> 于 2013年09月05日 12:25, Gupta, Pekon 写道:
> > I would rather suggest to get these values from DT bindings specific to
> could you show me what values should i set in the DT bindings?
> The spi nor command? or the dummy? or something else?
>
Taking example of READ command for S25FL128S NOR flash devices..
S25FL128S supports following flavors of READ modes.
4FAST_READ Read Fast (4-byte Address) 0C
4READ Read (4-byte Address) 13
4DOR Read Dual Out (4-byte Address) 3C
4QOR Read Quad Out (4-byte Address) 6C
4DIOR Dual I/O Read (4-byte Address) BC
4QIOR Quad I/O Read (4-byte Address) EC
4DDRFR Read DDR Fast (4-byte Address) 0E
4DDRDIOR DDR Dual I/O Read (4-byte Address) BE
4DDRQIOR DDR Quad I/O Read (4-byte Address) EE
But due to board constrains and your use-case, you would prefer only few
read modes. Those opcodes you can specify via following DT property.
"qspi, flash-read-command"
Same way you can have DT property for
"qspi, flash-write-command"
"qspi, flash-erase-command"
"qspi, flash-address-mode" = <4-byte/3-byte>
"qspi, flash-dummy-cycles" = <integer>
Example: How to select opcodes in DT ?
(step-1) eliminate opcode which cannot be used due to board constrains.
your board connects only 2 data I/O between device and controller, So you
cannot use any of the QUAD Read opcodes. Thus your choice is limited to
DUAL or SINGLE modes only.
(step-2) select opcode based on use-case.
(a) To maximize your throughput you would mostly use DUAL read opcode
- fsl-qspi, flash-read-opcode = 0x3C /* 4DOR Read Dual Out (4-byte Address) */
- fsl-qspi, flash-read-opcode = 0xBC /* 4DIOR Dual I/O Read (4-byte Address) */
(b) But If you are using XIP then you would single out to:
- fsl-qspi, flash-read-opcode = 0xBC /* 4DIOR Dual I/O Read (4-byte Address) */
Though I agree, end-user should be transparent of all these,
but this is better than asking them to submit patches for each new NOR device
..Any thoughts ?
with regards, pekon
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