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From:   Chuanhong Guo <gch981213@gmail.com>
To:     linux-mediatek@lists.infradead.org, linux-spi@vger.kernel.org,
        linux-mtd@lists.infradead.org, devicetree@vger.kernel.org
Cc:     Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Chuanhong Guo <gch981213@gmail.com>
Subject: [PATCH 1/2] spi: add support for mediatek spi-nor controller
Date:   Sat, 15 Feb 2020 14:58:25 +0800
Message-Id: <20200215065826.739102-2-gch981213@gmail.com>
In-Reply-To: <20200215065826.739102-1-gch981213@gmail.com>
References: <20200215065826.739102-1-gch981213@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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This is a driver for mtk spi-nor controller using spi-mem interface.
The same controller already has limited support provided by mtk-quadspi
driver under spi-nor framework and this new driver is a replacement
for the old one.

Comparing to the old driver, this driver has following advantages:
1. It can handle any full-duplex spi transfer up to 6 bytes, and
   this is implemented using generic spi interface.
2. It take account into command opcode properly. The reading routine
   in this controller can only use 0x03 or 0x0b as opcode on 1-1-1
   transfers, but old driver doesn't implement this properly. This
   driver checks supported opcode explicitly and use (1) to perform
   unmatched operations.
3. It properly handles SFDP reading. Old driver can't read SFDP
   due to the bug mentioned in (2).
4. It can do 1-2-2 and 1-4-4 fast reading on spi-nor. These two ops
   requires parsing SFDP, which isn't possible in old driver. And
   the old driver is only flagged to support 1-1-2 mode.
5. It takes advantage of the DMA feature in this controller for
   long reads and supports IRQ on DMA requests to free cpu cycles
   from polling status registers on long DMA reading. It achieves
   up to 17.5MB/s reading speed (1-4-4 mode) which is way faster
   than the old one. IRQ is implemented as optional to maintain
   backward compatibility.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
---
Benefits of this driver replacement is explained in commit message,
but I'm not sure if that's a proper place for this. If it's not
desired, I could remove them in v2.

About the driver name: I initially started by prefixing everyting
with mt8173 instead of mtk, but I then saw this commit:
23bae78e8a57 ("mtd: mtk-nor: modify functions' name more generally")
and renamed everything to mtk prefixed instead.
The original name "mtk-quadspi" sounds like a generic QSPI controller,
but in reality this is a controller specifically designed for SPI-NOR
and has limited capability that doesn't make much sense for other
slave devices, so I picked spi-mtk-nor as the name for this new driver.

About IRQ: I only know IRQ number on MT7629. If I implemented IRQ as
required, all other MTK SoCs using this controller will be broken and
I won't have enough knowledge to fix them. So IRQ is implemented as
optional and register polling is used as a backup when IRQ isn't
available.

 drivers/spi/Kconfig       |  10 +
 drivers/spi/Makefile      |   1 +
 drivers/spi/spi-mtk-nor.c | 689 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 700 insertions(+)
 create mode 100644 drivers/spi/spi-mtk-nor.c

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 82177db238be..57735ca844d9 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -450,6 +450,16 @@ config SPI_MT7621
 	help
 	  This selects a driver for the MediaTek MT7621 SPI Controller.
 
+config SPI_MTK_NOR
+	tristate "MediaTek SPI NOR controller"
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	help
+	  This enables support for SPI NOR controller found on MediaTek
+	  ARM SoCs. This is a controller specifically for SPI-NOR flash.
+	  It can perform generic SPI transfers up to 6 bytes via generic
+	  SPI interface as well as several SPI-NOR specific instructions
+	  via SPI MEM interface.
