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authorLinus Torvalds <torvalds@linux-foundation.org>2014-10-21 11:21:19 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-21 11:21:19 -0700
commit43d451f163c1b615c1bedef95258c49712679eeb (patch)
tree52ed78b04435ffbd663a902bbd5bdb69a65ad584 /Documentation
parent21d2271fd0812ebe3716cab0b48356837485a74d (diff)
parent9f3e3cacb2ffdefe28c7cf490bf543e4dcb2770a (diff)
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Merge branch 'mailbox-for-linus' of git://git.linaro.org/landing-teams/working/fujitsu/integration
Pull mailbox framework from Jassi Brar: "A framework for Mailbox controllers and clients have been cooking for more than a year now. Everybody in the CC list had been copied on patchset revisions and most of them have made sounds of approval, though just one concrete Reviewed-by. The patchset has also been in linux-next for a couple of weeks now and no conflict has been reported. The framework has the backing of at least 5 platforms, though I can't say if/when they upstream their drivers (some businesses have 'changed')" (Further acked-by by Arnd Bergmann and Suman Anna in the pull request thread) * 'mailbox-for-linus' of git://git.linaro.org/landing-teams/working/fujitsu/integration: dt: mailbox: add generic bindings doc: add documentation for mailbox framework mailbox: Introduce framework for mailbox mailbox: rename pl320-ipc specific mailbox.h
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/devicetree/bindings/mailbox/mailbox.txt38
-rw-r--r--Documentation/mailbox.txt122
2 files changed, 160 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/mailbox/mailbox.txt b/Documentation/devicetree/bindings/mailbox/mailbox.txt
new file mode 100644
index 000000000000..1a2cd3d266db
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/mailbox.txt
@@ -0,0 +1,38 @@
+* Generic Mailbox Controller and client driver bindings
+
+Generic binding to provide a way for Mailbox controller drivers to
+assign appropriate mailbox channel to client drivers.
+
+* Mailbox Controller
+
+Required property:
+- #mbox-cells: Must be at least 1. Number of cells in a mailbox
+ specifier.
+
+Example:
+ mailbox: mailbox {
+ ...
+ #mbox-cells = <1>;
+ };
+
+
+* Mailbox Client
+
+Required property:
+- mboxes: List of phandle and mailbox channel specifiers.
+
+Optional property:
+- mbox-names: List of identifier strings for each mailbox channel
+ required by the client. The use of this property
+ is discouraged in favor of using index in list of
+ 'mboxes' while requesting a mailbox. Instead the
+ platforms may define channel indices, in DT headers,
+ to something legible.
+
+Example:
+ pwr_cntrl: power {
+ ...
+ mbox-names = "pwr-ctrl", "rpc";
+ mboxes = <&mailbox 0
+ &mailbox 1>;
+ };
diff --git a/Documentation/mailbox.txt b/Documentation/mailbox.txt
new file mode 100644
index 000000000000..60f43ff629aa
--- /dev/null
+++ b/Documentation/mailbox.txt
@@ -0,0 +1,122 @@
+ The Common Mailbox Framework
+ Jassi Brar <jaswinder.singh@linaro.org>
+
+ This document aims to help developers write client and controller
+drivers for the API. But before we start, let us note that the
+client (especially) and controller drivers are likely going to be
+very platform specific because the remote firmware is likely to be
+proprietary and implement non-standard protocol. So even if two
+platforms employ, say, PL320 controller, the client drivers can't
+be shared across them. Even the PL320 driver might need to accommodate
+some platform specific quirks. So the API is meant mainly to avoid
+similar copies of code written for each platform. Having said that,
+nothing prevents the remote f/w to also be Linux based and use the
+same api there. However none of that helps us locally because we only
+ever deal at client's protocol level.
+ Some of the choices made during implementation are the result of this
+peculiarity of this "common" framework.
+
+
+
+ Part 1 - Controller Driver (See include/linux/mailbox_controller.h)
+
+ Allocate mbox_controller and the array of mbox_chan.
