Message-Id: <20190916154546.24982-6-manivannan.sadhasivam@linaro.org>
Date:   Mon, 16 Sep 2019 21:15:44 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     ulf.hansson@...aro.org, afaerber@...e.de, robh+dt@...nel.org,
        sboyd@...nel.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        thomas.liau@...ions-semi.com, linux-actions@...ts.infradead.org,
        linus.walleij@...aro.org, linux-clk@...r.kernel.org,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH v4 5/7] mmc: Add Actions Semi Owl SoCs SD/MMC driver

Add SD/MMC driver for Actions Semi Owl SoCs. This driver currently
supports standard, high speed, SDR12, SDR25 and SDR50. DDR50 mode is
supported but it is untested. There is no SDIO support for now.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/mmc/host/Kconfig   |   8 +
 drivers/mmc/host/Makefile  |   1 +
 drivers/mmc/host/owl-mmc.c | 696 +++++++++++++++++++++++++++++++++++++
 3 files changed, 705 insertions(+)
 create mode 100644 drivers/mmc/host/owl-mmc.c

diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
index 14d89a108edd..2c38e36953af 100644
--- a/drivers/mmc/host/Kconfig
+++ b/drivers/mmc/host/Kconfig
@@ -1006,3 +1006,11 @@ config MMC_SDHCI_AM654
 	  If you have a controller with this interface, say Y or M here.
 
 	  If unsure, say N.
+
+config MMC_OWL
+	tristate "Actions Semi Owl SD/MMC Host Controller support"
+	depends on HAS_DMA
+	depends on ARCH_ACTIONS || COMPILE_TEST
+	help
+	  This selects support for the SD/MMC Host Controller on
+	  Actions Semi Owl SoCs.
diff --git a/drivers/mmc/host/Makefile b/drivers/mmc/host/Makefile
index 73578718f119..41a0b1728389 100644
--- a/drivers/mmc/host/Makefile
+++ b/drivers/mmc/host/Makefile
@@ -73,6 +73,7 @@ obj-$(CONFIG_MMC_SUNXI)		+= sunxi-mmc.o
 obj-$(CONFIG_MMC_USDHI6ROL0)	+= usdhi6rol0.o
 obj-$(CONFIG_MMC_TOSHIBA_PCI)	+= toshsd.o
 obj-$(CONFIG_MMC_BCM2835)	+= bcm2835.o
+obj-$(CONFIG_MMC_OWL)		+= owl-mmc.o
 
 obj-$(CONFIG_MMC_REALTEK_PCI)	+= rtsx_pci_sdmmc.o
 obj-$(CONFIG_MMC_REALTEK_USB)	+= rtsx_usb_sdmmc.o
diff --git a/drivers/mmc/host/owl-mmc.c b/drivers/mmc/host/owl-mmc.c
new file mode 100644
index 000000000000..771e3d00f1bb
--- /dev/null
+++ b/drivers/mmc/host/owl-mmc.c
@@ -0,0 +1,696 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Actions Semi Owl SoCs SD/MMC driver
+ *
+ * Copyright (c) 2014 Actions Semi Inc.
