[PATCH v3] mmc: dw_mmc: add hw_reset support

[Shawn Lin <shawn.lin@rock-chips.com>]

This patch implement hw_reset function for DesignWare
MMC controller. By adding this feature, mmc blk can
do some basic recovery.

Set the following resets:
software reset – BMOD[0] for IDMAC only
DMA reset– CTRL[2]
FIFO reset – CTRL[1] bits

Program the CARD_RESET register with a value of 0 for the bit
corresponding to the card number; This programming asserts the
RST_n signal and resets the card. After a minimum of 1 μs, de-asserts the
RST_n signal and takes the card out of reset. The application can program
a new CMD only after a minimum of 200 us

This implementation can be easily tested by cutting off->On vmmc
while doing data accessing in background to simulate that case.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>

---

Changes in v3:
- reset for each slot
- simply the commit msg

Changes in v2:
- remove unecessary mb
- reduce time cost for hw_reset
- combine SDMMC_CTRL_DMA_RESET and SDMMC_CTRL_FIFO_RESET

 drivers/mmc/host/dw_mmc.c | 29 +++++++++++++++++++++++++++++
 drivers/mmc/host/dw_mmc.h |  3 +++
 2 files changed, 32 insertions(+)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 7128351..fddbcb6 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -1477,6 +1477,34 @@ static int dw_mci_get_cd(struct mmc_host *mmc)
 	return present;
 }
 
+static void dw_mci_hw_reset(struct mmc_host *mmc)
+{
+	struct dw_mci_slot *slot = mmc_priv(mmc);
+	struct dw_mci *host = slot->host;
+	int reset;
+
+	if (host->use_dma == TRANS_MODE_IDMAC)
+		dw_mci_idmac_reset(host);
+
+	if (!dw_mci_ctrl_reset(host, SDMMC_CTRL_DMA_RESET |
+				     SDMMC_CTRL_FIFO_RESET))
+		return;
+
+	/*
+	 * According to eMMC spec, card reset procedure:
+	 * tRstW >= 1us:   RST_n pulse width
+	 * tRSCA >= 200us: RST_n to Command time
+	 * tRSTH >= 1us:   RST_n high period
+	 */
+	reset = mci_readl(host, RST_N);
+	reset &= ~(SDMMC_RST_HWACTIVE << slot->id);
+	mci_writel(slot->host, RST_N, reset);
+	usleep_range(1, 2);
+	reset |= SDMMC_RST_HWACTIVE << slot->id;
+	mci_writel(slot->host, RST_N, reset);
+	usleep_range(200, 300);
+}
+
 static void dw_mci_init_card(struct mmc_host *mmc, struct mmc_card *card)
 {
 	struct dw_mci_slot *slot = mmc_priv(mmc);
@@ -1563,6 +1591,7 @@ static const struct mmc_host_ops dw_mci_ops = {
 	.set_ios		= dw_mci_set_ios,
 	.get_ro			= dw_mci_get_ro,
 	.get_cd			= dw_mci_get_cd,
+	.hw_reset               = dw_mci_hw_reset,
 	.enable_sdio_irq	= dw_mci_enable_sdio_irq,
 	.execute_tuning		= dw_mci_execute_tuning,
 	.card_busy		= dw_mci_card_busy,
diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
index f695b58..a14b7fc 100644
--- a/drivers/mmc/host/dw_mmc.h
+++ b/drivers/mmc/host/dw_mmc.h
@@ -46,6 +46,7 @@
 #define SDMMC_VERID		0x06c
 #define SDMMC_HCON		0x070
 #define SDMMC_UHS_REG		0x074
+#define SDMMC_RST_N		0x078
 #define SDMMC_BMOD		0x080
 #define SDMMC_PLDMND		0x084
 #define SDMMC_DBADDR		0x088
@@ -169,6 +170,8 @@
 #define SDMMC_IDMAC_ENABLE		BIT(7)
 #define SDMMC_IDMAC_FB			BIT(1)
 #define SDMMC_IDMAC_SWRESET		BIT(0)
+/* H/W reset */
+#define SDMMC_RST_HWACTIVE		0x1
 /* Version ID register define */
 #define SDMMC_GET_VERID(x)		((x) & 0xFFFF)
 /* Card read threshold */
-- 
2.3.7