[PATCH v3 0/8] Add the Quadspi driver for vf610-twr

[Gupta, Pekon]

> 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