+ * Copyright (c) 2019 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
+ *
+ * TODO: SDIO support
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-direction.h>
+#include <linux/dma-mapping.h>
+#include <linux/interrupt.h>
+#include <linux/mmc/host.h>
+#include <linux/mmc/slot-gpio.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/reset.h>
+#include <linux/spinlock.h>
+
+/*
+ * SDC registers
+ */
+#define OWL_REG_SD_EN			0x0000
+#define OWL_REG_SD_CTL			0x0004
+#define OWL_REG_SD_STATE		0x0008
+#define OWL_REG_SD_CMD			0x000c
+#define OWL_REG_SD_ARG			0x0010
+#define OWL_REG_SD_RSPBUF0		0x0014
+#define OWL_REG_SD_RSPBUF1		0x0018
+#define OWL_REG_SD_RSPBUF2		0x001c
+#define OWL_REG_SD_RSPBUF3		0x0020
+#define OWL_REG_SD_RSPBUF4		0x0024
+#define OWL_REG_SD_DAT			0x0028
+#define OWL_REG_SD_BLK_SIZE		0x002c
+#define OWL_REG_SD_BLK_NUM		0x0030
+#define OWL_REG_SD_BUF_SIZE		0x0034
+
+/* SD_EN Bits */
+#define OWL_SD_EN_RANE			BIT(31)
+#define OWL_SD_EN_RAN_SEED(x)		(((x) & 0x3f) << 24)
+#define OWL_SD_EN_S18EN			BIT(12)
+#define OWL_SD_EN_RESE			BIT(10)
+#define OWL_SD_EN_DAT1_S		BIT(9)
+#define OWL_SD_EN_CLK_S			BIT(8)
+#define OWL_SD_ENABLE			BIT(7)
+#define OWL_SD_EN_BSEL			BIT(6)
+#define OWL_SD_EN_SDIOEN		BIT(3)
+#define OWL_SD_EN_DDREN			BIT(2)
+#define OWL_SD_EN_DATAWID(x)		(((x) & 0x3) << 0)
+
+/* SD_CTL Bits */
+#define OWL_SD_CTL_TOUTEN		BIT(31)
+#define OWL_SD_CTL_TOUTCNT(x)		(((x) & 0x7f) << 24)
+#define OWL_SD_CTL_DELAY_MSK		GENMASK(23, 16)
+#define OWL_SD_CTL_RDELAY(x)		(((x) & 0xf) << 20)
+#define OWL_SD_CTL_WDELAY(x)		(((x) & 0xf) << 16)
+#define OWL_SD_CTL_CMDLEN		BIT(13)
+#define OWL_SD_CTL_SCC			BIT(12)
+#define OWL_SD_CTL_TCN(x)		(((x) & 0xf) << 8)
+#define OWL_SD_CTL_TS			BIT(7)
+#define OWL_SD_CTL_LBE			BIT(6)
+#define OWL_SD_CTL_C7EN			BIT(5)
+#define OWL_SD_CTL_TM(x)		(((x) & 0xf) << 0)
+
+#define OWL_SD_DELAY_LOW_CLK		0x0f
+#define OWL_SD_DELAY_MID_CLK		0x0a
+#define OWL_SD_DELAY_HIGH_CLK		0x09
+#define OWL_SD_RDELAY_DDR50		0x0a
+#define OWL_SD_WDELAY_DDR50		0x08
+
+/* SD_STATE Bits */
+#define OWL_SD_STATE_DAT1BS		BIT(18)
+#define OWL_SD_STATE_SDIOB_P		BIT(17)
+#define OWL_SD_STATE_SDIOB_EN		BIT(16)
+#define OWL_SD_STATE_TOUTE		BIT(15)
+#define OWL_SD_STATE_BAEP		BIT(14)
+#define OWL_SD_STATE_MEMRDY		BIT(12)
+#define OWL_SD_STATE_CMDS		BIT(11)
+#define OWL_SD_STATE_DAT1AS		BIT(10)
+#define OWL_SD_STATE_SDIOA_P		BIT(9)
+#define OWL_SD_STATE_SDIOA_EN		BIT(8)
+#define OWL_SD_STATE_DAT0S		BIT(7)
+#define OWL_SD_STATE_TEIE		BIT(6)
+#define OWL_SD_STATE_TEI		BIT(5)
+#define OWL_SD_STATE_CLNR		BIT(4)
+#define OWL_SD_STATE_CLC		BIT(3)
+#define OWL_SD_STATE_WC16ER		BIT(2)
+#define OWL_SD_STATE_RC16ER		BIT(1)
+#define OWL_SD_STATE_CRC7ER		BIT(0)
+
+struct owl_mmc_host {
+	struct device *dev;
+	struct reset_control *reset;
+	void __iomem *base;
+	struct clk *clk;
+	struct completion sdc_complete;
+	spinlock_t lock;
+	int irq;
+	u32 clock;
+	bool ddr_50;
+
+	enum dma_data_direction dma_dir;
+	struct dma_chan *dma;
+	struct dma_async_tx_descriptor *desc;
+	struct dma_slave_config dma_cfg;
