On 15 November 2017 at 10:01, <yinbo.zhu@xxxxxxx> wrote:
> From: "yinbo.zhu" <yinbo.zhu@xxxxxxx>
>
> 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@xxxxxxx>
> ---
> drivers/mmc/host/sdhci-of-esdhc.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c
> index 023c24bd0d94..2744dd58a573 100644
> --- a/drivers/mmc/host/sdhci-of-esdhc.c
> +++ b/drivers/mmc/host/sdhci-of-esdhc.c
> @@ -498,6 +498,12 @@ 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")) {
It's better to use the ->data pointer in the struct of_device_id for
this kind of variant data.
In ->probe() you then call of_match_device() and pick up the ->data
pointer and assign it to your driver private data.
Many drivers already do like this. Have a look at dw_mmc-exynos.c for example.
> + 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);
Kind regards
Uffe
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