^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) ============================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) The Common Mailbox Framework
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ============================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) :Author: Jassi Brar <jaswinder.singh@linaro.org>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) This document aims to help developers write client and controller
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) drivers for the API. But before we start, let us note that the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) client (especially) and controller drivers are likely going to be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) very platform specific because the remote firmware is likely to be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) proprietary and implement non-standard protocol. So even if two
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) platforms employ, say, PL320 controller, the client drivers can't
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) be shared across them. Even the PL320 driver might need to accommodate
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) some platform specific quirks. So the API is meant mainly to avoid
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) similar copies of code written for each platform. Having said that,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) nothing prevents the remote f/w to also be Linux based and use the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) same api there. However none of that helps us locally because we only
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) ever deal at client's protocol level.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) Some of the choices made during implementation are the result of this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) peculiarity of this "common" framework.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) Controller Driver (See include/linux/mailbox_controller.h)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) ==========================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) Allocate mbox_controller and the array of mbox_chan.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) Populate mbox_chan_ops, except peek_data() all are mandatory.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) The controller driver might know a message has been consumed
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) by the remote by getting an IRQ or polling some hardware flag
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) or it can never know (the client knows by way of the protocol).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) The method in order of preference is IRQ -> Poll -> None, which
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) the controller driver should set via 'txdone_irq' or 'txdone_poll'
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) or neither.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) Client Driver (See include/linux/mailbox_client.h)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) ==================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) The client might want to operate in blocking mode (synchronously
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) send a message through before returning) or non-blocking/async mode (submit
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) a message and a callback function to the API and return immediately).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) struct demo_client {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) struct mbox_client cl;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) struct mbox_chan *mbox;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) struct completion c;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) bool async;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) /* ... */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) * This is the handler for data received from remote. The behaviour is purely
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) * dependent upon the protocol. This is just an example.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) static void message_from_remote(struct mbox_client *cl, void *mssg)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) struct demo_client *dc = container_of(cl, struct demo_client, cl);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) if (dc->async) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) if (is_an_ack(mssg)) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) /* An ACK to our last sample sent */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) return; /* Or do something else here */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) } else { /* A new message from remote */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) queue_req(mssg);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) } else {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) /* Remote f/w sends only ACK packets on this channel */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) return;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) static void sample_sent(struct mbox_client *cl, void *mssg, int r)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) struct demo_client *dc = container_of(cl, struct demo_client, cl);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) complete(&dc->c);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) static void client_demo(struct platform_device *pdev)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) struct demo_client *dc_sync, *dc_async;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) /* The controller already knows async_pkt and sync_pkt */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) struct async_pkt ap;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) struct sync_pkt sp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) dc_sync = kzalloc(sizeof(*dc_sync), GFP_KERNEL);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) dc_async = kzalloc(sizeof(*dc_async), GFP_KERNEL);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) /* Populate non-blocking mode client */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) dc_async->cl.dev = &pdev->dev;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) dc_async->cl.rx_callback = message_from_remote;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) dc_async->cl.tx_done = sample_sent;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) dc_async->cl.tx_block = false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) dc_async->cl.tx_tout = 0; /* doesn't matter here */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99) dc_async->cl.knows_txdone = false; /* depending upon protocol */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) dc_async->async = true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) init_completion(&dc_async->c);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) /* Populate blocking mode client */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) dc_sync->cl.dev = &pdev->dev;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) dc_sync->cl.rx_callback = message_from_remote;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) dc_sync->cl.tx_done = NULL; /* operate in blocking mode */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) dc_sync->cl.tx_block = true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) dc_sync->cl.tx_tout = 500; /* by half a second */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) dc_sync->cl.knows_txdone = false; /* depending upon protocol */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) dc_sync->async = false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) /* ASync mailbox is listed second in 'mboxes' property */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) dc_async->mbox = mbox_request_channel(&dc_async->cl, 1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) /* Populate data packet */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) /* ap.xxx = 123; etc */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) /* Send async message to remote */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) mbox_send_message(dc_async->mbox, &ap);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) /* Sync mailbox is listed first in 'mboxes' property */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) dc_sync->mbox = mbox_request_channel(&dc_sync->cl, 0);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) /* Populate data packet */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) /* sp.abc = 123; etc */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) /* Send message to remote in blocking mode */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) mbox_send_message(dc_sync->mbox, &sp);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) /* At this point 'sp' has been sent */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) /* Now wait for async chan to be done */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) wait_for_completion(&dc_async->c);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) }
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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