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129 lines
4.4 KiB
129 lines
4.4 KiB
============================ |
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The Common Mailbox Framework |
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============================ |
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:Author: Jassi Brar <[email protected]> |
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This document aims to help developers write client and controller |
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drivers for the API. But before we start, let us note that the |
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client (especially) and controller drivers are likely going to be |
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very platform specific because the remote firmware is likely to be |
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proprietary and implement non-standard protocol. So even if two |
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platforms employ, say, PL320 controller, the client drivers can't |
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be shared across them. Even the PL320 driver might need to accommodate |
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some platform specific quirks. So the API is meant mainly to avoid |
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similar copies of code written for each platform. Having said that, |
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nothing prevents the remote f/w to also be Linux based and use the |
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same api there. However none of that helps us locally because we only |
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ever deal at client's protocol level. |
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Some of the choices made during implementation are the result of this |
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peculiarity of this "common" framework. |
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Controller Driver (See include/linux/mailbox_controller.h) |
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========================================================== |
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Allocate mbox_controller and the array of mbox_chan. |
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Populate mbox_chan_ops, except peek_data() all are mandatory. |
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The controller driver might know a message has been consumed |
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by the remote by getting an IRQ or polling some hardware flag |
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or it can never know (the client knows by way of the protocol). |
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The method in order of preference is IRQ -> Poll -> None, which |
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the controller driver should set via 'txdone_irq' or 'txdone_poll' |
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or neither. |
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Client Driver (See include/linux/mailbox_client.h) |
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================================================== |
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The client might want to operate in blocking mode (synchronously |
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send a message through before returning) or non-blocking/async mode (submit |
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a message and a callback function to the API and return immediately). |
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:: |
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struct demo_client { |
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struct mbox_client cl; |
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struct mbox_chan *mbox; |
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struct completion c; |
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bool async; |
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/* ... */ |
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}; |
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/* |
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* This is the handler for data received from remote. The behaviour is purely |
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* dependent upon the protocol. This is just an example. |
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*/ |
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static void message_from_remote(struct mbox_client *cl, void *mssg) |
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{ |
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struct demo_client *dc = container_of(cl, struct demo_client, cl); |
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if (dc->async) { |
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if (is_an_ack(mssg)) { |
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/* An ACK to our last sample sent */ |
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return; /* Or do something else here */ |
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} else { /* A new message from remote */ |
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queue_req(mssg); |
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} |
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} else { |
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/* Remote f/w sends only ACK packets on this channel */ |
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return; |
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} |
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} |
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static void sample_sent(struct mbox_client *cl, void *mssg, int r) |
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{ |
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struct demo_client *dc = container_of(cl, struct demo_client, cl); |
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complete(&dc->c); |
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} |
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static void client_demo(struct platform_device *pdev) |
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{ |
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struct demo_client *dc_sync, *dc_async; |
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/* The controller already knows async_pkt and sync_pkt */ |
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struct async_pkt ap; |
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struct sync_pkt sp; |
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dc_sync = kzalloc(sizeof(*dc_sync), GFP_KERNEL); |
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dc_async = kzalloc(sizeof(*dc_async), GFP_KERNEL); |
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/* Populate non-blocking mode client */ |
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dc_async->cl.dev = &pdev->dev; |
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dc_async->cl.rx_callback = message_from_remote; |
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dc_async->cl.tx_done = sample_sent; |
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dc_async->cl.tx_block = false; |
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dc_async->cl.tx_tout = 0; /* doesn't matter here */ |
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dc_async->cl.knows_txdone = false; /* depending upon protocol */ |
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dc_async->async = true; |
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init_completion(&dc_async->c); |
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/* Populate blocking mode client */ |
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dc_sync->cl.dev = &pdev->dev; |
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dc_sync->cl.rx_callback = message_from_remote; |
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dc_sync->cl.tx_done = NULL; /* operate in blocking mode */ |
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dc_sync->cl.tx_block = true; |
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dc_sync->cl.tx_tout = 500; /* by half a second */ |
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dc_sync->cl.knows_txdone = false; /* depending upon protocol */ |
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dc_sync->async = false; |
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/* ASync mailbox is listed second in 'mboxes' property */ |
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dc_async->mbox = mbox_request_channel(&dc_async->cl, 1); |
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/* Populate data packet */ |
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/* ap.xxx = 123; etc */ |
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/* Send async message to remote */ |
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mbox_send_message(dc_async->mbox, &ap); |
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/* Sync mailbox is listed first in 'mboxes' property */ |
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dc_sync->mbox = mbox_request_channel(&dc_sync->cl, 0); |
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/* Populate data packet */ |
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/* sp.abc = 123; etc */ |
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/* Send message to remote in blocking mode */ |
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mbox_send_message(dc_sync->mbox, &sp); |
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/* At this point 'sp' has been sent */ |
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/* Now wait for async chan to be done */ |
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wait_for_completion(&dc_async->c); |
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}
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