patches/1276-spi-Extend-the-core-to-ease-integration-of-SPI-memor.patch

From 659020c82ecd59d7bd7a34f2ce1fb32e5e5180b2 Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon@bootlin.com>
Date: Thu, 26 Apr 2018 18:18:14 +0200
Subject: [PATCH 1276/1795] spi: Extend the core to ease integration of SPI
 memory controllers

Some controllers are exposing high-level interfaces to access various
kind of SPI memories. Unfortunately they do not fit in the current
spi_controller model and usually have drivers placed in
drivers/mtd/spi-nor which are only supporting SPI NORs and not SPI
memories in general.

This is an attempt at defining a SPI memory interface which works for
all kinds of SPI memories (NORs, NANDs, SRAMs).

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Frieder Schrempf <frieder.schrempf@exceet.de>
Tested-by: Frieder Schrempf <frieder.schrempf@exceet.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
(cherry picked from commit c36ff266dc82f4ae797a6f3513c6ffa344f7f1c7)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/spi/Kconfig         |   7 +
 drivers/spi/Makefile        |   1 +
 drivers/spi/spi-mem.c       | 410 ++++++++++++++++++++++++++++++++++++
 include/linux/spi/spi-mem.h | 249 ++++++++++++++++++++++
 include/linux/spi/spi.h     |   7 +
 5 files changed, 674 insertions(+)
 create mode 100644 drivers/spi/spi-mem.c
 create mode 100644 include/linux/spi/spi-mem.h

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index a75f2a2cf780..378e6a40b6a4 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -51,6 +51,13 @@ config SPI_MASTER
 
 if SPI_MASTER
 
+config SPI_MEM
+	bool "SPI memory extension"
+	help
+	  Enable this option if you want to enable the SPI memory extension.
+	  This extension is meant to simplify interaction with SPI memories
+	  by providing an high-level interface to send memory-like commands.
+
 comment "SPI Master Controller Drivers"
 
 config SPI_ALTERA
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 8e0cda73b324..d95bfe95d295 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -8,6 +8,7 @@ ccflags-$(CONFIG_SPI_DEBUG) := -DDEBUG
 # small core, mostly translating board-specific
 # config declarations into driver model code
 obj-$(CONFIG_SPI_MASTER)		+= spi.o
+obj-$(CONFIG_SPI_MEM)			+= spi-mem.o
 obj-$(CONFIG_SPI_SPIDEV)		+= spidev.o
 obj-$(CONFIG_SPI_LOOPBACK_TEST)		+= spi-loopback-test.o
 
diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
new file mode 100644
index 000000000000..990770dfa5cf
--- /dev/null
+++ b/drivers/spi/spi-mem.c
@@ -0,0 +1,410 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Exceet Electronics GmbH
+ * Copyright (C) 2018 Bootlin
+ *
+ * Author: Boris Brezillon <boris.brezillon@bootlin.com>
+ */
+#include <linux/dmaengine.h>
+#include <linux/pm_runtime.h>
+#include <linux/spi/spi.h>
+#include <linux/spi/spi-mem.h>
+
+#include "internals.h"
+
+/**
+ * spi_controller_dma_map_mem_op_data() - DMA-map the buffer attached to a
+ *					  memory operation
+ * @ctlr: the SPI controller requesting this dma_map()
+ * @op: the memory operation containing the buffer to map
+ * @sgt: a pointer to a non-initialized sg_table that will be filled by this
+ *	 function
+ *
+ * Some controllers might want to do DMA on the data buffer embedded in @op.
+ * This helper prepares everything for you and provides a ready-to-use
+ * sg_table. This function is not intended to be called from spi drivers.
+ * Only SPI controller drivers should use it.
+ * Note that the caller must ensure the memory region pointed by
+ * op->data.buf.{in,out} is DMA-able before calling this function.
+ *
+ * Return: 0 in case of success, a negative error code otherwise.
