2 files changed, 284 insertions, 0 deletions

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 7916e655afc8..b12a7974b665 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -432,6 +432,210 @@ int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
 }
 EXPORT_SYMBOL_GPL(spi_mem_adjust_op_size);
 
+static ssize_t spi_mem_no_dirmap_read(struct spi_mem_dirmap_desc *desc,
+				      u64 offs, size_t len, void *buf)
+{
+	struct spi_mem_op op = desc->info.op_tmpl;
+	int ret;
+
+	op.addr.val = desc->info.offset + offs;
+	op.data.buf.in = buf;
+	op.data.nbytes = len;
+	ret = spi_mem_adjust_op_size(desc->mem, &op);
+	if (ret)
+		return ret;
+
+	ret = spi_mem_exec_op(desc->mem, &op);
+	if (ret)
+		return ret;
+
+	return op.data.nbytes;
+}
+
+static ssize_t spi_mem_no_dirmap_write(struct spi_mem_dirmap_desc *desc,
+				       u64 offs, size_t len, const void *buf)
+{
+	struct spi_mem_op op = desc->info.op_tmpl;
+	int ret;
+
+	op.addr.val = desc->info.offset + offs;
+	op.data.buf.out = buf;
+	op.data.nbytes = len;
+	ret = spi_mem_adjust_op_size(desc->mem, &op);
+	if (ret)
+		return ret;
+
+	ret = spi_mem_exec_op(desc->mem, &op);
+	if (ret)
+		return ret;
+
+	return op.data.nbytes;
+}
+
+/**
+ * spi_mem_dirmap_create() - Create a direct mapping descriptor
+ * @mem: SPI mem device this direct mapping should be created for
+ * @info: direct mapping information
+ *
+ * This function is creating a direct mapping descriptor which can then be used
+ * to access the memory using spi_mem_dirmap_read() or spi_mem_dirmap_write().
+ * If the SPI controller driver does not support direct mapping, this function
+ * fallback to an implementation using spi_mem_exec_op(), so that the caller
+ * doesn't have to bother implementing a fallback on his own.
+ *
+ * Return: a valid pointer in case of success, and ERR_PTR() otherwise.
+ */
+struct spi_mem_dirmap_desc *
+spi_mem_dirmap_create(struct spi_mem *mem,
+		      const struct spi_mem_dirmap_info *info)
+{
+	struct spi_controller *ctlr = mem->spi->controller;
+	struct spi_mem_dirmap_desc *desc;
+	int ret = -ENOTSUPP;
+
+	/* Make sure the number of address cycles is between 1 and 8 bytes. */
+	if (!info->op_tmpl.addr.nbytes || info->op_tmpl.addr.nbytes > 8)
+		return ERR_PTR(-EINVAL);
+
+	/* data.dir should either be SPI_MEM_DATA_IN or SPI_MEM_DATA_OUT. */
+	if (info->op_tmpl.data.dir == SPI_MEM_NO_DATA)
+		return ERR_PTR(-EINVAL);
+
+	desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+	if (!desc)
+		return ERR_PTR(-ENOMEM);
+
+	desc->mem = mem;
+	desc->info = *info;
+	if (ctlr->mem_ops && ctlr->mem_ops->dirmap_create)
+		ret = ctlr->mem_ops->dirmap_create(desc);
+
+	if (ret) {
+		desc->nodirmap = true;
+		if (!spi_mem_supports_op(desc->mem, &desc->info.op_tmpl))
+			ret = -ENOTSUPP;
+		else
+			ret = 0;
+	}
+
+	if (ret) {
+		kfree(desc);
+		return ERR_PTR(ret);
+	}
+
+	return desc;
+}
+EXPORT_SYMBOL_GPL(spi_mem_dirmap_create);
+
+/**
+ * spi_mem_dirmap_destroy() - Destroy a direct mapping descriptor
+ * @desc: the direct mapping descriptor to destroy
+ * @info: direct mapping information
+ *
+ * This function destroys a direct mapping descriptor previously created by
+ * spi_mem_dirmap_create().
+ */
+void spi_mem_dirmap_destroy(struct spi_mem_dirmap_desc *desc)
+{
+	struct spi_controller *ctlr = desc->mem->spi->controller;
+
+	if (!desc->nodirmap && ctlr->mem_ops && ctlr->mem_ops->dirmap_destroy)