+
 config SPI_NPCM_FIU
 	tristate "Nuvoton NPCM FLASH Interface Unit"
 	depends on ARCH_NPCM || COMPILE_TEST
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 74db1f2c3299..7eb3475a4520 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -64,6 +64,7 @@ obj-$(CONFIG_SPI_MPC52xx_PSC)		+= spi-mpc52xx-psc.o
 obj-$(CONFIG_SPI_MPC52xx)		+= spi-mpc52xx.o
 obj-$(CONFIG_SPI_MT65XX)                += spi-mt65xx.o
 obj-$(CONFIG_SPI_MT7621)		+= spi-mt7621.o
+obj-$(CONFIG_SPI_MTK_NOR)		+= spi-mtk-nor.o
 obj-$(CONFIG_SPI_MXIC)			+= spi-mxic.o
 obj-$(CONFIG_SPI_MXS)			+= spi-mxs.o
 obj-$(CONFIG_SPI_NPCM_FIU)		+= spi-npcm-fiu.o
diff --git a/drivers/spi/spi-mtk-nor.c b/drivers/spi/spi-mtk-nor.c
new file mode 100644
index 000000000000..c15a9910549f
--- /dev/null
+++ b/drivers/spi/spi-mtk-nor.c
@@ -0,0 +1,689 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Mediatek SPI NOR controller driver
+//
+// Copyright (C) 2020 Chuanhong Guo <gch981213@gmail.com>
+
+#include <linux/bits.h>
+#include <linux/clk.h>
+#include <linux/completion.h>
+#include <linux/dma-mapping.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+#include <linux/spi/spi-mem.h>
+#include <linux/string.h>
+
+#define DRIVER_NAME "mtk-spi-nor"
+
+#define MTK_NOR_REG_CMD			0x00
+#define MTK_NOR_CMD_WRITE		BIT(4)
+#define MTK_NOR_CMD_PROGRAM		BIT(2)
+#define MTK_NOR_CMD_READ		BIT(0)
+#define MTK_NOR_CMD_MASK		GENMASK(5, 0)
+
+#define MTK_NOR_REG_PRG_CNT		0x04
+#define MTK_NOR_REG_RDATA		0x0c
+
+#define MTK_NOR_REG_RADR0		0x10
+#define MTK_NOR_REG_RADR(n)		(MTK_NOR_REG_RADR0 + 4 * (n))
+#define MTK_NOR_REG_RADR3		0xc8
+
+#define MTK_NOR_REG_WDATA		0x1c
+
+#define MTK_NOR_REG_PRGDATA0		0x20
+#define MTK_NOR_REG_PRGDATA(n)		(MTK_NOR_REG_PRGDATA0 + 4 * (n))
+#define MTK_NOR_REG_PRGDATA_MAX		5
+
+#define MTK_NOR_REG_SHIFT0		0x38
+#define MTK_NOR_REG_SHIFT(n)		(MTK_NOR_REG_SHIFT0 + 4 * (n))
+#define MTK_NOR_REG_SHIFT_MAX		9
+
+#define MTK_NOR_REG_CFG1		0x60
+#define MTK_NOR_FAST_READ		BIT(0)
+
+#define MTK_NOR_REG_CFG2		0x64
+#define MTK_NOR_WR_CUSTOM_OP_EN		BIT(4)
+#define MTK_NOR_WR_BUF_EN		BIT(0)
+
+#define MTK_NOR_REG_PP_DATA		0x98
+
+#define MTK_NOR_REG_IRQ_STAT		0xa8
+#define MTK_NOR_REG_IRQ_EN		0xac
+#define MTK_NOR_IRQ_DMA			BIT(7)
+#define MTK_NOR_IRQ_MASK		GENMASK(7, 0)
+
+#define MTK_NOR_REG_CFG3		0xb4
+#define MTK_NOR_DISABLE_WREN		BIT(7)
+#define MTK_NOR_DISABLE_SR_POLL		BIT(5)
+
+#define MTK_NOR_REG_WP			0xc4
+#define MTK_NOR_ENABLE_SF_CMD		0x30
+
+#define MTK_NOR_REG_BUSCFG		0xcc
+#define MTK_NOR_4B_ADDR			BIT(4)
+#define MTK_NOR_QUAD_ADDR		BIT(3)
+#define MTK_NOR_QUAD_READ		BIT(2)
+#define MTK_NOR_DUAL_ADDR		BIT(1)
+#define MTK_NOR_DUAL_READ		BIT(0)
+#define MTK_NOR_BUS_MODE_MASK		GENMASK(4, 0)
+
+#define MTK_NOR_REG_DMA_CTL		0x718
+#define MTK_NOR_DMA_START		BIT(0)
+
+#define MTK_NOR_REG_DMA_FADR		0x71c
+#define MTK_NOR_REG_DMA_DADR		0x720
+#define MTK_NOR_REG_DMA_END_DADR	0x724
+
+#define MTK_NOR_PRG_MAX_SIZE		6
+// Reading DMA src/dst addresses have to be 16-byte aligned
+#define MTK_NOR_DMA_ALIGN		16
+#define MTK_NOR_DMA_ALIGN_MASK		(MTK_NOR_DMA_ALIGN - 1)
+// and we allocate a bounce buffer if destination address isn't aligned.