+ */
+int spi_controller_dma_map_mem_op_data(struct spi_controller *ctlr,
+				       const struct spi_mem_op *op,
+				       struct sg_table *sgt)
+{
+	struct device *dmadev;
+
+	if (!op->data.nbytes)
+		return -EINVAL;
+
+	if (op->data.dir == SPI_MEM_DATA_OUT && ctlr->dma_tx)
+		dmadev = ctlr->dma_tx->device->dev;
+	else if (op->data.dir == SPI_MEM_DATA_IN && ctlr->dma_rx)
+		dmadev = ctlr->dma_rx->device->dev;
+	else
+		dmadev = ctlr->dev.parent;
+
+	if (!dmadev)
+		return -EINVAL;
+
+	return spi_map_buf(ctlr, dmadev, sgt, op->data.buf.in, op->data.nbytes,
+			   op->data.dir == SPI_MEM_DATA_IN ?
+			   DMA_FROM_DEVICE : DMA_TO_DEVICE);
+}
+EXPORT_SYMBOL_GPL(spi_controller_dma_map_mem_op_data);
+
+/**
+ * spi_controller_dma_unmap_mem_op_data() - DMA-unmap the buffer attached to a
+ *					    memory operation
+ * @ctlr: the SPI controller requesting this dma_unmap()
+ * @op: the memory operation containing the buffer to unmap
+ * @sgt: a pointer to an sg_table previously initialized by
+ *	 spi_controller_dma_map_mem_op_data()
+ *
+ * Some controllers might want to do DMA on the data buffer embedded in @op.
+ * This helper prepares things so that the CPU can access the
+ * op->data.buf.{in,out} buffer again.
+ *
+ * This function is not intended to be called from SPI drivers. Only SPI
+ * controller drivers should use it.
+ *
+ * This function should be called after the DMA operation has finished and is
+ * only valid if the previous spi_controller_dma_map_mem_op_data() call
+ * returned 0.
+ *
+ * Return: 0 in case of success, a negative error code otherwise.
+ */
+void spi_controller_dma_unmap_mem_op_data(struct spi_controller *ctlr,
+					  const struct spi_mem_op *op,
+					  struct sg_table *sgt)
+{
+	struct device *dmadev;
+
+	if (!op->data.nbytes)
+		return;
+
+	if (op->data.dir == SPI_MEM_DATA_OUT && ctlr->dma_tx)
+		dmadev = ctlr->dma_tx->device->dev;
+	else if (op->data.dir == SPI_MEM_DATA_IN && ctlr->dma_rx)
+		dmadev = ctlr->dma_rx->device->dev;
+	else
+		dmadev = ctlr->dev.parent;
+
+	spi_unmap_buf(ctlr, dmadev, sgt,
+		      op->data.dir == SPI_MEM_DATA_IN ?
+		      DMA_FROM_DEVICE : DMA_TO_DEVICE);
+}
+EXPORT_SYMBOL_GPL(spi_controller_dma_unmap_mem_op_data);
+
+static int spi_check_buswidth_req(struct spi_mem *mem, u8 buswidth, bool tx)
+{
+	u32 mode = mem->spi->mode;
+
+	switch (buswidth) {
+	case 1:
+		return 0;
+
+	case 2:
+		if ((tx && (mode & (SPI_TX_DUAL | SPI_TX_QUAD))) ||
+		    (!tx && (mode & (SPI_RX_DUAL | SPI_RX_QUAD))))
+			return 0;
+
+		break;
+
+	case 4:
+		if ((tx && (mode & SPI_TX_QUAD)) ||
+		    (!tx && (mode & SPI_RX_QUAD)))
+			return 0;
+
+		break;
+
+	default:
+		break;
+	}
+
+	return -ENOTSUPP;
+}
+
+static bool spi_mem_default_supports_op(struct spi_mem *mem,
+					const struct spi_mem_op *op)
+{
+	if (spi_check_buswidth_req(mem, op->cmd.buswidth, true))
+		return false;
+
+	if (op->addr.nbytes &&
+	    spi_check_buswidth_req(mem, op->addr.buswidth, true))
+		return false;
+
+	if (op->dummy.nbytes &&
+	    spi_check_buswidth_req(mem, op->dummy.buswidth, true))
+		return false;
+
+	if (op->data.nbytes &&
+	    spi_check_buswidth_req(mem, op->data.buswidth,
+				   op->data.dir == SPI_MEM_DATA_OUT))
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(spi_mem_default_supports_op);
+
+/**
+ * spi_mem_supports_op() - Check if a memory device and the controller it is
+ *			   connected to support a specific memory operation
+ * @mem: the SPI memory
+ * @op: the memory operation to check
+ *
+ * Some controllers are only supporting Single or Dual IOs, others might only
+ * support specific opcodes, or it can even be that the controller and device
+ * both support Quad IOs but the hardware prevents you from using it because
+ * only 2 IO lines are connected.
