text: /* SPDX-License-Identifier: GPL-2.0+ */
  /*
   * Copyright (C) 2018 Álvaro Fernández Rojas <noltari@gmail.com>
   * Copyright (C) 2015 - 2018 Texas Instruments Incorporated <www.ti.com>
   * Written by Mugunthan V N <mugunthanvnm@ti.com>
   *
   */
  
  #ifndef _DMA_H_
  #define _DMA_H_
  
  #include <linux/errno.h>
  #include <linux/types.h>
  
  /*
   * enum dma_direction - dma transfer direction indicator
   * @DMA_MEM_TO_MEM: Memcpy mode
   * @DMA_MEM_TO_DEV: From Memory to Device
   * @DMA_DEV_TO_MEM: From Device to Memory
   * @DMA_DEV_TO_DEV: From Device to Device
   */
  enum dma_direction {
  	DMA_MEM_TO_MEM,
  	DMA_MEM_TO_DEV,
  	DMA_DEV_TO_MEM,
  	DMA_DEV_TO_DEV,
  };
  
  #define DMA_SUPPORTS_MEM_TO_MEM	BIT(0)
  #define DMA_SUPPORTS_MEM_TO_DEV	BIT(1)
  #define DMA_SUPPORTS_DEV_TO_MEM	BIT(2)
  #define DMA_SUPPORTS_DEV_TO_DEV	BIT(3)
  
  /*
   * struct dma_dev_priv - information about a device used by the uclass
   *
   * @supported: mode of transfers that DMA can support, should be
   *	       one/multiple of DMA_SUPPORTS_*
   */
  struct dma_dev_priv {
  	u32 supported;
  };
  
  #ifdef CONFIG_DMA_CHANNELS
  /**
   * A DMA is a feature of computer systems that allows certain hardware
   * subsystems to access main system memory, independent of the CPU.
   * DMA channels are typically generated externally to the HW module
   * consuming them, by an entity this API calls a DMA provider. This API
   * provides a standard means for drivers to enable and disable DMAs, and to
   * copy, send and receive data using DMA.
   *
   * A driver that implements UCLASS_DMA is a DMA provider. A provider will
   * often implement multiple separate DMAs, since the hardware it manages
   * often has this capability. dma_uclass.h describes the interface which
   * DMA providers must implement.
   *
   * DMA consumers/clients are the HW modules driven by the DMA channels. This
   * header file describes the API used by drivers for those HW modules.
   *
   * DMA consumer DMA_MEM_TO_DEV (transmit) usage example (based on networking).
   * Note. dma_send() is sync operation always -  it'll start transfer and will
   * poll for it to complete:
   *	- get/request dma channel
   *	struct dma dma_tx;
   *	ret = dma_get_by_name(common->dev, "tx0", &dma_tx);
   *	if (ret) ...
   *
   *	- enable dma channel
   *	ret = dma_enable(&dma_tx);
   *	if (ret) ...
   *
   *	- dma transmit DMA_MEM_TO_DEV.
   *	struct ti_drv_packet_data packet_data;
   *
   *	packet_data.opt1 = val1;
   *	packet_data.opt2 = val2;
   *	ret = dma_send(&dma_tx, packet, length, &packet_data);
   *	if (ret) ..
   *
   * DMA consumer DMA_DEV_TO_MEM (receive) usage example (based on networking).
   * Note. dma_receive() is sync operation always - it'll start transfer
   * (if required) and will poll for it to complete (or for any previously
   * configured dev2mem transfer to complete):
   *	- get/request dma channel
   *	struct dma dma_rx;
   *	ret = dma_get_by_name(common->dev, "rx0", &dma_rx);
   *	if (ret) ...
   *
   *	- enable dma channel
   *	ret = dma_enable(&dma_rx);
   *	if (ret) ...
   *
   *	- dma receive DMA_DEV_TO_MEM.
   *	struct ti_drv_packet_data packet_data;
   *
   *	len = dma_receive(&dma_rx, (void **)packet, &packet_data);
   *	if (ret < 0) ...
   *
   * DMA consumer DMA_DEV_TO_MEM (receive) zero-copy usage example (based on
   * networking). Networking subsystem allows to configure and use few receive
   * buffers (dev2mem), as Networking RX DMA channels usually implemented
   * as streaming interface
   *	- get/request dma channel
   *	struct dma dma_rx;
   *	ret = dma_get_by_name(common->dev, "rx0", &dma_rx);
   *	if (ret) ...
   *
   *	for (i = 0; i < RX_DESC_NUM; i++) {
   *		ret = dma_prepare_rcv_buf(&dma_rx,
   *					  net_rx_packets[i],
   *					  RX_BUF_SIZE);
   *		if (ret) ...
   *	}
   *
   *	- enable dma channel
   *	ret = dma_enable(&dma_rx);
   *	if (ret) ...
   *
   *	- dma receive DMA_DEV_TO_MEM.
   *	struct ti_drv_packet_data packet_data;
   *
   *	len = dma_receive(&dma_rx, (void **)packet, &packet_data);
   *	if (ret < 0) ..
   *
   *	-- process packet --
   *
   *	- return buffer back to DAM channel
   *	ret = dma_prepare_rcv_buf(&dma_rx,
   *				  net_rx_packets[rx_next],
   *				  RX_BUF_SIZE);
   */
  
