Hi,
On 04/04/2017 11:16 PM, Richard Leitner wrote:
> Some eMMCs disable their hardware reset line (RST_N) by default. To enable
> it the host must set the corresponding bit in ECSD. An example for such
> a device is the Micron MTFCxGACAANA-4M.
>
> This patch adds a new mmc-card devicetree property to let the host enable
> this feature during card initialization.
>
> Signed-off-by: Richard Leitner <richard.leitner@xxxxxxxxxxx>
> ---
> Documentation/devicetree/bindings/mmc/mmc-card.txt | 3 +++
> drivers/mmc/core/mmc.c | 21 +++++++++++++++++++++
> 2 files changed, 24 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mmc/mmc-card.txt b/Documentation/devicetree/bindings/mmc/mmc-card.txt
> index a70fcd6..8590a40 100644
> --- a/Documentation/devicetree/bindings/mmc/mmc-card.txt
> +++ b/Documentation/devicetree/bindings/mmc/mmc-card.txt
> @@ -12,6 +12,9 @@ Required properties:
> Optional properties:
> -broken-hpi : Use this to indicate that the mmc-card has a broken hpi
> implementation, and that hpi should not be used
> +-enable-hw-reset : some eMMC devices have disabled the hw reset functionality
> + (RST_N_FUNCTION) by default. By adding this property the
> + host will enable it during initialization.
As i know, RST_N_FUNCTION is controlled bit[1:0]
0x0 : RST_n disabled (by default)
0x1 : permanently enabled
0x2 : permanently disabled
I think that it needs to add the description about these..
>
> Example:
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index b502601..518d0e3 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1520,9 +1520,16 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
> int err;
> u32 cid[4];
> u32 rocr;
> + struct device_node *np;
> + bool enable_rst_n = false;
>
> WARN_ON(!host->claimed);
>
> + np = mmc_of_find_child_device(host, 0);
> + if (np && of_device_is_compatible(np, "mmc-card"))
> + enable_rst_n = of_property_read_bool(np, "enable-hw-reset");
> + of_node_put(np);
> +
> /* Set correct bus mode for MMC before attempting init */
> if (!mmc_host_is_spi(host))
> mmc_set_bus_mode(host, MMC_BUSMODE_OPENDRAIN);
> @@ -1810,6 +1817,20 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
> }
> }
>
> + /*
> + * try to enable RST_N if requested
> + * This is needed because some eMMC chips disable this function by
> + * default.
> + */
> + if (enable_rst_n) {
> + err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> + EXT_CSD_RST_N_FUNCTION, EXT_CSD_RST_N_ENABLED,
> + card->ext_csd.generic_cmd6_time);
> + if (err && err != -EBADMSG)
> + pr_warn("%s: Enabling RST_N feature failed\n",
> + mmc_hostname(card->host));
> + }
If enabled hw-reset, it doesn't need to re-enable this bit.
i didn't check the mmc-util..
If mmc-util provides the changing this, the using mmc-util is better than this.
Best Regards,
Jaehoon Chung
> +
> if (!oldcard)
> host->card = card;
>
>
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