+ *
+ * This function checks whether a specific operation is supported.
+ *
+ * Return: true if @op is supported, false otherwise.
+ */
+bool spi_mem_supports_op(struct spi_mem *mem, const struct spi_mem_op *op)
+{
+	struct spi_controller *ctlr = mem->spi->controller;
+
+	if (ctlr->mem_ops && ctlr->mem_ops->supports_op)
+		return ctlr->mem_ops->supports_op(mem, op);
+
+	return spi_mem_default_supports_op(mem, op);
+}
+EXPORT_SYMBOL_GPL(spi_mem_supports_op);
+
+/**
+ * spi_mem_exec_op() - Execute a memory operation
+ * @mem: the SPI memory
+ * @op: the memory operation to execute
+ *
+ * Executes a memory operation.
+ *
+ * This function first checks that @op is supported and then tries to execute
+ * it.
+ *
+ * Return: 0 in case of success, a negative error code otherwise.
+ */
+int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
+{
+	unsigned int tmpbufsize, xferpos = 0, totalxferlen = 0;
+	struct spi_controller *ctlr = mem->spi->controller;
+	struct spi_transfer xfers[4] = { };
+	struct spi_message msg;
+	u8 *tmpbuf;
+	int ret;
+
+	if (!spi_mem_supports_op(mem, op))
+		return -ENOTSUPP;
+
+	if (ctlr->mem_ops) {
+		/*
+		 * Flush the message queue before executing our SPI memory
+		 * operation to prevent preemption of regular SPI transfers.
+		 */
+		spi_flush_queue(ctlr);
+
+		if (ctlr->auto_runtime_pm) {
+			ret = pm_runtime_get_sync(ctlr->dev.parent);
+			if (ret < 0) {
+				dev_err(&ctlr->dev,
+					"Failed to power device: %d\n",
+					ret);
+				return ret;
+			}
+		}
+
+		mutex_lock(&ctlr->bus_lock_mutex);
+		mutex_lock(&ctlr->io_mutex);
+		ret = ctlr->mem_ops->exec_op(mem, op);
+		mutex_unlock(&ctlr->io_mutex);
+		mutex_unlock(&ctlr->bus_lock_mutex);
+
+		if (ctlr->auto_runtime_pm)
+			pm_runtime_put(ctlr->dev.parent);
+
+		/*
+		 * Some controllers only optimize specific paths (typically the
+		 * read path) and expect the core to use the regular SPI
+		 * interface in other cases.
+		 */
+		if (!ret || ret != -ENOTSUPP)
+			return ret;
+	}
+
+	tmpbufsize = sizeof(op->cmd.opcode) + op->addr.nbytes +
+		     op->dummy.nbytes;
+
+	/*
+	 * Allocate a buffer to transmit the CMD, ADDR cycles with kmalloc() so
+	 * we're guaranteed that this buffer is DMA-able, as required by the
+	 * SPI layer.