+#define MTK_NOR_BOUNCE_BUF_SIZE		PAGE_SIZE
+
+// Buffered page program can do one 128-byte transfer
+#define MTK_NOR_PP_SIZE			128
+
+#define CLK_TO_US(sp, clkcnt)		((clkcnt) * 1000000 / sp->spi_freq)
+
+struct mtk_nor {
+	struct spi_controller *ctlr;
+	struct device *dev;
+	void __iomem *base;
+	u8 *buffer;
+	struct clk *spi_clk;
+	struct clk *ctlr_clk;
+	unsigned int spi_freq;
+	bool wbuf_en;
+	bool has_irq;
+	struct completion op_done;
+};
+
+static inline void mtk_nor_rmw(struct mtk_nor *sp, u32 reg, u32 set, u32 clr)
+{
+	u32 val = readl(sp->base + reg);
+
+	val &= ~clr;
+	val |= set;
+	writel(val, sp->base + reg);
+}
+
+static inline int mtk_nor_cmd_exec(struct mtk_nor *sp, u32 cmd, ulong clk)
+{
+	ulong delay = CLK_TO_US(sp, clk);
+	u32 reg;
+	int ret;
+
+	writel(cmd, sp->base + MTK_NOR_REG_CMD);
+	ret = readl_poll_timeout(sp->base + MTK_NOR_REG_CMD, reg, !(reg & cmd),
+				 delay / 3, (delay + 1) * 200);
+	if (ret < 0)
+		dev_err(sp->dev, "command %u timeout.\n", cmd);
+	return ret;
+}
+
+static void mtk_nor_set_addr(struct mtk_nor *sp, const struct spi_mem_op *op)
+{
+	u32 addr = op->addr.val;
+	int i;
+
+	for (i = 0; i < 3; i++) {
+		writeb(addr & 0xff, sp->base + MTK_NOR_REG_RADR(i));
+		addr >>= 8;
+	}
+	if (op->addr.nbytes == 4) {
+		writeb(addr & 0xff, sp->base + MTK_NOR_REG_RADR3);
+		mtk_nor_rmw(sp, MTK_NOR_REG_BUSCFG, MTK_NOR_4B_ADDR, 0);
+	} else {
+		mtk_nor_rmw(sp, MTK_NOR_REG_BUSCFG, 0, MTK_NOR_4B_ADDR);
+	}
+}
+
+static bool mtk_nor_match_read(const struct spi_mem_op *op)
+{
+	int dummy = 0;
+
+	if (op->dummy.buswidth)
+		dummy = op->dummy.nbytes * BITS_PER_BYTE / op->dummy.buswidth;
+
+	if ((op->data.buswidth == 2) || (op->data.buswidth == 4)) {
+		if (op->addr.buswidth == 1)
+			return dummy == 8;
+		else if (op->addr.buswidth == 2)
+			return dummy == 4;
+		else if (op->addr.buswidth == 4)
+			return dummy == 6;
+	} else if ((op->addr.buswidth == 1) && (op->data.buswidth == 1)) {
+		if (op->cmd.opcode == 0x03)
+			return dummy == 0;
+		else if (op->cmd.opcode == 0x0b)
+			return dummy == 8;
+	}
+	return false;
+}
+
+static int mtk_nor_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
+{
+	size_t len;
+
+	if (!op->data.nbytes)
+		return 0;
+
+	if ((op->addr.nbytes == 3) || (op->addr.nbytes == 4)) {
+		if ((op->data.dir == SPI_MEM_DATA_IN) &&
+		    mtk_nor_match_read(op)) {
+			if ((op->addr.val & MTK_NOR_DMA_ALIGN_MASK) ||
+			    (op->data.nbytes < MTK_NOR_DMA_ALIGN))
+				op->data.nbytes = 1;
+			else if (!((ulong)(op->data.buf.in) &
+				   MTK_NOR_DMA_ALIGN_MASK))
