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Traditionally, the command set used by SPI flash only supported a 3-byte address. However, large SPI flash (>= 32MiB, or 256Mib) require 4 bytes to address the entire flash. Most manufacturers have supplied a mode switch (via a "bank register writer", or a "enable 4-byte mode" command), which tells the flash to expect 4 address cycles from now on, instead of 3. This mode remains until power is cut, the reset line is triggered (on packages where present), or a command is sent to reset the flash or to reset the 3-byte addressing mode. As an alternative, some flash manufacturers have developed a new command set that accept a full 4-byte address. They can be used orthogonally to any of the modes; that is, they can be used when the flash is in either 3-byte or 4-byte address mode. Now, there are a number of reasons why the "stateful" 4-byte address mode switch may not be acceptable. For instance, some SoC's perform a dumb boot sequence in which they only send 3-byte read commands to the flash. However, if an unexpected reset occurs, the flash chip cannot be guaranteed to return to its 3-byte mode. Thus, the SoC controller and flash will not understand each other. (One might consider hooking up the aforementioned reset pin to the system reset line so that any system reset will reset the flash to 3-byte mode, but some packages do not provide this pin. And in some other packages, one must choose between having a reset pin and having enough pins for 4-output QSPI support. It is an error prone process choosing a flash that will support a hardware reset pin!) This patch provides support for the new stateless command set, so that we can avoid the problems that come with a stateful addressing mode change. The flash can be left in "3-byte mode" while still accessing the entire flash. Note that Spansion supports this command set on all its large flash (e.g, S25FL512S), and Macronix has begun supporting this command set on some new flash (e.g., MX25L25635F). For the moment, I don't know how to differentiate the Macronix that don't support this command set (e.g., MX25L25635E) from those that do, so this patch only supports Spansion. Signed-off-by: Brian Norris <computersforpeace@gmail.com> Acked-by: Marek Vasut <marex@denx.de> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> |
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| .. | ||
| chips | ||
| devices | ||
| lpddr | ||
| maps | ||
| nand | ||
| onenand | ||
| tests | ||
| ubi | ||
| afs.c | ||
| ar7part.c | ||
| bcm47xxpart.c | ||
| bcm63xxpart.c | ||
| cmdlinepart.c | ||
| ftl.c | ||
| inftlcore.c | ||
| inftlmount.c | ||
| Kconfig | ||
| Makefile | ||
| mtd_blkdevs.c | ||
| mtdblock.c | ||
| mtdblock_ro.c | ||
| mtdchar.c | ||
| mtdconcat.c | ||
| mtdcore.c | ||
| mtdcore.h | ||
| mtdoops.c | ||
| mtdpart.c | ||
| mtdsuper.c | ||
| mtdswap.c | ||
| nftlcore.c | ||
| nftlmount.c | ||
| ofpart.c | ||
| redboot.c | ||
| rfd_ftl.c | ||
| sm_ftl.c | ||
| sm_ftl.h | ||
| ssfdc.c | ||