+	 */
+	tmpbuf = kzalloc(tmpbufsize, GFP_KERNEL | GFP_DMA);
+	if (!tmpbuf)
+		return -ENOMEM;
+
+	spi_message_init(&msg);
+
+	tmpbuf[0] = op->cmd.opcode;
+	xfers[xferpos].tx_buf = tmpbuf;
+	xfers[xferpos].len = sizeof(op->cmd.opcode);
+	xfers[xferpos].tx_nbits = op->cmd.buswidth;
+	spi_message_add_tail(&xfers[xferpos], &msg);
+	xferpos++;
+	totalxferlen++;
+
+	if (op->addr.nbytes) {
+		int i;
+
+		for (i = 0; i < op->addr.nbytes; i++)
+			tmpbuf[i + 1] = op->addr.val >>
+					(8 * (op->addr.nbytes - i - 1));
+
+		xfers[xferpos].tx_buf = tmpbuf + 1;
+		xfers[xferpos].len = op->addr.nbytes;
+		xfers[xferpos].tx_nbits = op->addr.buswidth;
+		spi_message_add_tail(&xfers[xferpos], &msg);
+		xferpos++;
+		totalxferlen += op->addr.nbytes;
+	}
+
+	if (op->dummy.nbytes) {
+		memset(tmpbuf + op->addr.nbytes + 1, 0xff, op->dummy.nbytes);
+		xfers[xferpos].tx_buf = tmpbuf + op->addr.nbytes + 1;
+		xfers[xferpos].len = op->dummy.nbytes;
+		xfers[xferpos].tx_nbits = op->dummy.buswidth;
+		spi_message_add_tail(&xfers[xferpos], &msg);
+		xferpos++;
+		totalxferlen += op->dummy.nbytes;
+	}
+
+	if (op->data.nbytes) {
+		if (op->data.dir == SPI_MEM_DATA_IN) {
+			xfers[xferpos].rx_buf = op->data.buf.in;
+			xfers[xferpos].rx_nbits = op->data.buswidth;
+		} else {
+			xfers[xferpos].tx_buf = op->data.buf.out;
+			xfers[xferpos].tx_nbits = op->data.buswidth;
+		}
+
+		xfers[xferpos].len = op->data.nbytes;
+		spi_message_add_tail(&xfers[xferpos], &msg);
+		xferpos++;
+		totalxferlen += op->data.nbytes;
+	}
+
+	ret = spi_sync(mem->spi, &msg);
+
+	kfree(tmpbuf);
+
+	if (ret)
+		return ret;
+
+	if (msg.actual_length != totalxferlen)
+		return -EIO;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_mem_exec_op);
+
+/**
+ * spi_mem_adjust_op_size() - Adjust the data size of a SPI mem operation to
+ *			      match controller limitations
+ * @mem: the SPI memory
+ * @op: the operation to adjust
+ *
+ * Some controllers have FIFO limitations and must split a data transfer
+ * operation into multiple ones, others require a specific alignment for
+ * optimized accesses. This function allows SPI mem drivers to split a single
+ * operation into multiple sub-operations when required.
+ *
+ * Return: a negative error code if the controller can't properly adjust @op,
+ *	   0 otherwise. Note that @op->data.nbytes will be updated if @op
+ *	   can't be handled in a single step.
+ */
+int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
+{
+	struct spi_controller *ctlr = mem->spi->controller;
+
+	if (ctlr->mem_ops && ctlr->mem_ops->adjust_op_size)
+		return ctlr->mem_ops->adjust_op_size(mem, op);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_mem_adjust_op_size);
+
+static inline struct spi_mem_driver *to_spi_mem_drv(struct device_driver *drv)
+{
+	return container_of(drv, struct spi_mem_driver, spidrv.driver);
+}
+
+static int spi_mem_probe(struct spi_device *spi)
+{
+	struct spi_mem_driver *memdrv = to_spi_mem_drv(spi->dev.driver);
+	struct spi_mem *mem;
+
+	mem = devm_kzalloc(&spi->dev, sizeof(*mem), GFP_KERNEL);
+	if (!mem)
+		return -ENOMEM;
+
+	mem->spi = spi;
+	spi_set_drvdata(spi, mem);
+
+	return memdrv->probe(mem);
+}
+
+static int spi_mem_remove(struct spi_device *spi)
+{
+	struct spi_mem_driver *memdrv = to_spi_mem_drv(spi->dev.driver);
+	struct spi_mem *mem = spi_get_drvdata(spi);
+
+	if (memdrv->remove)
+		return memdrv->remove(mem);
+
+	return 0;
+}
+
+static void spi_mem_shutdown(struct spi_device *spi)
+{
+	struct spi_mem_driver *memdrv = to_spi_mem_drv(spi->dev.driver);
+	struct spi_mem *mem = spi_get_drvdata(spi);
+
+	if (memdrv->shutdown)
+		memdrv->shutdown(mem);
+}
+
+/**
+ * spi_mem_driver_register_with_owner() - Register a SPI memory driver
+ * @memdrv: the SPI memory driver to register
+ * @owner: the owner of this driver
+ *
+ * Registers a SPI memory driver.