+				op->data.nbytes &= ~MTK_NOR_DMA_ALIGN_MASK;
+			else if (op->data.nbytes > MTK_NOR_BOUNCE_BUF_SIZE)
+				op->data.nbytes = MTK_NOR_BOUNCE_BUF_SIZE;
+			return 0;
+		} else if (op->data.dir == SPI_MEM_DATA_OUT) {
+			if (op->data.nbytes >= MTK_NOR_PP_SIZE)
+				op->data.nbytes = MTK_NOR_PP_SIZE;
+			else
+				op->data.nbytes = 1;
+			return 0;
+		}
+	}
+
+	len = MTK_NOR_PRG_MAX_SIZE - sizeof(op->cmd.opcode) - op->addr.nbytes -
+	      op->dummy.nbytes;
+	if (op->data.nbytes > len)
+		op->data.nbytes = len;
+
+	return 0;
+}
+
+static bool mtk_nor_supports_op(struct spi_mem *mem,
+				const struct spi_mem_op *op)
+{
+	size_t len;
+
+	if (op->cmd.buswidth != 1)
+		return false;
+
+	if ((op->addr.nbytes == 3) || (op->addr.nbytes == 4)) {
+		if ((op->data.dir == SPI_MEM_DATA_IN) && mtk_nor_match_read(op))
+			return true;
+		else if (op->data.dir == SPI_MEM_DATA_OUT)
+			return (op->addr.buswidth == 1) &&
+			       (op->dummy.buswidth == 0) &&
+			       (op->data.buswidth == 1);
+	}
+	len = sizeof(op->cmd.opcode) + op->addr.nbytes + op->dummy.nbytes;
+	if ((len > MTK_NOR_PRG_MAX_SIZE) ||
+	    ((op->data.nbytes) && (len == MTK_NOR_PRG_MAX_SIZE)))
+		return false;
+	return true;
+}
+
+static void mtk_nor_setup_bus(struct mtk_nor *sp, const struct spi_mem_op *op)
+{
+	u32 reg = 0;
+
+	if (op->addr.nbytes == 4)
+		reg |= MTK_NOR_4B_ADDR;
+
+	if (op->data.buswidth == 4) {
+		reg |= MTK_NOR_QUAD_READ;
+		writeb(op->cmd.opcode, sp->base + MTK_NOR_REG_PRGDATA(4));
+		if (op->addr.buswidth == 4)
+			reg |= MTK_NOR_QUAD_ADDR;
+	} else if (op->data.buswidth == 2) {
+		reg |= MTK_NOR_DUAL_READ;
+		writeb(op->cmd.opcode, sp->base + MTK_NOR_REG_PRGDATA(3));
+		if (op->addr.buswidth == 2)
+			reg |= MTK_NOR_DUAL_ADDR;
+	} else {
+		if (op->cmd.opcode == 0x0b)
+			mtk_nor_rmw(sp, MTK_NOR_REG_CFG1, MTK_NOR_FAST_READ, 0);
+		else
+			mtk_nor_rmw(sp, MTK_NOR_REG_CFG1, 0, MTK_NOR_FAST_READ);
+	}
+	mtk_nor_rmw(sp, MTK_NOR_REG_BUSCFG, reg, MTK_NOR_BUS_MODE_MASK);
+}
+
+static int mtk_nor_read_dma(struct mtk_nor *sp, u32 from, unsigned int length,
+			    u8 *buffer)
+{
+	int ret = 0;
+	ulong delay;
+	u32 reg;
+	dma_addr_t dma_addr;
+
+	dma_addr = dma_map_single(sp->dev, buffer, length, DMA_FROM_DEVICE);
+	if (dma_mapping_error(sp->dev, dma_addr)) {
+		dev_err(sp->dev, "failed to map dma buffer.\n");
+		return -EINVAL;
+	}
+
+	writel(from, sp->base + MTK_NOR_REG_DMA_FADR);
+	writel(dma_addr, sp->base + MTK_NOR_REG_DMA_DADR);
+	writel(dma_addr + length, sp->base + MTK_NOR_REG_DMA_END_DADR);
+
+	if (sp->has_irq) {
+		reinit_completion(&sp->op_done);
