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authorBrian Norris <computersforpeace@gmail.com>2014-05-06 00:46:17 +0530
committerTom Rini <trini@ti.com>2014-06-06 17:46:03 -0400
commit27ce9e4290b168a1241699d411678959aaf9649b (patch)
tree7f341734dddc4a061058efa5a297461d99b53afa /arch
parentb9ae609fdbb7f8149a13bb9c67006b7237cbf83e (diff)
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mtd: nand: force NAND_CMD_READID onto 8-bit bus
As per following Sections in ONFI Spec, NAND_CMD_READID should use only lower 8-bit for transfering command, address and data even on x16 NAND device. *Section: Target Initialization" "The Read ID and Read Parameter Page commands only use the lower 8-bits of the data bus. The host shall not issue commands that use a word data width on x16 devices until the host determines the device supports a 16-bit data bus width in the parameter page." *Section: Bus Width Requirements* "When the host supports a 16-bit bus width, only data is transferred at the 16-bit width. All address and command line transfers shall use only the lower 8-bits of the data bus. During command transfers, the host may place any value on the upper 8-bits of the data bus. During address transfers, the host shall set the upper 8-bits of the data bus to 00h." Thus porting following commit from linux-kernel to ensure that column address is not altered to align to x16 bus when issuing NAND_CMD_READID command. commit 3dad2344e92c6e1aeae42df1c4824f307c51bcc7 mtd: nand: force NAND_CMD_READID onto 8-bit bus Author: Brian Norris <computersforpeace@gmail.com> (preserving authorship) The NAND command helpers tend to automatically shift the column address for x16 bus devices, since most commands expect a word address, not a byte address. The Read ID command, however, expects an 8-bit address (i.e., 0x00, 0x20, or 0x40 should not be translated to 0x00, 0x10, or 0x20). This fixes the column address for a few drivers which imitate the nand_base defaults. Signed-off-by: Pekon Gupta <pekon@ti.com>
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