+ *
+ * Return: 0 in case of success, a negative error core otherwise.
+ */
+
+int spi_mem_driver_register_with_owner(struct spi_mem_driver *memdrv,
+				       struct module *owner)
+{
+	memdrv->spidrv.probe = spi_mem_probe;
+	memdrv->spidrv.remove = spi_mem_remove;
+	memdrv->spidrv.shutdown = spi_mem_shutdown;
+
+	return __spi_register_driver(owner, &memdrv->spidrv);
+}
+EXPORT_SYMBOL_GPL(spi_mem_driver_register_with_owner);
+
+/**
+ * spi_mem_driver_unregister_with_owner() - Unregister a SPI memory driver
+ * @memdrv: the SPI memory driver to unregister
+ *
+ * Unregisters a SPI memory driver.
+ */
+void spi_mem_driver_unregister(struct spi_mem_driver *memdrv)
+{
+	spi_unregister_driver(&memdrv->spidrv);
+}
+EXPORT_SYMBOL_GPL(spi_mem_driver_unregister);
diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
new file mode 100644
index 000000000000..bb4bd15ae1f6
--- /dev/null
+++ b/include/linux/spi/spi-mem.h
@@ -0,0 +1,249 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2018 Exceet Electronics GmbH
+ * Copyright (C) 2018 Bootlin
+ *
+ * Author: Boris Brezillon <boris.brezillon@bootlin.com>
+ */
+
+#ifndef __LINUX_SPI_MEM_H
+#define __LINUX_SPI_MEM_H
+
+#include <linux/spi/spi.h>
+
+#define SPI_MEM_OP_CMD(__opcode, __buswidth)			\
+	{							\
+		.buswidth = __buswidth,				\
+		.opcode = __opcode,				\
+	}
+
+#define SPI_MEM_OP_ADDR(__nbytes, __val, __buswidth)		\
+	{							\
+		.nbytes = __nbytes,				\
+		.val = __val,					\
+		.buswidth = __buswidth,				\
+	}
+
+#define SPI_MEM_OP_NO_ADDR	{ }
+
+#define SPI_MEM_OP_DUMMY(__nbytes, __buswidth)			\
+	{							\
+		.nbytes = __nbytes,				\
+		.buswidth = __buswidth,				\
+	}
+
+#define SPI_MEM_OP_NO_DUMMY	{ }
+
+#define SPI_MEM_OP_DATA_IN(__nbytes, __buf, __buswidth)		\
+	{							\
+		.dir = SPI_MEM_DATA_IN,				\
+		.nbytes = __nbytes,				\
+		.buf.in = __buf,				\
+		.buswidth = __buswidth,				\
+	}
+
+#define SPI_MEM_OP_DATA_OUT(__nbytes, __buf, __buswidth)	\
+	{							\
+		.dir = SPI_MEM_DATA_OUT,			\
+		.nbytes = __nbytes,				\
+		.buf.out = __buf,				\
+		.buswidth = __buswidth,				\
+	}
+
+#define SPI_MEM_OP_NO_DATA	{ }
+
+/**
+ * enum spi_mem_data_dir - describes the direction of a SPI memory data
+ *			   transfer from the controller perspective
+ * @SPI_MEM_DATA_IN: data coming from the SPI memory
+ * @SPI_MEM_DATA_OUT: data sent the SPI memory
+ */
+enum spi_mem_data_dir {
+	SPI_MEM_DATA_IN,
+	SPI_MEM_DATA_OUT,
+};
+
+/**
+ * struct spi_mem_op - describes a SPI memory operation
+ * @cmd.buswidth: number of IO lines used to transmit the command
+ * @cmd.opcode: operation opcode
+ * @addr.nbytes: number of address bytes to send. Can be zero if the operation
+ *		 does not need to send an address
+ * @addr.buswidth: number of IO lines used to transmit the address cycles
+ * @addr.val: address value. This value is always sent MSB first on the bus.
