include/linux/mailbox_controller.h

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License version 2 as
   4  * published by the Free Software Foundation.
   5  */
   6
   7 #ifndef __MAILBOX_CONTROLLER_H
   8 #define __MAILBOX_CONTROLLER_H
   9
  10 #include <linux/of.h>
  11 #include <linux/types.h>
  12 #include <linux/hrtimer.h>
  13 #include <linux/device.h>
  14 #include <linux/completion.h>
  15
  16 struct mbox_chan;
  17
  18 /**
  19  * struct mbox_chan_ops - methods to control mailbox channels
  20  * @send_data:  The API asks the MBOX controller driver, in atomic
  21  *              context try to transmit a message on the bus. Returns 0 if
  22  *              data is accepted for transmission, -EBUSY while rejecting
  23  *              if the remote hasn't yet read the last data sent. Actual
  24  *              transmission of data is reported by the controller via
  25  *              mbox_chan_txdone (if it has some TX ACK irq). It must not
  26  *              sleep.
  27  * @startup:    Called when a client requests the chan. The controller
  28  *              could ask clients for additional parameters of communication
  29  *              to be provided via client's chan_data. This call may
  30  *              block. After this call the Controller must forward any
  31  *              data received on the chan by calling mbox_chan_received_data.
  32  *              The controller may do stuff that need to sleep.
  33  * @shutdown:   Called when a client relinquishes control of a chan.
  34  *              This call may block too. The controller must not forward
  35  *              any received data anymore.
  36  *              The controller may do stuff that need to sleep.
  37  * @last_tx_done: If the controller sets 'txdone_poll', the API calls
  38  *                this to poll status of last TX. The controller must
  39  *                give priority to IRQ method over polling and never
  40  *                set both txdone_poll and txdone_irq. Only in polling
  41  *                mode 'send_data' is expected to return -EBUSY.
  42  *                The controller may do stuff that need to sleep/block.
  43  *                Used only if txdone_poll:=true && txdone_irq:=false
  44  * @peek_data: Atomic check for any received data. Return true if controller
  45  *                has some data to push to the client. False otherwise.
  46  */
  47 struct mbox_chan_ops {
  48         int (*send_data)(struct mbox_chan *chan, void *data);
  49         int (*startup)(struct mbox_chan *chan);
  50         void (*shutdown)(struct mbox_chan *chan);
  51         bool (*last_tx_done)(struct mbox_chan *chan);
  52         bool (*peek_data)(struct mbox_chan *chan);
  53 };
  54
  55 /**
  56  * struct mbox_controller - Controller of a class of communication channels
  57  * @dev:                Device backing this controller
  58  * @ops:                Operators that work on each communication chan
  59  * @chans:              Array of channels
  60  * @num_chans:          Number of channels in the 'chans' array.
  61  * @txdone_irq:         Indicates if the controller can report to API when
  62  *                      the last transmitted data was read by the remote.
  63  *                      Eg, if it has some TX ACK irq.
  64  * @txdone_poll:        If the controller can read but not report the TX
  65  *                      done. Ex, some register shows the TX status but
  66  *                      no interrupt rises. Ignored if 'txdone_irq' is set.
  67  * @txpoll_period:      If 'txdone_poll' is in effect, the API polls for
  68  *                      last TX's status after these many millisecs
  69  * @of_xlate:           Controller driver specific mapping of channel via DT
  70  * @poll_hrt:           API private. hrtimer used to poll for TXDONE on all
  71  *                      channels.
  72  * @node:               API private. To hook into list of controllers.
  73  */
  74 struct mbox_controller {
  75         struct device *dev;
  76         const struct mbox_chan_ops *ops;
  77         struct mbox_chan *chans;
  78         int num_chans;
  79         bool txdone_irq;
  80         bool txdone_poll;
  81         unsigned txpoll_period;
  82         struct mbox_chan *(*of_xlate)(struct mbox_controller *mbox,
  83                                       const struct of_phandle_args *sp);
  84         /* Internal to API */
  85         struct hrtimer poll_hrt;
  86         struct list_head node;
  87 };
  88
  89 /*
  90  * The length of circular buffer for queuing messages from a client.
  91  * 'msg_count' tracks the number of buffered messages while 'msg_free'
  92  * is the index where the next message would be buffered.
  93  * We shouldn't need it too big because every transfer is interrupt
  94  * triggered and if we have lots of data to transfer, the interrupt
  95  * latencies are going to be the bottleneck, not the buffer length.
  96  * Besides, mbox_send_message could be called from atomic context and
  97  * the client could also queue another message from the notifier 'tx_done'
  98  * of the last transfer done.
  99  * REVISIT: If too many platforms see the "Try increasing MBOX_TX_QUEUE_LEN"
 100  * print, it needs to be taken from config option or somesuch.
 101  */
 102 #define MBOX_TX_QUEUE_LEN       20
 103
 104 /**
 105  * struct mbox_chan - s/w representation of a communication chan
 106  * @mbox:               Pointer to the parent/provider of this channel
 107  * @txdone_method:      Way to detect TXDone chosen by the API
 108  * @cl:                 Pointer to the current owner of this channel
 109  * @tx_complete:        Transmission completion
 110  * @active_req:         Currently active request hook
 111  * @msg_count:          No. of mssg currently queued
 112  * @msg_free:           Index of next available mssg slot
 113  * @msg_data:           Hook for data packet
 114  * @lock:               Serialise access to the channel
 115  * @con_priv:           Hook for controller driver to attach private data
 116  */
 117 struct mbox_chan {
 118         struct mbox_controller *mbox;
 119         unsigned txdone_method;
 120         struct mbox_client *cl;
 121         struct completion tx_complete;
 122         void *active_req;
 123         unsigned msg_count, msg_free;
 124         void *msg_data[MBOX_TX_QUEUE_LEN];
 125         spinlock_t lock; /* Serialise access to the channel */
 126         void *con_priv;
 127 };
 128
 129 int mbox_controller_register(struct mbox_controller *mbox); /* can sleep */
 130 void mbox_controller_unregister(struct mbox_controller *mbox); /* can sleep */
 131 void mbox_chan_received_data(struct mbox_chan *chan, void *data); /* atomic */
 132 void mbox_chan_txdone(struct mbox_chan *chan, int r); /* atomic */
 133
 134 #endif /* __MAILBOX_CONTROLLER_H */