+	struct completion dma_complete;
+
+	struct mmc_host	*mmc;
+	struct mmc_request *mrq;
+	struct mmc_command *cmd;
+	struct mmc_data	*data;
+};
+
+static void owl_mmc_update_reg(void __iomem *reg, unsigned int val, bool state)
+{
+	unsigned int regval;
+
+	regval = readl(reg);
+
+	if (state)
+		regval |= val;
+	else
+		regval &= ~val;
+
+	writel(regval, reg);
+}
+
+static irqreturn_t owl_irq_handler(int irq, void *devid)
+{
+	struct owl_mmc_host *owl_host = devid;
+	unsigned long flags;
+	u32 state;
+
+	spin_lock_irqsave(&owl_host->lock, flags);
+
+	state = readl(owl_host->base + OWL_REG_SD_STATE);
+	if (state & OWL_SD_STATE_TEI) {
+		state = readl(owl_host->base + OWL_REG_SD_STATE);
+		state |= OWL_SD_STATE_TEI;
+		writel(state, owl_host->base + OWL_REG_SD_STATE);
+		complete(&owl_host->sdc_complete);
+	}
+
+	spin_unlock_irqrestore(&owl_host->lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+static void owl_mmc_finish_request(struct owl_mmc_host *owl_host)
+{
+	struct mmc_request *mrq = owl_host->mrq;
+	struct mmc_data *data = mrq->data;
+
+	/* Should never be NULL */
+	WARN_ON(!mrq);
+
+	owl_host->mrq = NULL;
+
+	if (data)
+		dma_unmap_sg(owl_host->dma->device->dev, data->sg, data->sg_len,
+			     owl_host->dma_dir);
+
+	/* Finally finish request */
+	mmc_request_done(owl_host->mmc, mrq);
+}
+
+static void owl_mmc_send_cmd(struct owl_mmc_host *owl_host,
+			     struct mmc_command *cmd,
+			     struct mmc_data *data)
+{
+	u32 mode, state, resp[2];
+	u32 cmd_rsp_mask = 0;
+
+	init_completion(&owl_host->sdc_complete);
+
+	switch (mmc_resp_type(cmd)) {
+	case MMC_RSP_NONE:
+		mode = OWL_SD_CTL_TM(0);
+		break;
+
+	case MMC_RSP_R1:
+		if (data) {
+			if (data->flags & MMC_DATA_READ)
+				mode = OWL_SD_CTL_TM(4);
+			else
+				mode = OWL_SD_CTL_TM(5);
+		} else {
+			mode = OWL_SD_CTL_TM(1);
+		}
+		cmd_rsp_mask = OWL_SD_STATE_CLNR | OWL_SD_STATE_CRC7ER;
+
+		break;
+
+	case MMC_RSP_R1B:
+		mode = OWL_SD_CTL_TM(3);
+		cmd_rsp_mask = OWL_SD_STATE_CLNR | OWL_SD_STATE_CRC7ER;
+		break;
+
+	case MMC_RSP_R2:
+		mode = OWL_SD_CTL_TM(2);
+		cmd_rsp_mask = OWL_SD_STATE_CLNR | OWL_SD_STATE_CRC7ER;
+		break;
+
+	case MMC_RSP_R3:
+		mode = OWL_SD_CTL_TM(1);
+		cmd_rsp_mask = OWL_SD_STATE_CLNR;
+		break;
+
+	default:
+		dev_warn(owl_host->dev, "Unknown MMC command\n");
+		cmd->error = -EINVAL;
+		return;
+	}
+
+	/* Keep current WDELAY and RDELAY */
+	mode |= (readl(owl_host->base + OWL_REG_SD_CTL) & (0xff << 16));
+
+	/* Start to send corresponding command type */
+	writel(cmd->arg, owl_host->base + OWL_REG_SD_ARG);
+	writel(cmd->opcode, owl_host->base + OWL_REG_SD_CMD);
+
+	/* Set LBE to send clk at the end of last read block */
+	if (data) {
+		mode |= (OWL_SD_CTL_TS | OWL_SD_CTL_LBE | 0x64000000);
+	} else {
+		mode &= ~(OWL_SD_CTL_TOUTEN | OWL_SD_CTL_LBE);
+		mode |= OWL_SD_CTL_TS;
+	}
+
+	owl_host->cmd = cmd;
+
+	/* Start transfer */
+	writel(mode, owl_host->base + OWL_REG_SD_CTL);
+
+	if (data)
+		return;
+
+	if (!wait_for_completion_timeout(&owl_host->sdc_complete, 30 * HZ)) {
+		dev_err(owl_host->dev, "CMD interrupt timeout\n");