+Populate mbox_chan_ops, except peek_data() all are mandatory.
+The controller driver might know a message has been consumed
+by the remote by getting an IRQ or polling some hardware flag
+or it can never know (the client knows by way of the protocol).
+The method in order of preference is IRQ -> Poll -> None, which
+the controller driver should set via 'txdone_irq' or 'txdone_poll'
+or neither.
+
+
+ Part 2 - Client Driver (See include/linux/mailbox_client.h)
+
+ The client might want to operate in blocking mode (synchronously
+send a message through before returning) or non-blocking/async mode (submit
+a message and a callback function to the API and return immediately).
+
+
+struct demo_client {
+ struct mbox_client cl;
+ struct mbox_chan *mbox;
+ struct completion c;
+ bool async;
+ /* ... */
+};
+
+/*
+ * This is the handler for data received from remote. The behaviour is purely
+ * dependent upon the protocol. This is just an example.
+ */
+static void message_from_remote(struct mbox_client *cl, void *mssg)
+{
+ struct demo_client *dc = container_of(mbox_client,
+ struct demo_client, cl);
+ if (dc->aysnc) {
+ if (is_an_ack(mssg)) {
+ /* An ACK to our last sample sent */
+ return; /* Or do something else here */
+ } else { /* A new message from remote */
+ queue_req(mssg);
+ }
+ } else {
+ /* Remote f/w sends only ACK packets on this channel */
+ return;
+ }
+}
+
+static void sample_sent(struct mbox_client *cl, void *mssg, int r)
+{
+ struct demo_client *dc = container_of(mbox_client,
+ struct demo_client, cl);
+ complete(&dc->c);
+}
+
+static void client_demo(struct platform_device *pdev)
+{
+ struct demo_client *dc_sync, *dc_async;
+ /* The controller already knows async_pkt and sync_pkt */
+ struct async_pkt ap;
+ struct sync_pkt sp;
+
+ dc_sync = kzalloc(sizeof(*dc_sync), GFP_KERNEL);
+ dc_async = kzalloc(sizeof(*dc_async), GFP_KERNEL);
+
+ /* Populate non-blocking mode client */
+ dc_async->cl.dev = &pdev->dev;
+ dc_async->cl.rx_callback = message_from_remote;
+ dc_async->cl.tx_done = sample_sent;
+ dc_async->cl.tx_block = false;
+ dc_async->cl.tx_tout = 0; /* doesn't matter here */
+ dc_async->cl.knows_txdone = false; /* depending upon protocol */
+ dc_async->async = true;
+ init_completion(&dc_async->c);
+
+ /* Populate blocking mode client */
+ dc_sync->cl.dev = &pdev->dev;
+ dc_sync->cl.rx_callback = message_from_remote;
+ dc_sync->cl.tx_done = NULL; /* operate in blocking mode */
+ dc_sync->cl.tx_block = true;
+ dc_sync->cl.tx_tout = 500; /* by half a second */
+ dc_sync->cl.knows_txdone = false; /* depending upon protocol */
+ dc_sync->async = false;
+
+ /* ASync mailbox is listed second in 'mboxes' property */
+ dc_async->mbox = mbox_request_channel(&dc_async->cl, 1);
+ /* Populate data packet */
+ /* ap.xxx = 123; etc */
+ /* Send async message to remote */
+ mbox_send_message(dc_async->mbox, &ap);
+
+ /* Sync mailbox is listed first in 'mboxes' property */
+ dc_sync->mbox = mbox_request_channel(&dc_sync->cl, 0);
+ /* Populate data packet */
+ /* sp.abc = 123; etc */
+ /* Send message to remote in blocking mode */
+ mbox_send_message(dc_sync->mbox, &sp);
+ /* At this point 'sp' has been sent */
+
+ /* Now wait for async chan to be done */
+ wait_for_completion(&dc_async->c);
+}