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 0b4c2ed22bce..da6bd95fa4bb 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 b74e6f14b3ac..7adc30da8366 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;