diff options
Diffstat (limited to 'Documentation')
17 files changed, 437 insertions, 36 deletions
diff --git a/Documentation/DocBook/media/v4l/compat.xml b/Documentation/DocBook/media/v4l/compat.xml index eee6f0f4aa43..3a626d1b8f2e 100644 --- a/Documentation/DocBook/media/v4l/compat.xml +++ b/Documentation/DocBook/media/v4l/compat.xml @@ -2545,6 +2545,30 @@ fields changed from _s32 to _u32. </orderedlist> </section> + <section> + <title>V4L2 in Linux 3.16</title> + <orderedlist> + <listitem> + <para>Added event V4L2_EVENT_SOURCE_CHANGE. + </para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 3.17</title> + <orderedlist> + <listitem> + <para>Extended &v4l2-pix-format;. Added format flags. + </para> + </listitem> + <listitem> + <para>Added compound control types and &VIDIOC-QUERY-EXT-CTRL;. + </para> + </listitem> + </orderedlist> + </section> + <section id="other"> <title>Relation of V4L2 to other Linux multimedia APIs</title> diff --git a/Documentation/DocBook/media/v4l/func-poll.xml b/Documentation/DocBook/media/v4l/func-poll.xml index 85cad8bff5ba..4c73f115219b 100644 --- a/Documentation/DocBook/media/v4l/func-poll.xml +++ b/Documentation/DocBook/media/v4l/func-poll.xml @@ -29,9 +29,12 @@ can suspend execution until the driver has captured data or is ready to accept data for output.</para> <para>When streaming I/O has been negotiated this function waits -until a buffer has been filled or displayed and can be dequeued with -the &VIDIOC-DQBUF; ioctl. When buffers are already in the outgoing -queue of the driver the function returns immediately.</para> +until a buffer has been filled by the capture device and can be dequeued +with the &VIDIOC-DQBUF; ioctl. For output devices this function waits +until the device is ready to accept a new buffer to be queued up with +the &VIDIOC-QBUF; ioctl for display. When buffers are already in the outgoing +queue of the driver (capture) or the incoming queue isn't full (display) +the function returns immediately.</para> <para>On success <function>poll()</function> returns the number of file descriptors that have been selected (that is, file descriptors @@ -44,10 +47,22 @@ Capture devices set the <constant>POLLIN</constant> and flags. When the function timed out it returns a value of zero, on failure it returns <returnvalue>-1</returnvalue> and the <varname>errno</varname> variable is set appropriately. When the -application did not call &VIDIOC-QBUF; or &VIDIOC-STREAMON; yet the +application did not call &VIDIOC-STREAMON; the <function>poll()</function> function succeeds, but sets the <constant>POLLERR</constant> flag in the -<structfield>revents</structfield> field.</para> +<structfield>revents</structfield> field. When the +application has called &VIDIOC-STREAMON; for a capture device but hasn't +yet called &VIDIOC-QBUF;, the <function>poll()</function> function +succeeds and sets the <constant>POLLERR</constant> flag in the +<structfield>revents</structfield> field. For output devices this +same situation will cause <function>poll()</function> to succeed +as well, but it sets the <constant>POLLOUT</constant> and +<constant>POLLWRNORM</constant> flags in the <structfield>revents</structfield> +field.</para> + + <para>If an event occurred (see &VIDIOC-DQEVENT;) then +<constant>POLLPRI</constant> will be set in the <structfield>revents</structfield> +field and <function>poll()</function> will return.</para> <para>When use of the <function>read()</function> function has been negotiated and the driver does not capture yet, the @@ -58,10 +73,18 @@ continuously (as opposed to, for example, still images) the function may return immediately.