mmc: core: add eMMC hardware reset support

eMMC's may have a hardware reset line.  This patch provides a
host controller operation to implement hardware reset and
a function to reset and reinitialize the card.  Also, for MMC,
the reset is always performed before initialization.

The host must set the new host capability MMC_CAP_HW_RESET
to enable hardware reset.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

2 files changed, 97 insertions, 1 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 0b4c2ed22bc..da6bd95fa4b 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1776,6 +1776,94 @@ int mmc_set_blocklen(struct mmc_card *card, unsigned int blocklen)
 }
 EXPORT_SYMBOL(mmc_set_blocklen);
 
+static void mmc_hw_reset_for_init(struct mmc_host *host)
+{
+	if (!(host->caps & MMC_CAP_HW_RESET) || !host->ops->hw_reset)
+		return;
+	mmc_host_clk_hold(host);
+	host->ops->hw_reset(host);
+	mmc_host_clk_release(host);
+}
+
+int mmc_can_reset(struct mmc_card *card)
+{
+	u8 rst_n_function;
+
+	if (!mmc_card_mmc(card))
+		return 0;
+	rst_n_function = card->ext_csd.rst_n_function;
+	if ((rst_n_function & EXT_CSD_RST_N_EN_MASK) != EXT_CSD_RST_N_ENABLED)
+		return 0;
+	return 1;
+}
+EXPORT_SYMBOL(mmc_can_reset);
+
+static int mmc_do_hw_reset(struct mmc_host *host, int check)
+{
+	struct mmc_card *card = host->card;
+
+	if (!host->bus_ops->power_restore)
+		return -EOPNOTSUPP;
+
+	if (!(host->caps & MMC_CAP_HW_RESET) || !host->ops->hw_reset)
+		return -EOPNOTSUPP;
+
+	if (!card)
+		return -EINVAL;
+
+	if (!mmc_can_reset(card))
+		return -EOPNOTSUPP;
+
+	mmc_host_clk_hold(host);
+	mmc_set_clock(host, host->f_init);
+
+	host->ops->hw_reset(host);
+
+	/* If the reset has happened, then a status command will fail */
+	if (check) {
+		struct mmc_command cmd = {0};
+		int err;
+
+		cmd.opcode = MMC_SEND_STATUS;
+		if (!mmc_host_is_spi(card->host))
+			cmd.arg = card->rca << 16;
+		cmd.flags = MMC_RSP_SPI_R2 | MMC_RSP_R1 | MMC_CMD_AC;
+		err = mmc_wait_for_cmd(card->host, &cmd, 0);
+		if (!err) {
+			mmc_host_clk_release(host);
+			return -ENOSYS;
+		}
+	}
+
+	host->card->state &= ~(MMC_STATE_HIGHSPEED | MMC_STATE_HIGHSPEED_DDR);
+	if (mmc_host_is_spi(host)) {
+		host->ios.chip_select = MMC_CS_HIGH;
+		host->ios.bus_mode = MMC_BUSMODE_PUSHPULL;
+	} else {
+		host->ios.chip_select = MMC_CS_DONTCARE;
+		host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
+	}
+	host->ios.bus_width = MMC_BUS_WIDTH_1;
+	host->ios.timing = MMC_TIMING_LEGACY;
+	mmc_set_ios(host);
+
+	mmc_host_clk_release(host);
+
+	return host->bus_ops->power_restore(host);
+}
+
+int mmc_hw_reset(struct mmc_host *host)
+{
+	return mmc_do_hw_reset(host, 0);
+}
+EXPORT_SYMBOL(mmc_hw_reset);
+
+int mmc_hw_reset_check(struct mmc_host *host)
+{
+	return mmc_do_hw_reset(host, 1);
+}
+EXPORT_SYMBOL(mmc_hw_reset_check);
+
 static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
 {
 	host->f_init = freq;
@@ -1787,6 +1875,12 @@ static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
 	mmc_power_up(host);
 
 	/*
+	 * Some eMMCs (with VCCQ always on) may not be reset after power up, so
+	 * do a hardware reset if possible.
+	 */
+	mmc_hw_reset_for_init(host);
+
+	/*
 	 * sdio_reset sends CMD52 to reset card.  Since we do not know
 	 * if the card is being re-initialized, just send it.  CMD52
 	 * should be ignored by SD/eMMC cards.
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index b74e6f14b3a..7adc30da836 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -402,8 +402,10 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
 			ext_csd[EXT_CSD_TRIM_MULT];
 	}
 
-	if (card->ext_csd.rev >= 5)
+	if (card->ext_csd.rev >= 5) {
 		card->ext_csd.rel_param = ext_csd[EXT_CSD_WR_REL_PARAM];
+		card->ext_csd.rst_n_function = ext_csd[EXT_CSD_RST_N_FUNCTION];
+	}
 
 	if (ext_csd[EXT_CSD_ERASED_MEM_CONT])
 		card->erased_byte = 0xFF;