+		mtk_nor_rmw(sp, MTK_NOR_REG_IRQ_EN, MTK_NOR_IRQ_DMA, 0);
+	}
+
+	mtk_nor_rmw(sp, MTK_NOR_REG_DMA_CTL, MTK_NOR_DMA_START, 0);
+
+	delay = CLK_TO_US(sp, (length + 5) * BITS_PER_BYTE);
+
+	if (sp->has_irq) {
+		if (!wait_for_completion_timeout(&sp->op_done,
+						 (delay + 1) * 100))
+			ret = -ETIMEDOUT;
+	} else {
+		ret = readl_poll_timeout(sp->base + MTK_NOR_REG_DMA_CTL, reg,
+					 !(reg & MTK_NOR_DMA_START), delay / 3,
+					 (delay + 1) * 100);
+	}
+
+	dma_unmap_single(sp->dev, dma_addr, length, DMA_FROM_DEVICE);
+	if (ret < 0)
+		dev_err(sp->dev, "dma read timeout.\n");
+
+	return ret;
+}
+
+static int mtk_nor_read_bounce(struct mtk_nor *sp, u32 from,
+			       unsigned int length, u8 *buffer)
+{
+	unsigned int rdlen;
+	int ret;
+
+	if (length & MTK_NOR_DMA_ALIGN_MASK)
+		rdlen = (length + MTK_NOR_DMA_ALIGN) & ~MTK_NOR_DMA_ALIGN_MASK;
+	else
+		rdlen = length;
+
+	ret = mtk_nor_read_dma(sp, from, rdlen, sp->buffer);
+	if (ret)
+		return ret;
+
+	memcpy(buffer, sp->buffer, length);
+	return 0;
+}
+
+static int mtk_nor_read_pio(struct mtk_nor *sp, const struct spi_mem_op *op)
+{
+	u8 *buf = op->data.buf.in;
+	int ret;
+
+	ret = mtk_nor_cmd_exec(sp, MTK_NOR_CMD_READ, 6 * BITS_PER_BYTE);
+	if (!ret)
+		buf[0] = readb(sp->base + MTK_NOR_REG_RDATA);
+	return ret;
+}
+
+static int mtk_nor_write_buffer_enable(struct mtk_nor *sp)
+{
+	int ret;
+	u32 val;
+
+	if (sp->wbuf_en)
+		return 0;
+
+	val = readl(sp->base + MTK_NOR_REG_CFG2);
+	writel(val | MTK_NOR_WR_BUF_EN, sp->base + MTK_NOR_REG_CFG2);
+	ret = readl_poll_timeout(sp->base + MTK_NOR_REG_CFG2, val,
+				 val & MTK_NOR_WR_BUF_EN, 0, 10000);
+	if (!ret)
+		sp->wbuf_en = true;
+	return ret;
+}
+
+static int mtk_nor_write_buffer_disable(struct mtk_nor *sp)
+{
+	int ret;
+	u32 val;
+
+	if (!sp->wbuf_en)
+		return 0;
+	val = readl(sp->base + MTK_NOR_REG_CFG2);
+	writel(val & ~MTK_NOR_WR_BUF_EN, sp->base + MTK_NOR_REG_CFG2);
+	ret = readl_poll_timeout(sp->base + MTK_NOR_REG_CFG2, val,
+				 !(val & MTK_NOR_WR_BUF_EN), 0, 10000);
+	if (!ret)
+		sp->wbuf_en = false;
+	return ret;
+}
+
+static int mtk_nor_pp_buffered(struct mtk_nor *sp, const struct spi_mem_op *op)
+{
+	const u8 *buf = op->data.buf.out;
+	u32 val;
+	int ret, i;
+
+	ret = mtk_nor_write_buffer_enable(sp);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0; i < op->data.nbytes; i += 4) {
+		val = buf[i + 3] << 24 | buf[i + 2] << 16 | buf[i + 1] << 8 |
+		      buf[i];
+		writel(val, sp->base + MTK_NOR_REG_PP_DATA);
+	}
+	return mtk_nor_cmd_exec(sp, MTK_NOR_CMD_WRITE,
+				(op->data.nbytes + 5) * BITS_PER_BYTE);