+		ctlr->mem_ops->dirmap_destroy(desc);
+}
+EXPORT_SYMBOL_GPL(spi_mem_dirmap_destroy);
+
+/**
+ * spi_mem_dirmap_dirmap_read() - Read data through a direct mapping
+ * @desc: direct mapping descriptor
+ * @offs: offset to start reading from. Note that this is not an absolute
+ *	  offset, but the offset within the direct mapping which already has
+ *	  its own offset
+ * @len: length in bytes
+ * @buf: destination buffer. This buffer must be DMA-able
+ *
+ * This function reads data from a memory device using a direct mapping
+ * previously instantiated with spi_mem_dirmap_create().
+ *
+ * Return: the amount of data read from the memory device or a negative error
+ * code. Note that the returned size might be smaller than @len, and the caller
+ * is responsible for calling spi_mem_dirmap_read() again when that happens.
+ */
+ssize_t spi_mem_dirmap_read(struct spi_mem_dirmap_desc *desc,
+			    u64 offs, size_t len, void *buf)
+{
+	struct spi_controller *ctlr = desc->mem->spi->controller;
+	ssize_t ret;
+
+	if (desc->info.op_tmpl.data.dir != SPI_MEM_DATA_IN)
+		return -EINVAL;
+
+	if (!len)
+		return 0;
+
+	if (desc->nodirmap) {
+		ret = spi_mem_no_dirmap_read(desc, offs, len, buf);
+	} else if (ctlr->mem_ops && ctlr->mem_ops->dirmap_read) {
+		ret = spi_mem_access_start(desc->mem);
+		if (ret)
+			return ret;
+
+		ret = ctlr->mem_ops->dirmap_read(desc, offs, len, buf);
+
+		spi_mem_access_end(desc->mem);
+	} else {
+		ret = -ENOTSUPP;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_mem_dirmap_read);
+
+/**
+ * spi_mem_dirmap_dirmap_write() - Write data through a direct mapping
+ * @desc: direct mapping descriptor
+ * @offs: offset to start writing from. Note that this is not an absolute
+ *	  offset, but the offset within the direct mapping which already has
+ *	  its own offset
+ * @len: length in bytes
+ * @buf: source buffer. This buffer must be DMA-able
+ *
+ * This function writes data to a memory device using a direct mapping
+ * previously instantiated with spi_mem_dirmap_create().
+ *
+ * Return: the amount of data written to the memory device or a negative error
+ * code. Note that the returned size might be smaller than @len, and the caller
+ * is responsible for calling spi_mem_dirmap_write() again when that happens.
+ */
+ssize_t spi_mem_dirmap_write(struct spi_mem_dirmap_desc *desc,
+			     u64 offs, size_t len, const void *buf)
+{
+	struct spi_controller *ctlr = desc->mem->spi->controller;
+	ssize_t ret;
+
+	if (desc->info.op_tmpl.data.dir != SPI_MEM_DATA_OUT)
+		return -EINVAL;
+
+	if (!len)
+		return 0;
+
+	if (desc->nodirmap) {
+		ret = spi_mem_no_dirmap_write(desc, offs, len, buf);
+	} else if (ctlr->mem_ops && ctlr->mem_ops->dirmap_write) {
+		ret = spi_mem_access_start(desc->mem);
+		if (ret)
+			return ret;
+
+		ret = ctlr->mem_ops->dirmap_write(desc, offs, len, buf);
+
+		spi_mem_access_end(desc->mem);
+	} else {
+		ret = -ENOTSUPP;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_mem_dirmap_write);
+
 static inline struct spi_mem_driver *to_spi_mem_drv(struct device_driver *drv)
 {
 	return container_of(drv, struct spi_mem_driver, spidrv.driver);
diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
index 250b6f5c47c2..3fe24500c5ee 100644
--- a/include/linux/spi/spi-mem.h
+++ b/include/linux/spi/spi-mem.h
@@ -125,6 +125,49 @@ struct spi_mem_op {
 	}
 
