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| author | Brian Norris <computersforpeace@gmail.com> | 2013-08-20 06:30:22 +0200 |
|---|---|---|
| committer | Brian Norris <computersforpeace@gmail.com> | 2013-11-07 08:33:06 +0100 |
| commit | ddba7c5ad797f4b878f4e177ef300c1f9837cd29 (patch) | |
| tree | e0f9934ced1dc0430c45697297e95616a19f22b8 /drivers/mtd | |
| parent | mtd: m25p80: re-align ID entries (diff) | |
| download | linux-ddba7c5ad797f4b878f4e177ef300c1f9837cd29.tar.xz linux-ddba7c5ad797f4b878f4e177ef300c1f9837cd29.zip | |
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>
Diffstat (limited to 'drivers/mtd')
| -rw-r--r-- | drivers/mtd/devices/Kconfig | 7 | ||||
| -rw-r--r-- | drivers/mtd/devices/m25p80.c | 11 |
2 files changed, 6 insertions, 12 deletions
diff --git a/drivers/mtd/devices/Kconfig b/drivers/mtd/devices/Kconfig index 74ab4b7e523e..01281382180b 100644 --- a/drivers/mtd/devices/Kconfig +++ b/drivers/mtd/devices/Kconfig @@ -95,13 +95,6 @@ config MTD_M25P80 if you want to specify device partitioning or to use a device which doesn't support the JEDEC ID instruction. -config M25PXX_USE_FAST_READ - bool "Use FAST_READ OPCode allowing SPI CLK >= 50MHz" - depends on MTD_M25P80 - default y - help - This option enables FAST_READ access supported by ST M25Pxx. - config MTD_SPEAR_SMI tristate "SPEAR MTD NOR Support through SMI controller" depends on PLAT_SPEAR diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c index 7e3ec7ae727f..d6c5c57380f8 100644 --- a/drivers/mtd/devices/m25p80.c +++ b/drivers/mtd/devices/m25p80.c @@ -1055,13 +1055,14 @@ static int m25p_probe(struct spi_device *spi) flash->page_size = info->page_size; flash->mtd.writebufsize = flash->page_size; - flash->fast_read = false; - if (np && of_property_read_bool(np, "m25p,fast-read")) + if (np) + /* If we were instantiated by DT, use it */ + flash->fast_read = of_property_read_bool(np, "m25p,fast-read"); + else + /* If we weren't instantiated by DT, default to fast-read */ flash->fast_read = true; -#ifdef CONFIG_M25PXX_USE_FAST_READ - flash->fast_read = true; -#endif + /* Some devices cannot do fast-read, no matter what DT tells us */ if (info->flags & M25P_NO_FR) flash->fast_read = false; |