  struct udevice;
  
  /**
   * struct dma - A handle to (allowing control of) a single DMA.
   *
   * Clients provide storage for DMA handles. The content of the structure is
   * managed solely by the DMA API and DMA drivers. A DMA struct is
   * initialized by "get"ing the DMA struct. The DMA struct is passed to all
   * other DMA APIs to identify which DMA channel to operate upon.
   *
   * @dev: The device which implements the DMA channel.
   * @id: The DMA channel ID within the provider.
   *
   * Currently, the DMA API assumes that a single integer ID is enough to
   * identify and configure any DMA channel for any DMA provider. If this
   * assumption becomes invalid in the future, the struct could be expanded to
   * either (a) add more fields to allow DMA providers to store additional
   * information, or (b) replace the id field with an opaque pointer, which the
   * provider would dynamically allocated during its .of_xlate op, and process
   * during is .request op. This may require the addition of an extra op to clean
   * up the allocation.
   */
  struct dma {
  	struct udevice *dev;
  	/*
  	 * Written by of_xlate. We assume a single id is enough for now. In the
  	 * future, we might add more fields here.
  	 */
  	unsigned long id;
  };
  
  # if CONFIG_IS_ENABLED(OF_CONTROL) && CONFIG_IS_ENABLED(DMA)
  /**
   * dma_get_by_index - Get/request a DMA by integer index.
   *
   * This looks up and requests a DMA. The index is relative to the client
   * device; each device is assumed to have n DMAs associated with it somehow,
   * and this function finds and requests one of them. The mapping of client
   * device DMA indices to provider DMAs may be via device-tree properties,
   * board-provided mapping tables, or some other mechanism.
   *
   * @dev:	The client device.
   * @index:	The index of the DMA to request, within the client's list of
   *		DMA channels.
   * @dma:	A pointer to a DMA struct to initialize.
   * @return 0 if OK, or a negative error code.
   */
  int dma_get_by_index(struct udevice *dev, int index, struct dma *dma);
  
  /**
   * dma_get_by_name - Get/request a DMA by name.
   *
   * This looks up and requests a DMA. The name is relative to the client
   * device; each device is assumed to have n DMAs associated with it somehow,
   * and this function finds and requests one of them. The mapping of client
   * device DMA names to provider DMAs may be via device-tree properties,
   * board-provided mapping tables, or some other mechanism.
   *
   * @dev:	The client device.
   * @name:	The name of the DMA to request, within the client's list of
   *		DMA channels.
   * @dma:	A pointer to a DMA struct to initialize.
   * @return 0 if OK, or a negative error code.
   */
  int dma_get_by_name(struct udevice *dev, const char *name, struct dma *dma);
  # else
  static inline int dma_get_by_index(struct udevice *dev, int index,
  				   struct dma *dma)
  {
  	return -ENOSYS;
  }
  
  static inline int dma_get_by_name(struct udevice *dev, const char *name,
  				  struct dma *dma)
  {
  	return -ENOSYS;
  }
  # endif
  