+		cmd->error = -ETIMEDOUT;
+		return;
+	}
+
+	state = readl(owl_host->base + OWL_REG_SD_STATE);
+	if (mmc_resp_type(cmd) & MMC_RSP_PRESENT) {
+		if (cmd_rsp_mask & state) {
+			if (state & OWL_SD_STATE_CLNR) {
+				dev_err(owl_host->dev, "Error CMD_NO_RSP\n");
+				cmd->error = -EILSEQ;
+				return;
+			}
+
+			if (state & OWL_SD_STATE_CRC7ER) {
+				dev_err(owl_host->dev, "Error CMD_RSP_CRC\n");
+				cmd->error = -EILSEQ;
+				return;
+			}
+		}
+
+		if (mmc_resp_type(cmd) & MMC_RSP_136) {
+			cmd->resp[3] = readl(owl_host->base + OWL_REG_SD_RSPBUF0);
+			cmd->resp[2] = readl(owl_host->base + OWL_REG_SD_RSPBUF1);
+			cmd->resp[1] = readl(owl_host->base + OWL_REG_SD_RSPBUF2);
+			cmd->resp[0] = readl(owl_host->base + OWL_REG_SD_RSPBUF3);
+		} else {
+			resp[0] = readl(owl_host->base + OWL_REG_SD_RSPBUF0);
+			resp[1] = readl(owl_host->base + OWL_REG_SD_RSPBUF1);
+			cmd->resp[0] = resp[1] << 24 | resp[0] >> 8;
+			cmd->resp[1] = resp[1] >> 8;
+		}
+	}
+}
+
+static void owl_mmc_dma_complete(void *param)
+{
+	struct owl_mmc_host *owl_host = param;
+	struct mmc_data *data = owl_host->data;
+
+	if (data)
+		complete(&owl_host->dma_complete);
+}
+
+static int owl_mmc_prepare_data(struct owl_mmc_host *owl_host,
+				struct mmc_data *data)
+{
+	u32 total;
+
+	owl_mmc_update_reg(owl_host->base + OWL_REG_SD_EN, OWL_SD_EN_BSEL,
+			   true);
+	writel(data->blocks, owl_host->base + OWL_REG_SD_BLK_NUM);
+	writel(data->blksz, owl_host->base + OWL_REG_SD_BLK_SIZE);
+	total = data->blksz * data->blocks;
+
+	if (total < 512)
+		writel(total, owl_host->base + OWL_REG_SD_BUF_SIZE);
+	else
+		writel(512, owl_host->base + OWL_REG_SD_BUF_SIZE);
+
+	if (data->flags & MMC_DATA_WRITE) {
+		owl_host->dma_dir = DMA_TO_DEVICE;
+		owl_host->dma_cfg.direction = DMA_MEM_TO_DEV;
+	} else {
+		owl_host->dma_dir = DMA_FROM_DEVICE;
+		owl_host->dma_cfg.direction = DMA_DEV_TO_MEM;
+	}
+
+	dma_map_sg(owl_host->dma->device->dev, data->sg,
+		   data->sg_len, owl_host->dma_dir);
+
+	dmaengine_slave_config(owl_host->dma, &owl_host->dma_cfg);
+	owl_host->desc = dmaengine_prep_slave_sg(owl_host->dma, data->sg,
+						 data->sg_len,
+						 owl_host->dma_cfg.direction,
+						 DMA_PREP_INTERRUPT |
+						 DMA_CTRL_ACK);
+	if (!owl_host->desc) {
+		dev_err(owl_host->dev, "Can't prepare slave sg\n");
+		return -EBUSY;
+	}
+
+	owl_host->data = data;
+
+	owl_host->desc->callback = owl_mmc_dma_complete;
+	owl_host->desc->callback_param = (void *)owl_host;
+	data->error = 0;
+
+	return 0;
+}
+
+static void owl_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
+{
+	struct owl_mmc_host *owl_host = mmc_priv(mmc);
+	struct mmc_data *data = mrq->data;
+	int ret;
+
+	owl_host->mrq = mrq;
+	if (mrq->data) {
+		ret = owl_mmc_prepare_data(owl_host, data);
+		if (ret < 0) {
+			data->error = ret;
+			goto err_out;
+		}
+
+		init_completion(&owl_host->dma_complete);
+		dmaengine_submit(owl_host->desc);
+		dma_async_issue_pending(owl_host->dma);
+	}
+
+	owl_mmc_send_cmd(owl_host, mrq->cmd, data);
+
+	if (data) {
+		if (!wait_for_completion_timeout(&owl_host->sdc_complete,
+						 10 * HZ)) {
