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This is a driver for mtk spi-nor controller using spi-mem interface. The same controller already has limited support provided by mtk-quadspi driver under spi-nor framework and this new driver is a replacement for the old one. Comparing to the old driver, this driver has following advantages: 1. It can handle any full-duplex spi transfer up to 6 bytes, and this is implemented using generic spi interface. 2. It take account into command opcode properly. The reading routine in this controller can only use 0x03 or 0x0b as opcode on 1-1-1 transfers, but old driver doesn't implement this properly. This driver checks supported opcode explicitly and use (1) to perform unmatched operations. 3. It properly handles SFDP reading. Old driver can't read SFDP due to the bug mentioned in (2). 4. It can do 1-2-2 and 1-4-4 fast reading on spi-nor. These two ops requires parsing SFDP, which isn't possible in old driver. And the old driver is only flagged to support 1-1-2 mode. 5. It takes advantage of the DMA feature in this controller for long reads and supports IRQ on DMA requests to free cpu cycles from polling status registers on long DMA reading. It achieves up to 17.5MB/s reading speed (1-4-4 mode) which is way faster than the old one. IRQ is implemented as optional to maintain backward compatibility. Signed-off-by: Chuanhong Guo <gch981213@gmail.com> Link: https://lore.kernel.org/r/20200306085052.28258-3-gch981213@gmail.com Signed-off-by: Mark Brown <broonie@kernel.org>
Linux kernel
============
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