+ *	      Note that only @addr.nbytes are taken into account in this
+ *	      address value, so users should make sure the value fits in the
+ *	      assigned number of bytes.
+ * @dummy.nbytes: number of dummy bytes to send after an opcode or address. Can
+ *		  be zero if the operation does not require dummy bytes
+ * @dummy.buswidth: number of IO lanes used to transmit the dummy bytes
+ * @data.buswidth: number of IO lanes used to send/receive the data
+ * @data.dir: direction of the transfer
+ * @data.buf.in: input buffer
+ * @data.buf.out: output buffer
+ */
+struct spi_mem_op {
+	struct {
+		u8 buswidth;
+		u8 opcode;
+	} cmd;
+
+	struct {
+		u8 nbytes;
+		u8 buswidth;
+		u64 val;
+	} addr;
+
+	struct {
+		u8 nbytes;
+		u8 buswidth;
+	} dummy;
+
+	struct {
+		u8 buswidth;
+		enum spi_mem_data_dir dir;
+		unsigned int nbytes;
+		/* buf.{in,out} must be DMA-able. */
+		union {
+			void *in;
+			const void *out;
+		} buf;
+	} data;
+};
+
+#define SPI_MEM_OP(__cmd, __addr, __dummy, __data)		\
+	{							\
+		.cmd = __cmd,					\
+		.addr = __addr,					\
+		.dummy = __dummy,				\
+		.data = __data,					\
+	}
+
+/**
+ * struct spi_mem - describes a SPI memory device
+ * @spi: the underlying SPI device
+ * @drvpriv: spi_mem_drviver private data
+ *
+ * Extra information that describe the SPI memory device and may be needed by
+ * the controller to properly handle this device should be placed here.
+ *
+ * One example would be the device size since some controller expose their SPI
+ * mem devices through a io-mapped region.
+ */
+struct spi_mem {
+	struct spi_device *spi;
+	void *drvpriv;
+};
+
+/**
+ * struct spi_mem_set_drvdata() - attach driver private data to a SPI mem
+ *				  device
+ * @mem: memory device
+ * @data: data to attach to the memory device
+ */
+static inline void spi_mem_set_drvdata(struct spi_mem *mem, void *data)
+{
+	mem->drvpriv = data;
+}
+
+/**
+ * struct spi_mem_get_drvdata() - get driver private data attached to a SPI mem
+ *				  device
+ * @mem: memory device
+ *
+ * Return: the data attached to the mem device.
+ */
+static inline void *spi_mem_get_drvdata(struct spi_mem *mem)
+{
+	return mem->drvpriv;
+}
+
+/**
+ * struct spi_controller_mem_ops - SPI memory operations
+ * @adjust_op_size: shrink the data xfer of an operation to match controller's
+ *		    limitations (can be alignment of max RX/TX size
+ *		    limitations)
+ * @supports_op: check if an operation is supported by the controller
+ * @exec_op: execute a SPI memory operation
+ *
+ * This interface should be implemented by SPI controllers providing an
+ * high-level interface to execute SPI memory operation, which is usually the
+ * case for QSPI controllers.
