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>

drivers/spi/Kconfig

@@ -47,6 +47,13 @@ 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

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
 

include/linux/spi/spi-mem.h

+/* 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 */

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;