+}
+
+static int mtk_nor_pp_unbuffered(struct mtk_nor *sp,
+				 const struct spi_mem_op *op)
+{
+	const u8 *buf = op->data.buf.out;
+	int ret;
+
+	ret = mtk_nor_write_buffer_disable(sp);
+	if (ret < 0)
+		return ret;
+	writeb(buf[0], sp->base + MTK_NOR_REG_WDATA);
+	return mtk_nor_cmd_exec(sp, MTK_NOR_CMD_WRITE, 6 * BITS_PER_BYTE);
+}
+
+int mtk_nor_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
+{
+	struct mtk_nor *sp = spi_controller_get_devdata(mem->spi->master);
+	int ret;
+
+	if ((op->data.nbytes == 0) ||
+	    ((op->addr.nbytes != 3) && (op->addr.nbytes != 4)))
+		return -ENOTSUPP;
+
+	if (op->data.dir == SPI_MEM_DATA_OUT) {
+		mtk_nor_set_addr(sp, op);
+		writeb(op->cmd.opcode, sp->base + MTK_NOR_REG_PRGDATA0);
+		if (op->data.nbytes == MTK_NOR_PP_SIZE)
+			return mtk_nor_pp_buffered(sp, op);
+		return mtk_nor_pp_unbuffered(sp, op);
+	}
+
+	if ((op->data.dir == SPI_MEM_DATA_IN) && mtk_nor_match_read(op)) {
+		ret = mtk_nor_write_buffer_disable(sp);
+		if (ret < 0)
+			return ret;
+		mtk_nor_setup_bus(sp, op);
+		if (op->data.nbytes == 1) {
+			mtk_nor_set_addr(sp, op);
+			return mtk_nor_read_pio(sp, op);
+		} else if (((ulong)(op->data.buf.in) &
+			    MTK_NOR_DMA_ALIGN_MASK)) {
+			return mtk_nor_read_bounce(sp, op->addr.val,
+						   op->data.nbytes,
+						   op->data.buf.in);
+		} else {
+			return mtk_nor_read_dma(sp, op->addr.val,
+						op->data.nbytes,
+						op->data.buf.in);
+		}
+	}
+
+	return -ENOTSUPP;
+}
+
+static int mtk_nor_setup(struct spi_device *spi)
+{
+	struct mtk_nor *sp = spi_controller_get_devdata(spi->master);
+
+	if (spi->max_speed_hz && (spi->max_speed_hz < sp->spi_freq)) {
+		dev_err(&spi->dev, "spi clock should be %u Hz.\n",
+			sp->spi_freq);
+		return -EINVAL;
+	}
+	spi->max_speed_hz = sp->spi_freq;
+
+	return 0;
+}
+
+static int mtk_nor_transfer_one_message(struct spi_controller *master,
+					struct spi_message *m)
+{
+	struct mtk_nor *sp = spi_controller_get_devdata(master);
+	struct spi_transfer *t = NULL;
+	unsigned long trx_len = 0;
+	int stat = 0;
+	int reg_offset = MTK_NOR_REG_PRGDATA_MAX;
+	void __iomem *reg;
+	const u8 *txbuf;
+	u8 *rxbuf;
+	int i;
+
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		txbuf = t->tx_buf;
+		for (i = 0; i < t->len; i++, reg_offset--) {
+			reg = sp->base + MTK_NOR_REG_PRGDATA(reg_offset);
+			if (txbuf)
+				writeb(txbuf[i], reg);
+			else
+				writeb(0, reg);
+		}
+		trx_len += t->len;
+	}
+
+	writel(trx_len * BITS_PER_BYTE, sp->base + MTK_NOR_REG_PRG_CNT);
+
+	stat = mtk_nor_cmd_exec(sp, MTK_NOR_CMD_PROGRAM,