+ */
+struct spi_controller_mem_ops {
+	int (*adjust_op_size)(struct spi_mem *mem, struct spi_mem_op *op);
+	bool (*supports_op)(struct spi_mem *mem,
+			    const struct spi_mem_op *op);
+	int (*exec_op)(struct spi_mem *mem,
+		       const struct spi_mem_op *op);
+};
+
+/**
+ * struct spi_mem_driver - SPI memory driver
+ * @spidrv: inherit from a SPI driver
+ * @probe: probe a SPI memory. Usually where detection/initialization takes
+ *	   place
+ * @remove: remove a SPI memory
+ * @shutdown: take appropriate action when the system is shutdown
+ *
+ * This is just a thin wrapper around a spi_driver. The core takes care of
+ * allocating the spi_mem object and forwarding the probe/remove/shutdown
+ * request to the spi_mem_driver. The reason we use this wrapper is because
+ * we might have to stuff more information into the spi_mem struct to let
+ * SPI controllers know more about the SPI memory they interact with, and
+ * having this intermediate layer allows us to do that without adding more
+ * useless fields to the spi_device object.
+ */
+struct spi_mem_driver {
+	struct spi_driver spidrv;
+	int (*probe)(struct spi_mem *mem);
+	int (*remove)(struct spi_mem *mem);
+	void (*shutdown)(struct spi_mem *mem);
+};
+
+#if IS_ENABLED(CONFIG_SPI_MEM)
+int spi_controller_dma_map_mem_op_data(struct spi_controller *ctlr,
+				       const struct spi_mem_op *op,
+				       struct sg_table *sg);
+
+void spi_controller_dma_unmap_mem_op_data(struct spi_controller *ctlr,
+					  const struct spi_mem_op *op,
+					  struct sg_table *sg);
+#else
+static inline int
+spi_controller_dma_map_mem_op_data(struct spi_controller *ctlr,
+				   const struct spi_mem_op *op,
+				   struct sg_table *sg)
+{
+	return -ENOTSUPP;
+}
+
+static inline void
+spi_controller_dma_unmap_mem_op_data(struct spi_controller *ctlr,
+				     const struct spi_mem_op *op,
+				     struct sg_table *sg)
+{
+}
+#endif /* CONFIG_SPI_MEM */
+
+int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op);
+
+bool spi_mem_supports_op(struct spi_mem *mem,
+			 const struct spi_mem_op *op);
+
+int spi_mem_exec_op(struct spi_mem *mem,
+		    const struct spi_mem_op *op);
+
+int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
+				       struct module *owner);
+
+void spi_mem_driver_unregister(struct spi_mem_driver *drv);
+
+#define spi_mem_driver_register(__drv)                                  \
+	spi_mem_driver_register_with_owner(__drv, THIS_MODULE)
+
+#define module_spi_mem_driver(__drv)                                    \
+	module_driver(__drv, spi_mem_driver_register,                   \
+		      spi_mem_driver_unregister)
+
+#endif /* __LINUX_SPI_MEM_H */
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 7b2170bfd6e7..f49b684dc390 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -27,6 +27,7 @@ struct property_entry;
 struct spi_controller;
 struct spi_transfer;
 struct spi_flash_read_message;
+struct spi_controller_mem_ops;
 
 /*
  * INTERFACES between SPI master-side drivers and SPI slave protocol handlers,
@@ -376,6 +377,9 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
  *                    transfer_one callback.
  * @handle_err: the subsystem calls the driver to handle an error that occurs
  *		in the generic implementation of transfer_one_message().
+ * @mem_ops: optimized/dedicated operations for interactions with SPI memory.
+ *	     This field is optional and should only be implemented if the
+ *	     controller has native support for memory like operations.
  * @unprepare_message: undo any work done by prepare_message().
  * @slave_abort: abort the ongoing transfer request on an SPI slave controller
  * @spi_flash_read: to support spi-controller hardwares that provide
@@ -564,6 +568,9 @@ struct spi_controller {
 	void (*handle_err)(struct spi_controller *ctlr,
 			   struct spi_message *message);
 
+	/* Optimized handlers for SPI memory-like operations. */
+	const struct spi_controller_mem_ops *mem_ops;
+
 	/* gpio chip select */
 	int			*cs_gpios;
 
-- 
2.19.0