 /**
+ * struct spi_mem_dirmap_info - Direct mapping information
+ * @op_tmpl: operation template that should be used by the direct mapping when
+ *	     the memory device is accessed
+ * @offset: absolute offset this direct mapping is pointing to
+ * @length: length in byte of this direct mapping
+ *
+ * These information are used by the controller specific implementation to know
+ * the portion of memory that is directly mapped and the spi_mem_op that should
+ * be used to access the device.
+ * A direct mapping is only valid for one direction (read or write) and this
+ * direction is directly encoded in the ->op_tmpl.data.dir field.
+ */
+struct spi_mem_dirmap_info {
+	struct spi_mem_op op_tmpl;
+	u64 offset;
+	u64 length;
+};
+
+/**
+ * struct spi_mem_dirmap_desc - Direct mapping descriptor
+ * @mem: the SPI memory device this direct mapping is attached to
+ * @info: information passed at direct mapping creation time
+ * @nodirmap: set to 1 if the SPI controller does not implement
+ *	      ->mem_ops->dirmap_create() or when this function returned an
+ *	      error. If @nodirmap is true, all spi_mem_dirmap_{read,write}()
+ *	      calls will use spi_mem_exec_op() to access the memory. This is a
+ *	      degraded mode that allows spi_mem drivers to use the same code
+ *	      no matter whether the controller supports direct mapping or not
+ * @priv: field pointing to controller specific data
+ *
+ * Common part of a direct mapping descriptor. This object is created by
+ * spi_mem_dirmap_create() and controller implementation of ->create_dirmap()
+ * can create/attach direct mapping resources to the descriptor in the ->priv
+ * field.
+ */
+struct spi_mem_dirmap_desc {
+	struct spi_mem *mem;
+	struct spi_mem_dirmap_info info;
+	unsigned int nodirmap;
+	void *priv;
+};
+
+/**
  * struct spi_mem - describes a SPI memory device
  * @spi: the underlying SPI device
  * @drvpriv: spi_mem_driver private data
@@ -179,10 +222,32 @@ static inline void *spi_mem_get_drvdata(struct spi_mem *mem)
  *	      Note that if the implementation of this function allocates memory
  *	      dynamically, then it should do so with devm_xxx(), as we don't
  *	      have a ->free_name() function.
+ * @dirmap_create: create a direct mapping descriptor that can later be used to
+ *		   access the memory device. This method is optional
+ * @dirmap_destroy: destroy a memory descriptor previous created by
+ *		    ->dirmap_create()
+ * @dirmap_read: read data from the memory device using the direct mapping
+ *		 created by ->dirmap_create(). The function can return less
+ *		 data than requested (for example when the request is crossing
+ *		 the currently mapped area), and the caller of
+ *		 spi_mem_dirmap_read() is responsible for calling it again in
+ *		 this case.
+ * @dirmap_write: write data to the memory device using the direct mapping
+ *		  created by ->dirmap_create(). The function can return less
+ *		  data than requested (for example when the request is crossing
+ *		  the currently mapped area), and the caller of
+ *		  spi_mem_dirmap_write() is responsible for calling it again in
+ *		  this case.
  *
  * 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.
+ *
+ * Note on ->dirmap_{read,write}(): drivers should avoid accessing the direct
+ * mapping from the CPU because doing that can stall the CPU waiting for the
+ * SPI mem transaction to finish, and this will make real-time maintainers
+ * unhappy and might make your system less reactive. Instead, drivers should
+ * use DMA to access this direct mapping.
  */
 struct spi_controller_mem_ops {
 	int (*adjust_op_size)(struct spi_mem *mem, struct spi_mem_op *op);
@@ -191,6 +256,12 @@ struct spi_controller_mem_ops {
 	int (*exec_op)(struct spi_mem *mem,
 		       const struct spi_mem_op *op);
 	const char *(*get_name)(struct spi_mem *mem);
+	int (*dirmap_create)(struct spi_mem_dirmap_desc *desc);
+	void (*dirmap_destroy)(struct spi_mem_dirmap_desc *desc);
+	ssize_t (*dirmap_read)(struct spi_mem_dirmap_desc *desc,
+			       u64 offs, size_t len, void *buf);
+	ssize_t (*dirmap_write)(struct spi_mem_dirmap_desc *desc,
+				u64 offs, size_t len, const void *buf);
 };
 
 /**
@@ -251,6 +322,15 @@ int spi_mem_exec_op(struct spi_mem *mem,
 
 const char *spi_mem_get_name(struct spi_mem *mem);
 
+struct spi_mem_dirmap_desc *
+spi_mem_dirmap_create(struct spi_mem *mem,
+		      const struct spi_mem_dirmap_info *info);
+void spi_mem_dirmap_destroy(struct spi_mem_dirmap_desc *desc);
+ssize_t spi_mem_dirmap_read(struct spi_mem_dirmap_desc *desc,
+			    u64 offs, size_t len, void *buf);
+ssize_t spi_mem_dirmap_write(struct spi_mem_dirmap_desc *desc,
+			     u64 offs, size_t len, const void *buf);
+
 int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
 				       struct module *owner);