+			dev_err(owl_host->dev, "CMD interrupt timeout\n");
+			mrq->cmd->error = -ETIMEDOUT;
+			dmaengine_terminate_all(owl_host->dma);
+			goto err_out;
+		}
+
+		if (!wait_for_completion_timeout(&owl_host->dma_complete,
+						 5 * HZ)) {
+			dev_err(owl_host->dev, "DMA interrupt timeout\n");
+			mrq->cmd->error = -ETIMEDOUT;
+			dmaengine_terminate_all(owl_host->dma);
+			goto err_out;
+		}
+
+		if (data->stop)
+			owl_mmc_send_cmd(owl_host, data->stop, NULL);
+
+		data->bytes_xfered = data->blocks * data->blksz;
+	}
+
+err_out:
+	owl_mmc_finish_request(owl_host);
+}
+
+static int owl_mmc_set_clk_rate(struct owl_mmc_host *owl_host,
+				unsigned int rate)
+{
+	unsigned long clk_rate;
+	int ret;
+	u32 reg;
+
+	reg = readl(owl_host->base + OWL_REG_SD_CTL);
+	reg &= ~OWL_SD_CTL_DELAY_MSK;
+
+	/* Set RDELAY and WDELAY based on the clock */
+	if (rate <= 1000000) {
+		writel(reg | OWL_SD_CTL_RDELAY(OWL_SD_DELAY_LOW_CLK) |
+		       OWL_SD_CTL_WDELAY(OWL_SD_DELAY_LOW_CLK),
+		       owl_host->base + OWL_REG_SD_CTL);
+	} else if ((rate > 1000000) && (rate <= 26000000)) {
+		writel(reg | OWL_SD_CTL_RDELAY(OWL_SD_DELAY_MID_CLK) |
+		       OWL_SD_CTL_WDELAY(OWL_SD_DELAY_MID_CLK),
+		       owl_host->base + OWL_REG_SD_CTL);
+	} else if ((rate > 26000000) && (rate <= 52000000) && !owl_host->ddr_50) {
+		writel(reg | OWL_SD_CTL_RDELAY(OWL_SD_DELAY_HIGH_CLK) |
+		       OWL_SD_CTL_WDELAY(OWL_SD_DELAY_HIGH_CLK),
+		       owl_host->base + OWL_REG_SD_CTL);
+	/* DDR50 mode has special delay chain */
+	} else if ((rate > 26000000) && (rate <= 52000000) && owl_host->ddr_50) {
+		writel(reg | OWL_SD_CTL_RDELAY(OWL_SD_RDELAY_DDR50) |
+		       OWL_SD_CTL_WDELAY(OWL_SD_WDELAY_DDR50),
+		       owl_host->base + OWL_REG_SD_CTL);
+	} else {
+		dev_err(owl_host->dev, "SD clock rate not supported\n");
+		return -EINVAL;
+	}
+
+	clk_rate = clk_round_rate(owl_host->clk, rate << 1);
+	ret = clk_set_rate(owl_host->clk, clk_rate);
+
+	return ret;
+}
+
+static void owl_mmc_set_clk(struct owl_mmc_host *owl_host, struct mmc_ios *ios)
+{
+	if (!ios->clock)
+		return;
+
+	owl_host->clock = ios->clock;
+	owl_mmc_set_clk_rate(owl_host, ios->clock);
+}
+
+static void owl_mmc_set_bus_width(struct owl_mmc_host *owl_host,
+				  struct mmc_ios *ios)
+{
+	u32 reg;
+
+	reg = readl(owl_host->base + OWL_REG_SD_EN);
+	reg &= ~0x03;
+	switch (ios->bus_width) {
+	case MMC_BUS_WIDTH_1:
+		break;
+	case MMC_BUS_WIDTH_4:
+		reg |= OWL_SD_EN_DATAWID(1);
+		break;
+	case MMC_BUS_WIDTH_8:
+		reg |= OWL_SD_EN_DATAWID(2);
+		break;
+	}
+
+	writel(reg, owl_host->base + OWL_REG_SD_EN);
+}
+
+static void owl_mmc_ctr_reset(struct owl_mmc_host *owl_host)
+{
+	reset_control_assert(owl_host->reset);
+	udelay(20);
+	reset_control_deassert(owl_host->reset);
+}
+
+static void owl_mmc_power_on(struct owl_mmc_host *owl_host)
+{
+	u32 mode;
+
+	init_completion(&owl_host->sdc_complete);
+
+	/* Enable transfer end IRQ */
+	owl_mmc_update_reg(owl_host->base + OWL_REG_SD_STATE,
+		       OWL_SD_STATE_TEIE, true);
+
+	/* Send init clk */
+	mode = (readl(owl_host->base + OWL_REG_SD_CTL) & (0xff << 16));
