nguyen <Dinh.Nguyen@freescale.com> | 2010-09-01 10:42:59 -0500 |
commit | 3eb9039c5392abaabd96d08c0006ea4066346a60 (patch) | |
tree | 1b23d62933572db70a4aef7476a07e73f75e43d1 /Documentation | |
parent | 4dcb1e4f577f7331930301798da548447208f35a (diff) |
ENGR00126692-3: Upgrade kernel to 2.6.35
This patch contains changes to /drivers files
Contains all checkpatch and copyright fixes.
Acked-by: Rob Herring <r.herring@freescale.com>
Signed-off-by: Dinh Nguyen <Dinh.Nguyen@freescale.com>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/imx_nfc.txt | 369 |
1 files changed, 369 insertions, 0 deletions
diff --git a/Documentation/imx_nfc.txt b/Documentation/imx_nfc.txt new file mode 100644 index 000000000000..7fec999c2884 --- /dev/null +++ b/Documentation/imx_nfc.txt @@ -0,0 +1,369 @@ +i.MX NAND Flash Controller Driver Documentation +=============================================== + + +Definitions of Terms +==================== + +To avoid confusion, let's carefully define some of the terms we'll be using: + + "NAND Flash Chip" or "Chip" + A NAND Flash storage array and controller (including a chip select + signal, ready/busy signal, data register, etc.). + + "NAND Flash Package" or "Package" + A hardware package containing one or more NAND Flash chips that share + data lines and most control signals, but with separate chip select + and ready/busy signals. Package "boundaries" are unimportant to MTD. + + "NAND Flash Medium" or "Medium" + A collection of one or more NAND Flash chips that the system views as + logically contiguous. + + "Memory Technology Device" or "MTD" + An abstraction of underlying memory hardware, represented by a single + struct mtd_info. + + "NAND Flash MTD" + An abstraction of a NAND Flash medium that is represented by a single + struct nand_chip (the name of this structure is misleading because it + has evolved to represent an entire medium, not just a single chip). + All the physical chips in a NAND Flash MTD medium have answered the + "Read ID" command with the same manufacturer code and device code and + are presumed to have identical characteristics. + + "NAND Flash MTD Hardware-independent Layer" or "HIL" + The code that implements an MTD interface and drives all NAND Flash + MTDs. + + "NAND Flash MTD Hardware Abstraction Layer" or "HAL" + Code that implements the internal NAND Flash hardware model and + matches it to specific hardware. + + "NAND Flash MTD Reference Implementation" + A reference implementation of a HAL "stack." + + "Out-of-Band" or "OOB" + An adjective describing information that is not part of the "data" in + a NAND Flash page. NAND Flash pages are generally described in terms + of the amount of data they can hold (e.g., "2K pages" or "4K pages"). + The physical page size is actually larger than this and the + additional bytes are called "out-of-band." + + + +The Structure of the MTD NAND Flash System +========================================== + +The following figure illustrates how control flows down from the system's +MTD interface into the NAND Flash MTD system and down to the hardware- +specific implementation (this driver): + + + + / +---------------------------------------+ + | | MTD | + | +---------------------------------------+ + MTD | | + | | +----------+ + | | | | + | v v | + \ ======================================== | + - struct mtd_info | + / ======================================== | + | | | + | v | + | +---------------------------------------+ | + | | NAND Flash MTD | | + NAND Flash | | Interface Functions | | + Hardware- | +---------------------------------------+ | + Independent | | | | + Layer | | v | + (HIL) | +-------------+ | +-------------+ +-------------+ + | | Init | | | Support | | Reference | + | | Functions | | | Functions | |BBT Functions| + | +-------------+ | +-------------+ +-------------+ + | | | | ^ + | v v v | + \ ======================================== | + - struct nand_chip | + / ======================================== | + | | ^ | ^ | | + NAND Flash | | | | | | | + Hardware | v | v | | | + Abstraction | +--------------+ +---------------+ | | + Layer | | Hardware- | | Reference | +-----------+ + (HAL) | | Specific | | | + | |Implementation| |Implementations| + \ +--------------+ +---------------+ + + + +The function pointers and attributes in struct mtd_info embody an abstract +model of memory technology devices. + +The struct nand_chip is an aggregation of two