+				trx_len * BITS_PER_BYTE);
+	if (stat < 0)
+		goto msg_done;
+
+	reg_offset = trx_len - 1;
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		rxbuf = t->rx_buf;
+		for (i = 0; i < t->len; i++, reg_offset--) {
+			reg = sp->base + MTK_NOR_REG_SHIFT(reg_offset);
+			if (rxbuf)
+				rxbuf[i] = readb(reg);
+		}
+	}
+
+	m->actual_length = trx_len;
+msg_done:
+	m->status = stat;
+	spi_finalize_current_message(master);
+
+	return 0;
+}
+
+static void mtk_nor_disable_clk(struct mtk_nor *sp)
+{
+	clk_disable_unprepare(sp->spi_clk);
+	clk_disable_unprepare(sp->ctlr_clk);
+}
+
+static int mtk_nor_enable_clk(struct mtk_nor *sp)
+{
+	int ret;
+
+	ret = clk_prepare_enable(sp->spi_clk);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare_enable(sp->ctlr_clk);
+	if (ret) {
+		clk_disable_unprepare(sp->spi_clk);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int mtk_nor_init(struct mtk_nor *sp)
+{
+	int ret;
+
+	ret = mtk_nor_enable_clk(sp);
+	if (ret)
+		return ret;
+
+	sp->spi_freq = clk_get_rate(sp->spi_clk);
+
+	writel(MTK_NOR_ENABLE_SF_CMD, sp->base + MTK_NOR_REG_WP);
+	mtk_nor_rmw(sp, MTK_NOR_REG_CFG2, MTK_NOR_WR_CUSTOM_OP_EN, 0);
+	mtk_nor_rmw(sp, MTK_NOR_REG_CFG3,
+		    MTK_NOR_DISABLE_WREN | MTK_NOR_DISABLE_SR_POLL, 0);
+
+	return ret;
+}
+
+static irqreturn_t mtk_nor_irq_handler(int irq, void *data)
+{
+	struct mtk_nor *sp = data;
+	u32 irq_status, irq_enabled;
+
+	irq_status = readl(sp->base + MTK_NOR_REG_IRQ_STAT);
+	irq_enabled = readl(sp->base + MTK_NOR_REG_IRQ_EN);
+	// write status back to clear interrupt
+	writel(irq_status, sp->base + MTK_NOR_REG_IRQ_STAT);
+
+	if (!(irq_status & irq_enabled))
+		return IRQ_NONE;
+
+	if (irq_status & MTK_NOR_IRQ_DMA) {
+		complete(&sp->op_done);
+		writel(0, sp->base + MTK_NOR_REG_IRQ_EN);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static size_t mtk_max_msg_size(struct spi_device *spi)
+{
+	return MTK_NOR_PRG_MAX_SIZE;
+}
+
+static const struct spi_controller_mem_ops mtk_nor_mem_ops = {
+	.adjust_op_size = mtk_nor_adjust_op_size,
+	.supports_op = mtk_nor_supports_op,
+	.exec_op = mtk_nor_exec_op
+};
+
+static const struct of_device_id mtk_nor_match[] = {
+	{ .compatible = "mediatek,mt8173-nor" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mtk_nor_match);
+
+static int mtk_nor_probe(struct platform_device *pdev)
+{
+	struct spi_controller *ctlr;
+	struct mtk_nor *sp;
+	void __iomem *base;
+	u8 *buffer;
+	struct clk *spi_clk, *ctlr_clk;
+	int ret, irq;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	spi_clk = devm_clk_get(&pdev->dev, "spi");