+	mode |= OWL_SD_CTL_TS | OWL_SD_CTL_TCN(5) | OWL_SD_CTL_TM(8);
+	writel(mode, owl_host->base + OWL_REG_SD_CTL);
+
+	if (!wait_for_completion_timeout(&owl_host->sdc_complete, HZ)) {
+		dev_err(owl_host->dev, "CMD interrupt timeout\n");
+		return;
+	}
+}
+
+static void owl_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
+{
+	struct owl_mmc_host *owl_host = mmc_priv(mmc);
+
+	switch (ios->power_mode) {
+	case MMC_POWER_UP:
+		dev_dbg(owl_host->dev, "Powering card up\n");
+
+		/* Reset the SDC controller to clear all previous states */
+		owl_mmc_ctr_reset(owl_host);
+		clk_prepare_enable(owl_host->clk);
+		writel(OWL_SD_ENABLE | OWL_SD_EN_RESE,
+		       owl_host->base + OWL_REG_SD_EN);
+
+		break;
+
+	case MMC_POWER_ON:
+		dev_dbg(owl_host->dev, "Powering card on\n");
+		owl_mmc_power_on(owl_host);
+
+		break;
+
+	case MMC_POWER_OFF:
+		dev_dbg(owl_host->dev, "Powering card off\n");
+		clk_disable_unprepare(owl_host->clk);
+
+		return;
+
+	default:
+		dev_dbg(owl_host->dev, "Ignoring unknown card power state\n");
+		break;
+	}
+
+	if (ios->clock != owl_host->clock)
+		owl_mmc_set_clk(owl_host, ios);
+
+	owl_mmc_set_bus_width(owl_host, ios);
+
+	/* Enable DDR mode if requested */
+	if (ios->timing == MMC_TIMING_UHS_DDR50) {
+		owl_host->ddr_50 = 1;
+		owl_mmc_update_reg(owl_host->base + OWL_REG_SD_EN,
+			       OWL_SD_EN_DDREN, true);
+	} else {
+		owl_host->ddr_50 = 0;
+	}
+}
+
+static int owl_mmc_start_signal_voltage_switch(struct mmc_host *mmc,
+					       struct mmc_ios *ios)
+{
+	struct owl_mmc_host *owl_host = mmc_priv(mmc);
+
+	/* It is enough to change the pad ctrl bit for voltage switch */
+	switch (ios->signal_voltage) {
+	case MMC_SIGNAL_VOLTAGE_330:
+		owl_mmc_update_reg(owl_host->base + OWL_REG_SD_EN,
+			       OWL_SD_EN_S18EN, false);
+		break;
+	case MMC_SIGNAL_VOLTAGE_180:
+		owl_mmc_update_reg(owl_host->base + OWL_REG_SD_EN,
+			       OWL_SD_EN_S18EN, true);
+		break;
+	default:
+		return -ENOTSUPP;
+	}
+
+	return 0;
+}
+
+static const struct mmc_host_ops owl_mmc_ops = {
+	.request	= owl_mmc_request,
+	.set_ios	= owl_mmc_set_ios,
+	.get_ro		= mmc_gpio_get_ro,
+	.get_cd		= mmc_gpio_get_cd,
+	.start_signal_voltage_switch = owl_mmc_start_signal_voltage_switch,
+};
+
+static int owl_mmc_probe(struct platform_device *pdev)
+{
+	struct owl_mmc_host *owl_host;
+	struct mmc_host *mmc;
+	struct resource *res;
+	int ret;
+
+	mmc = mmc_alloc_host(sizeof(struct owl_mmc_host), &pdev->dev);
+	if (!mmc) {
+		dev_err(&pdev->dev, "mmc alloc host failed\n");
+		return -ENOMEM;
+	}
+	platform_set_drvdata(pdev, mmc);
+
+	owl_host = mmc_priv(mmc);
+	owl_host->dev = &pdev->dev;
+	owl_host->mmc = mmc;
+	spin_lock_init(&owl_host->lock);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	owl_host->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(owl_host->base)) {
+		dev_err(&pdev->dev, "Failed to remap registers\n");
+		ret = PTR_ERR(owl_host->base);
+		goto err_free_host;
+	}
+
+	owl_host->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(owl_host->clk)) {
+		dev_err(&pdev->dev, "No clock defined\n");