categories of function pointers +and attributes: + + - Function pointers and attributes used by the HIL. These members embody + an abstract model of NAND Flash media, or a hardware abstraction + layer (HAL). + + - Function pointers and attributes used by the reference implementations. + +The single most confusing thing about the MTD NAND Flash system is that +struct nand_chip contains all the main HAL members mixed up with all the +members used only by the reference implementation, without any clear +distinction. Recognizing the distinction is critical for understanding the +relationship between the HIL and HAL, and can greatly simplify driver +implementation. + +The fundamental operations represented by the function pointers in +struct nand_chip fall into the following categories (from conceptually +"low-level" to "high-level"): + + - Signal Control + - Chip Control + - Low-level I/O + - ECC Control + - ECC-aware I/O + - Error Recovery + - High-level I/O + - Bad Block Management + +The HIL uses only the following "Replaceable" function pointers in +struct nand_chip: + + - Signal Control + - None + - Chip Control + - dev_ready + - select_chip + - cmdfunc + - waitfunc + - Low-level I/O + - read_byte + - ECC Control + - None + - ECC-aware I/O + - ecc.read_page + - ecc.read_page_raw + - Error Recovery + - None + - High-level I/O + - write_page + - ecc.read_oob + - ecc.write_oob + - Bad Block Management + - block_bad + - block_markbad + - scan_bbt + +Note that the HIL calls erase_cmd, but this member is marked "Internal." + +The HIL uses only the following commands with cmdfunc: + + * NAND_CMD_STATUS + - nand_check_wp() - Checks if the current chip is + write-protected. + * NAND_CMD_READID + - nand_get_flash_type() - Gets information about the first chip. + - nand_scan_ident() - Scans for additional chips. + * NAND_CMD_RESET + - nand_do_write_oob() - Clears a bug observed on the + Toshiba TC5832DC and DiskOnChip 2000. + * NAND_CMD_READ0 + - nand_do_read_ops() - Used to begin a full page read (both with + and without ECC). + * NAND_CMD_ERASE1 + - single_erase_cmd() - Starts a block erase operation. + - multi_erase_cmd() - Starts a block erase operation. + * NAND_CMD_ERASE2 + - single_erase_cmd() - Finishes a block erase operation. + - multi_erase_cmd() - Finishes a block erase operation. + + +Since this is all the HIL uses, this is all a driver needs to implement. + + + +The Structure of the imx_nfc Driver +=================================== + +This driver supports many different versions of underlying controller, and +also supports higher-level abstractions like interleaving. To facilitate this +versatility, the code is layered as shown in the following diagram: + + + +--------------------------------------+ + | MTD | + +--------------------------------------+ + | NAND Flash MTD | + ======================================== <-- struct nand_chip + / | MTD Interface Layer (mil_*) | + | | +----------------------------------+ + | | | Medium Abstraction Layer (mal_*) | + imx_nfc | | | | + driver | | | +------------------------+ + | | | | NFC Utils (nfc_util_*) | + | ======================================== <-- struct nfc_hal + \ | NFC HAL (nfc_x_y_*) | + ======================================== <-- Hardware Interface + | NFC Hardware | + +--------------------------------------+ + + +MTD Interface Layer +------------------- +This layer includes functions that the NAND Flash MTD system calls directly. +In a manner of speaking, this layer "parses" the function calls made by MTD +and translates them into fundamental operations understood by the Medium +Abstraction Layer. Some simple operations don't need any abstraction, so code +in this layer can sometimes use the NFC HAL directly. + + +Medium Abstraction Layer +------------------------ +This layer implements the abstract model of the NAND Flash medium and hides +details that shouldn't concern higher layers (e.g., interleaving). + + +NFC Utilities +------------- +These functions make it easier to use the NFC HAL. Even though this layer +is shown above the NFC HAL in the diagram, it's actually possible for the +NFC HAL to call some of these functions. + + +NFC HAL +------- +This layer implements the abstract model of an i.MX NAND Flash controller. + + +Other Collections of Functions +------------------------------ + +- System Interface + - imx_nfc_* + +- sysfs Interface + - get_module_* + - set_module_* + - show_device_* + - store_device_* + + + + +i.MX NAND Flash Controller Versions +=================================== + +The i.MX NAND Flash controller (NFC) has evolved over time. Both its memory +layout and behaviors have changed. In this driver, we use major and minor +version numbers to label these stages in the NFC's evolution. These version +numbers are very useful, but they are entirely a figment of this driver's +imagination -- you will never find them in Freescale hardware reference +manuals. + +When the platform code instantiates an i.MX NFC device, it provides a struct +imx_nfc_platform_data that contains platform-specific information. This +includes the major and minor version numbers for the NFC. This driver uses +the version numbers to select an appopriate NFC HAL structure. + + + +i.MX NFC Memory Map +=================== + +While many things have changed during the evolution of the NFC, much has +remained the same. All i.MX NFCs have two or three essential memory-mapped +regions: a set of buffers, and one or two sets of registers (one on the AXI +bus and perhaps a second on the IP bus). + +The buffer area contains the captive memory to which the NFC writes data +received from the NAND Flash medium. This area is subdivided into several +contiguous "main" buffers that hold 512-byte chunks of data, and several +"spare" buffers that hold varying-size chunks of out-of-band bytes. The +number of main buffers is always the same as the number of spare buffers, but +the exact count and the size of the spare buffers varies across NFC versions. + +The register areas contain the NFC's control interface. Some versions have +only one set of registers, and some have two. + +The platform-specific resources passed to this driver include the starting +and ending physical addresses of the buffer and register areas. This driver +maps those physical addresses to virtual addresses, and then uses version- +specific offsets and bit masks to operate the NFC. + + + +Matching the NAND Flash MTD Page Model with the i.MX NFC +======================================================== + +The NAND Flash MTD HAL model views a page as containing two essentially +independent groups of bytes: "data" bytes and "out-of-band" bytes. If the +underlying physical format has data and out-of-band bytes distributed across +the page, they must be reassembled before being delivered to the caller +(e.g., see the function nand_read_page_syndrome(), which is part of the +reference implementation). + +The i.MX NFC hardware imposes both a physical page layout and a layout in its +memory buffer that differ from the HAL model. The following figure shows how +all these layouts relate to each other: + + + i.MX NFC i.MX NFC + Physical Memory NAND Flash + Page Buffers MTD Model + + +--------+ +--------+ +--------+ + |OOB[N-1]| |OOB[N-1]| |OOB[N-1]| + +--------+ +--------+ +--------+ + | | <gap> |OOB[ 1 ]| + | Data | +--------+ +--------+ + | [N-1] | |OOB[ 1 ]| |OOB[ 0 ]| + | | +--------+ +--------+ + +--------+ <gap> + ... +--------+ +--------+ + +--------+ |OOB[ 0 ]| | | + |OOB[ 1 ]| +--------+ | Data | + +--------+ | | | [N-1] | + | | | Data | | | + | Data | | [N-1] | +--------+ + | [ 1 ] | | | | | + | | +--------+ | Data | + +--------+ ... | [ 1 ] | + |OOB[ 0 ]| +--------+ | | + +--------+ | | +--------+ + | | | Data | | | + | Data | | [ 1 ] | | Data | + | [ 0 ] | | | | [ 0 ] | + | | +--------+ | | + +--------+ | | +--------+ + | Data | + | [ 0 ] | + | | + +--------+ + + +The NFC memory is *almost* what we want, but not quite. The problems are: + + 1) There are gaps between the out-of-band fragments. + + 2) The NFC memory responds only to 16-byte or 32-byte reads and writes. + +To resolve these problems, we've encapsulated the NFC memory behind these +functions: + + nfc_util_copy_from_the_nfc() - Copies data to main memory from the the NFC. + nfc_util_copy_to_the_nfc() - Copies data from main memory to the NFC. + +These functions don't take pointers to locations within the NFC memory - they +take a "column address." These functions know how to skip over the gaps and +handle the NFC memory such that it looks like all the data and out-of-band +bytes are completely contiguous. They also handle copying arbitrary bytes +from/to a memory that only responds to 16- or 32-byte reads/writes. If you're +accessing the NFC memory without these functions, you're *probably* doing +something wrong. + + |