mmc: core: Export a function mmc_sw_reset() to allow soft reset of cards

It's rather common that a firmware is loaded into an SDIO func device
memory, by the corresponding SDIO func driver during ->probe() time.

However, to actually start running the new firmware, sometimes a soft reset
(no power cycle) and a re-initialization of the card is needed. This is for
example the case with the Espressif ESP8089 WiFi chips, when connected to
an SDIO interface.

To cope with this scenario, let's add a new exported function,
mmc_sw_reset(), which may be called when a soft reset and re-initialization
of the card are needed.

The mmc_sw_reset() is implemented on top of a new bus ops callback, similar
to how the mmc_hw_reset() has been implemented.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Quentin Schulz <quentin.schulz@bootlin.com>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>

2 files changed, 25 insertions, 0 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 3e17c62..7a79dc1 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2451,6 +2451,30 @@ int mmc_hw_reset(struct mmc_host *host)
 }
 EXPORT_SYMBOL(mmc_hw_reset);
 
+int mmc_sw_reset(struct mmc_host *host)
+{
+	int ret;
+
+	if (!host->card)
+		return -EINVAL;
+
+	mmc_bus_get(host);
+	if (!host->bus_ops || host->bus_dead || !host->bus_ops->sw_reset) {
+		mmc_bus_put(host);
+		return -EOPNOTSUPP;
+	}
+
+	ret = host->bus_ops->sw_reset(host);
+	mmc_bus_put(host);
+
+	if (ret)
+		pr_warn("%s: tried to SW reset card, got error %d\n",
+			mmc_hostname(host), ret);
+
+	return ret;
+}
+EXPORT_SYMBOL(mmc_sw_reset);
+
 static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
 {
 	host->f_init = freq;
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index 367ed11..a141ec0 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -33,6 +33,7 @@ struct mmc_bus_ops {
 	int (*alive)(struct mmc_host *);
 	int (*shutdown)(struct mmc_host *);
 	int (*hw_reset)(struct mmc_host *);
+	int (*sw_reset)(struct mmc_host *);
 };
 
 void mmc_attach_bus(struct mmc_host *host, const struct mmc_bus_ops *ops);