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| author | yinbo.zhu <yinbo.zhu@nxp.com> | 2017-10-25 09:41:09 (GMT) |
|---|---|---|
| committer | Xie Xiaobo <xiaobo.xie@nxp.com> | 2017-12-12 07:32:40 (GMT) |
| commit | 946747446edd2ec83abb653aaf64c7a031fd9097 (patch) | |
| tree | ad0f7231b18763a3fcac573b9616217efff1d340 | |
| parent | e51ae985273348fbaffffa58c0e3eca9a0ab773e (diff) | |
| download | linux-946747446edd2ec83abb653aaf64c7a031fd9097.tar.xz | |
mmc: sdhci-of-esdhc: Workaround for reducing the maximum speed on ls1021atwr
In SDHC high speed AC timing, the tshivkh parameter
is defined as input setup times:SDHC_CMD, SDHC_DATx,
to SDHC_CLK. The value of the tshivkh should be 2.5 ns
considering the round trip delay, board/data skew.
However, because of this erratum, it needs
at least 4.1 ns.
eSDHC cannot run at the maximum clock speed for the
high speed mode, or there is a limit on the length
of the trace on the board for data, command, and
clock lines of the SDHC.
Signed-off-by: yinbo.zhu <yinbo.zhu@nxp.com>
| -rw-r--r-- | drivers/mmc/host/sdhci-of-esdhc.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c index bfa0582..4aaa790 100644 --- a/drivers/mmc/host/sdhci-of-esdhc.c +++ b/drivers/mmc/host/sdhci-of-esdhc.c @@ -502,6 +502,12 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock) clock -= 5000000; } + /* Workaround to reduce the clock frequency for ls1021a esdhc */ + if (of_find_compatible_node(NULL, NULL, "fsl,ls1021a-esdhc")) { + if (clock == 50000000) + clock = 46500000; + } + temp = sdhci_readl(host, ESDHC_SYSTEM_CONTROL); temp &= ~(ESDHC_CLOCK_SDCLKEN | ESDHC_CLOCK_IPGEN | ESDHC_CLOCK_HCKEN | ESDHC_CLOCK_PEREN | ESDHC_CLOCK_MASK); |