  /**
   * dma_request - Request a DMA by provider-specific ID.
   *
   * This requests a DMA using a provider-specific ID. Generally, this function
   * should not be used, since dma_get_by_index/name() provide an interface that
   * better separates clients from intimate knowledge of DMA providers.
   * However, this function may be useful in core SoC-specific code.
   *
   * @dev: The DMA provider device.
   * @dma: A pointer to a DMA struct to initialize. The caller must
   *	 have already initialized any field in this struct which the
   *	 DMA provider uses to identify the DMA channel.
   * @return 0 if OK, or a negative error code.
   */
  int dma_request(struct udevice *dev, struct dma *dma);
  
  /**
   * dma_free - Free a previously requested DMA.
   *
   * @dma: A DMA struct that was previously successfully requested by
   *	 dma_request/get_by_*().
   * @return 0 if OK, or a negative error code.
   */
  int dma_free(struct dma *dma);
  
  /**
   * dma_enable() - Enable (turn on) a DMA channel.
   *
   * @dma: A DMA struct that was previously successfully requested by
   *	 dma_request/get_by_*().
   * @return zero on success, or -ve error code.
   */
  int dma_enable(struct dma *dma);
  
  /**
   * dma_disable() - Disable (turn off) a DMA channel.
   *
   * @dma: A DMA struct that was previously successfully requested by
   *	 dma_request/get_by_*().
   * @return zero on success, or -ve error code.
   */
  int dma_disable(struct dma *dma);
  
  /**
   * dma_prepare_rcv_buf() - Prepare/add receive DMA buffer.
   *
   * It allows to implement zero-copy async DMA_DEV_TO_MEM (receive) transactions
   * if supported by DMA providers.
   *
   * @dma: A DMA struct that was previously successfully requested by
   *	 dma_request/get_by_*().
   * @dst: The receive buffer pointer.
   * @size: The receive buffer size
   * @return zero on success, or -ve error code.
   */
  int dma_prepare_rcv_buf(struct dma *dma, void *dst, size_t size);
  
  /**
   * dma_receive() - Receive a DMA transfer.
   *
   * @dma: A DMA struct that was previously successfully requested by
   *	 dma_request/get_by_*().
   * @dst: The destination pointer.
   * @metadata: DMA driver's channel specific data
   * @return length of received data on success, or zero - no data,
   * or -ve error code.
   */
  int dma_receive(struct dma *dma, void **dst, void *metadata);
  
  /**
   * dma_send() - Send a DMA transfer.
   *
   * @dma: A DMA struct that was previously successfully requested by
   *	 dma_request/get_by_*().
   * @src: The source pointer.
   * @len: Length of the data to be sent (number of bytes).
   * @metadata: DMA driver's channel specific data
   * @return zero on success, or -ve error code.
   */
  int dma_send(struct dma *dma, void *src, size_t len, void *metadata);
  #endif /* CONFIG_DMA_CHANNELS */
  
  /*
   * dma_get_device - get a DMA device which supports transfer
   * type of transfer_type
   *
   * @transfer_type - transfer type should be one/multiple of
   *		    DMA_SUPPORTS_*
   * @devp - udevice pointer to return the found device
   * @return - will return on success and devp will hold the
   *	     pointer to the device
   */
  int dma_get_device(u32 transfer_type, struct udevice **devp);
  
  /*
   * dma_memcpy - try to use DMA to do a mem copy which will be
   *		much faster than CPU mem copy
   *
   * @dst - destination pointer
   * @src - souce pointer
   * @len - data length to be copied
   * @return - on successful transfer returns no of bytes
  	     transferred and on failure return error code.
   */
  int dma_memcpy(void *dst, void *src, size_t len);
  
  #endif	/* _DMA_H_ */
  