+		ret = PTR_ERR(owl_host->clk);
+		goto err_free_host;
+	}
+
+	owl_host->reset = devm_reset_control_get_exclusive(&pdev->dev, NULL);
+	if (IS_ERR(owl_host->reset)) {
+		dev_err(&pdev->dev, "Could not get reset control\n");
+		ret = PTR_ERR(owl_host->reset);
+		goto err_free_host;
+	}
+
+	mmc->ops		= &owl_mmc_ops;
+	mmc->max_blk_count	= 512;
+	mmc->max_blk_size	= 512;
+	mmc->max_segs		= 256;
+	mmc->max_seg_size	= 262144;
+	mmc->max_req_size	= 262144;
+	/* 100kHz ~ 52MHz */
+	mmc->f_min		= 100000;
+	mmc->f_max		= 52000000;
+	mmc->caps	       |= MMC_CAP_MMC_HIGHSPEED | MMC_CAP_SD_HIGHSPEED |
+				  MMC_CAP_4_BIT_DATA;
+	mmc->caps2		= (MMC_CAP2_BOOTPART_NOACC | MMC_CAP2_NO_SDIO);
+	mmc->ocr_avail		= MMC_VDD_32_33 | MMC_VDD_33_34 |
+				  MMC_VDD_165_195;
+
+	ret = mmc_of_parse(mmc);
+	if (ret)
+		goto err_free_host;
+
+	pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
+	pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
+	owl_host->dma = dma_request_slave_channel(&pdev->dev, "mmc");
+	if (!owl_host->dma) {
+		dev_err(owl_host->dev, "Failed to get external DMA channel.\n");
+		ret = -ENXIO;
+		goto err_free_host;
+	}
+
+	dev_info(&pdev->dev, "Using %s for DMA transfers\n",
+		 dma_chan_name(owl_host->dma));
+
+	owl_host->dma_cfg.src_addr = res->start + OWL_REG_SD_DAT;
+	owl_host->dma_cfg.dst_addr = res->start + OWL_REG_SD_DAT;
+	owl_host->dma_cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+	owl_host->dma_cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+	owl_host->dma_cfg.device_fc = false;
+
+	owl_host->irq = platform_get_irq(pdev, 0);
+	if (owl_host->irq < 0) {
+		ret = -EINVAL;
+		goto err_free_host;
+	}
+
+	ret = devm_request_irq(&pdev->dev, owl_host->irq, owl_irq_handler,
+			       0, dev_name(&pdev->dev), owl_host);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to request irq %d\n",
+			owl_host->irq);
+		goto err_free_host;
+	}
+
+	ret = mmc_add_host(mmc);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to add host\n");
+		goto err_free_host;
+	}
+
+	dev_dbg(&pdev->dev, "Owl MMC Controller Initialized\n");
+
+	return 0;
+
+err_free_host:
+	mmc_free_host(mmc);
+
+	return ret;
+}
+
+static int owl_mmc_remove(struct platform_device *pdev)
+{
+	struct mmc_host	*mmc = platform_get_drvdata(pdev);
+	struct owl_mmc_host *owl_host = mmc_priv(mmc);
+
+	mmc_remove_host(mmc);
+	disable_irq(owl_host->irq);
+	mmc_free_host(mmc);
+
+	return 0;
+}
+
+static const struct of_device_id owl_mmc_of_match[] = {
+	{.compatible = "actions,owl-mmc",},
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, owl_mmc_of_match);
+
+static struct platform_driver owl_mmc_driver = {
+	.driver = {
+		.name	= "owl_mmc",
+		.of_match_table = of_match_ptr(owl_mmc_of_match),
+	},
+	.probe		= owl_mmc_probe,
+	.remove		= owl_mmc_remove,
+};
+module_platform_driver(owl_mmc_driver);
+
+MODULE_DESCRIPTION("Actions Semi Owl SoCs SD/MMC Driver");
+MODULE_AUTHOR("Actions Semi");
+MODULE_AUTHOR("Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>");
+MODULE_LICENSE("GPL");
-- 
2.17.1

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