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author | Brian Norris <computersforpeace@gmail.com> | 2013-08-20 04:30:22 (GMT) |
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committer | Matthew Weigel <Matthew.Weigel@freescale.com> | 2014-12-11 18:37:09 (GMT) |
commit | a80b39bb6ee4a8a70fc47ec632aa76f9de8e108e (patch) | |
tree | b5ef13fd790e3146eefa5dc980b173ec313adb06 /Documentation/arm/cluster-pm-race-avoidance.txt | |
parent | 39b7c64c722ec47e2799742b14b77df009765080 (diff) | |
download | linux-fsl-qoriq-a80b39bb6ee4a8a70fc47ec632aa76f9de8e108e.tar.xz |
mtd: m25p80: remove M25PXX_USE_FAST_READ Kconfig
Remove the compile-time option for FAST_READ, since we have run-time
support for detecting it. This refactors the logic for enabling
fast-read, such that for DT-enabled devices, we honor the
"m25p,fast-read" property but for non-DT devices, we default to using
FAST_READ whenever the flash device supports it.
Normal READ and FAST_READ differ only in the following:
* FAST_READ supports SPI higher clock frequencies [1]
* number of dummy cycles; FAST_READ requires 8 dummy cycles (whereas
READ requires 0) to allow the flash sufficient setup time, even when
running at higher clock speeds
Thus, for flash chips which support FAST_READ, there is otherwise no
limiting reason why we cannot use the FAST_READ opcode instead of READ.
It simply allows the SPI controller to run at higher clock rates. So
theoretically, nobody should be needing the compile-time option anyway.
[1] I have a Spansion S25FL128S datasheet which says:
"The maximum operating clock frequency for the READ command is 50
MHz."
And:
"The maximum operating clock frequency for FAST READ command is 133
MHz."
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
(cherry picked from commit ddba7c5ad797f4b878f4e177ef300c1f9837cd29)
Change-Id: I205637becab372f43d3e8e741f20d35aac79a5fe
Reviewed-on: http://git.am.freescale.net:8181/20036
Tested-by: Review Code-CDREVIEW <CDREVIEW@freescale.com>
Reviewed-by: Zhengxiong Jin <Jason.Jin@freescale.com>
Diffstat (limited to 'Documentation/arm/cluster-pm-race-avoidance.txt')
0 files changed, 0 insertions, 0 deletions