+	if (IS_ERR(spi_clk))
+		return PTR_ERR(spi_clk);
+
+	ctlr_clk = devm_clk_get(&pdev->dev, "sf");
+	if (IS_ERR(ctlr_clk))
+		return PTR_ERR(ctlr_clk);
+
+	buffer = devm_kmalloc(&pdev->dev,
+			      MTK_NOR_BOUNCE_BUF_SIZE + MTK_NOR_DMA_ALIGN,
+			      GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	if ((ulong)buffer & MTK_NOR_DMA_ALIGN_MASK)
+		buffer = (u8 *)(((ulong)buffer + MTK_NOR_DMA_ALIGN) &
+				~MTK_NOR_DMA_ALIGN_MASK);
+
+	ctlr = spi_alloc_master(&pdev->dev, sizeof(*sp));
+	if (!ctlr) {
+		dev_err(&pdev->dev, "failed to allocate spi controller\n");
+		return -ENOMEM;
+	}
+
+	ctlr->bits_per_word_mask = SPI_BPW_MASK(8);
+	ctlr->dev.of_node = pdev->dev.of_node;
+	ctlr->max_message_size = mtk_max_msg_size;
+	ctlr->mem_ops = &mtk_nor_mem_ops;
+	ctlr->mode_bits = SPI_RX_DUAL | SPI_RX_QUAD | SPI_TX_DUAL | SPI_TX_QUAD;
+	ctlr->num_chipselect = 1;
+	ctlr->setup = mtk_nor_setup;
+	ctlr->transfer_one_message = mtk_nor_transfer_one_message;
+
+	dev_set_drvdata(&pdev->dev, ctlr);
+
+	sp = spi_controller_get_devdata(ctlr);
+	sp->base = base;
+	sp->buffer = buffer;
+	sp->has_irq = false;
+	sp->wbuf_en = false;
+	sp->ctlr = ctlr;
+	sp->dev = &pdev->dev;
+	sp->spi_clk = spi_clk;
+	sp->ctlr_clk = ctlr_clk;
+
+	irq = platform_get_irq_optional(pdev, 0);
+	if (irq < 0) {
+		dev_warn(sp->dev, "IRQ not available.");
+	} else {
+		writel(MTK_NOR_IRQ_MASK, base + MTK_NOR_REG_IRQ_STAT);
+		writel(0, base + MTK_NOR_REG_IRQ_EN);
+		ret = devm_request_irq(sp->dev, irq, mtk_nor_irq_handler, 0,
+				       pdev->name, sp);
+		if (ret < 0) {
+			dev_warn(sp->dev, "failed to request IRQ.");
+		} else {
+			init_completion(&sp->op_done);
+			sp->has_irq = true;
+		}
+	}
+
+	ret = mtk_nor_init(sp);
+	if (ret < 0) {
+		kfree(ctlr);
+		return ret;
+	}
+
+	dev_info(&pdev->dev, "spi frequency: %d Hz\n", sp->spi_freq);
+
+	return devm_spi_register_controller(&pdev->dev, ctlr);
+}
+
+static int mtk_nor_remove(struct platform_device *pdev)
+{
+	struct spi_controller *ctlr;
+	struct mtk_nor *sp;
+
+	ctlr = dev_get_drvdata(&pdev->dev);
+	sp = spi_controller_get_devdata(ctlr);
+
+	mtk_nor_disable_clk(sp);
+
+	return 0;
+}
+
+static struct platform_driver mtk_nor_driver = {
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = mtk_nor_match,
+	},
+	.probe = mtk_nor_probe,
+	.remove = mtk_nor_remove,
+};
+
+module_platform_driver(mtk_nor_driver);
+
+MODULE_DESCRIPTION("Mediatek SPI NOR controller driver");
+MODULE_AUTHOR("Chuanhong Guo <gch981213@gmail.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRIVER_NAME);
-- 
2.24.1