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 <[email protected]> --- 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. 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 (!oldcard) host->card = card; -- 2.1.4