</para> <para>When use of the <function>write()</function> function has -been negotiated the <function>poll</function> function just waits +been negotiated and the driver does not stream yet, the +<function>poll</function> function starts streaming. When that fails +it returns a <constant>POLLERR</constant> as above. Otherwise it waits until the driver is ready for a non-blocking <function>write()</function> call.</para> + <para>If the caller is only interested in events (just +<constant>POLLPRI</constant> is set in the <structfield>events</structfield> +field), then <function>poll()</function> will <emphasis>not</emphasis> +start streaming if the driver does not stream yet. This makes it +possible to just poll for events and not for buffers.</para> + <para>All drivers implementing the <function>read()</function> or <function>write()</function> function or streaming I/O must also support the <function>poll()</function> function.</para> diff --git a/Documentation/DocBook/media/v4l/v4l2.xml b/Documentation/DocBook/media/v4l/v4l2.xml index f2f81f06a17b..7cfe618f754d 100644 --- a/Documentation/DocBook/media/v4l/v4l2.xml +++ b/Documentation/DocBook/media/v4l/v4l2.xml @@ -152,10 +152,11 @@ structs, ioctls) must be noted in more detail in the history chapter applications. --> <revision> - <revnumber>3.16</revnumber> - <date>2014-05-27</date> - <authorinitials>lp</authorinitials> - <revremark>Extended &v4l2-pix-format;. Added format flags. + <revnumber>3.17</revnumber> + <date>2014-08-04</date> + <authorinitials>lp, hv</authorinitials> + <revremark>Extended &v4l2-pix-format;. Added format flags. Added compound control types +and VIDIOC_QUERY_EXT_CTRL. </revremark> </revision> @@ -538,7 +539,7 @@ and discussions on the V4L mailing list.</revremark> </partinfo> <title>Video for Linux Two API Specification</title> - <subtitle>Revision 3.14</subtitle> + <subtitle>Revision 3.17</subtitle> <chapter id="common"> &sub-common; diff --git a/Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml b/Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml index 1ba9e999af3f..c62a7360719b 100644 --- a/Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml +++ b/Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml @@ -119,7 +119,7 @@ </row> <row> <entry>&v4l2-rect;</entry> - <entry><structfield>rect</structfield></entry> + <entry><structfield>r</structfield></entry> <entry>Selection rectangle, in pixels.</entry> </row> <row> diff --git a/Documentation/cgroups/cpusets.txt b/Documentation/cgroups/cpusets.txt index 7740038d82bc..3c94ff3f9693 100644 --- a/Documentation/cgroups/cpusets.txt +++ b/Documentation/cgroups/cpusets.txt @@ -345,14 +345,14 @@ the named feature on. The implementation is simple. Setting the flag 'cpuset.memory_spread_page' turns on a per-process flag -PF_SPREAD_PAGE for each task that is in that cpuset or subsequently +PFA_SPREAD_PAGE for each task that is in that cpuset or subsequently joins that cpuset. The page allocation calls for the page cache -is modified to perform an inline check for this PF_SPREAD_PAGE task +is modified to perform an inline check for this PFA_SPREAD_PAGE task flag, and if set, a call to a new routine cpuset_mem_spread_node() returns the node to prefer for the allocation. Similarly, setting 'cpuset.memory_spread_slab' turns on the flag -PF_SPREAD_SLAB, and appropriately marked slab caches will allocate +PFA_SPREAD_SLAB, and appropriately marked slab caches will allocate pages from the node returned by cpuset_mem_spread_node(). The cpuset_mem_spread_node() routine is also simple. It uses the diff --git a/Documentation/devicetree/bindings/dma/rcar-audmapp.txt b/Documentation/devicetree/bindings/dma/rcar-audmapp.txt index 9f1d750d76de..61bca509d7b9 100644 --- a/Documentation/devicetree/bindings/dma/rcar-audmapp.txt +++ b/Documentation/devicetree/bindings/dma/rcar-audmapp.txt @@ -16,9 +16,9 @@ Example: * DMA client Required properties: -- dmas: a list of <[DMA multiplexer phandle] [SRS/DRS value]> pairs, - where SRS/DRS values are fixed handles, specified in the SoC - manual as the value that would be written into the PDMACHCR. +- dmas: a list of <[DMA multiplexer phandle] [SRS << 8 | DRS]> pairs. + where SRS/DRS are specified in the SoC manual. + It will be written into PDMACHCR as high 16-bit parts. - dma-names: a list of DMA channel names, one per "dmas" entry Example: diff --git a/Documentation/devicetree/bindings/input/atmel,maxtouch.txt b/Documentation/devicetree/bindings/input/atmel,maxtouch.txt index 0ac23f2ed104..1852906517ab 100644 --- a/Documentation/devicetree/bindings/input/atmel,maxtouch.txt +++ b/Documentation/devicetree/bindings/input/atmel,maxtouch.txt @@ -11,10 +11,6 @@ Required properties: Optional properties for main touchpad device: -- linux,gpio-keymap: An array of up to 4 entries indicating the Linux - keycode generated by each GPIO. Linux keycodes are defined in - <dt-bindings/input/input.h>. - - linux,gpio-keymap: When enabled, the SPT_GPIOPWN_T19 object sends messages on GPIO bit changes. An array of up to 8 entries can be provided indicating the Linux keycode mapped to each bit of the status byte, diff --git a/Documentation/devicetree/bindings/net/stmmac.txt b/Documentation/devicetree/bindings/net/stmmac.txt index 9b03c57563a4..e45ac3f926b1 100644 --- a/Documentation/devicetree/bindings/net/stmmac.txt +++ b/Documentation/devicetree/bindings/net/stmmac.txt @@ -39,6 +39,10 @@ Optional properties: further clocks may be specified in derived bindings. - clock-names: One name for each entry in the clocks property, the first one should be "stmmaceth". +- clk_ptp_ref: this is the PTP reference clock; in case of the PTP is + available this clock is used for programming the Timestamp Addend Register. + If not passed then the system clock will be used and this is fine on some + platforms. Examples: diff --git a/Documentation/devicetree/bindings/sound/rockchip-i2s.txt b/Documentation/devicetree/bindings/sound/rockchip-i2s.txt index 6c55fcfe5e1d..9b82c20b306b 100644 --- a/Documentation/devicetree/bindings/sound/rockchip-i2s.txt +++ b/Documentation/devicetree/bindings/sound/rockchip-i2s.txt @@ -31,7 +31,7 @@ i2s@ff890000 { #address-cells = <1>; #size-cells = <0>; dmas = <&pdma1 0>, <&pdma1 1>; - dma-names = "rx", "tx"; + dma-names = "tx", "rx"; clock-names = "i2s_hclk", "i2s_clk"; clocks = <&cru HCLK_I2S0>, <&cru SCLK_I2S0>; }; diff --git a/Documentation/devicetree/bindings/spi/spi-rockchip.txt b/Documentation/devicetree/bindings/spi/spi-rockchip.txt index 7bab35575817..467dec441c62 100644 --- a/Documentation/devicetree/bindings/spi/spi-rockchip.txt +++ b/Documentation/devicetree/bindings/spi/spi-rockchip.txt @@ -16,11 +16,15 @@ Required Properties: - clocks: Must contain an entry for each entry in clock-names. - clock-names: Shall be "spiclk" for the transfer-clock, and "apb_pclk" for the peripheral clock. +- #address-cells: should be 1. +- #size-cells: should be 0. + +Optional Properties: + - dmas: DMA specifiers for tx and rx dma. See the DMA client binding, Documentation/devicetree/bindings/dma/dma.txt - dma-names: DMA request names should include "tx" and "rx" if present. -- #address-cells: should be 1. -- #size-cells: should be 0. + Example: diff --git a/Documentation/devicetree/bindings/staging/imx-drm/ldb.txt b/Documentation/devicetree/bindings/staging/imx-drm/ldb.txt index 578a1fca366e..443bcb6134d5 100644 --- a/Documentation/devicetree/bindings/staging/imx-drm/ldb.txt +++ b/Documentation/devicetree/bindings/staging/imx-drm/ldb.txt @@ -56,6 +56,9 @@ Required properties: - fsl,data-width : should be <18> or <24> - port: A port node with endpoint definitions as defined in Documentation/devicetree/bindings/media/video-interfaces.txt. + On i.MX5, the internal two-input-multiplexer is used. + Due to hardware limitations, only one port (port@[0,1]) + can be used for each channel (lvds-channel@[0,1], respectively) On i.MX6, there should be four ports (port@[0-3]) that correspond to the four LVDS multiplexer inputs. @@ -78,6 +81,8 @@ ldb: ldb@53fa8008 { "di0", "di1"; lvds-channel@0 { + #address-cells = <1>; + #size-cells = <0>; reg = <0>; fsl,data-mapping = "spwg"; fsl,data-width = <24>; @@ -86,7 +91,9 @@ ldb: ldb@53fa8008 { /* ... */ }; - port { + port@0 { + reg = <0>; + lvds0_in: endpoint { remote-endpoint = <&ipu_di0_lvds0>; }; @@ -94,6 +101,8 @@ ldb: ldb@53fa8008 { }; lvds-channel@1 { + #address-cells = <1>; + #size-cells = <0>; reg = <1>; fsl,data-mapping = "spwg"; fsl,data-width = <24>; @@ -102,7 +111,9 @@ ldb: ldb@53fa8008 { /* ... */ }; - port { + port@1 { + reg = <1>; + lvds1_in: endpoint { remote-endpoint = <&ipu_di1_lvds1>; }; diff --git a/Documentation/devicetree/bindings/usb/mxs-phy.txt b/Documentation/devicetree/bindings/usb/mxs-phy.txt index cef181a9d8bd..96681c93b86d 100644 --- a/Documentation/devicetree/bindings/usb/mxs-phy.txt +++ b/Documentation/devicetree/bindings/usb/mxs-phy.txt @@ -5,6 +5,7 @@ Required properties: * "fsl,imx23-usbphy" for imx23 and imx28 * "fsl,imx6q-usbphy" for imx6dq and imx6dl * "fsl,imx6sl-usbphy" for imx6sl + * "fsl,imx6sx-usbphy" for imx6sx "fsl,imx23-usbphy" is still a fallback for other strings - reg: Should contain registers location and length - interrupts: Should contain phy interrupt diff --git a/Documentation/devicetree/bindings/video/analog-tv-connector.txt b/Documentation/devicetree/bindings/video/analog-tv-connector.txt index 0218fcdc1299..0c0970c210ab 100644 --- a/Documentation/devicetree/bindings/video/analog-tv-connector.txt +++ b/Documentation/devicetree/bindings/video/analog-tv-connector.txt @@ -2,7 +2,7 @@ Analog TV Connector =================== Required properties: -- compatible: "composite-connector" or "svideo-connector" +- compatible: "composite-video-connector" or "svideo-connector" Optional properties: - label: a symbolic name for the connector @@ -14,7 +14,7 @@ Example ------- tv: connector { - compatible = "composite-connector"; + compatible = "composite-video-connector"; label = "tv"; port { diff --git a/Documentation/devicetree/of_selftest.txt b/Documentation/devicetree/of_selftest.txt new file mode 100644 index 000000000000..3a2f54d07fc5 --- /dev/null +++ b/Documentation/devicetree/of_selftest.txt @@ -0,0 +1,211 @@ +Open Firmware Device Tree Selftest +---------------------------------- + +Author: Gaurav Minocha <gaurav.minocha.os@gmail.com> + +1. Introduction + +This document explains how the test data required for executing OF selftest +is attached to the live tree dynamically, independent of the machine's +architecture. + +It is recommended to read the following documents before moving ahead. + +[1] Documentation/devicetree/usage-model.txt +[2] http://www.devicetree.org/Device_Tree_Usage + +OF Selftest has been designed to test the interface (include/linux/of.h) +provided to device driver developers to fetch the device information..etc. +from the unflattened device tree data structure. This interface is used by +most of the device drivers in various use cases. + + +2. Test-data + +The Device Tree Source file (drivers/of/testcase-data/testcases.dts) contains +the test data required for executing the unit tests automated in +drivers/of/selftests.c. Currently, following Device Tree Source Include files +(.dtsi) are included in testcase.dts: + +drivers/of/testcase-data/tests-interrupts.dtsi +drivers/of/testcase-data/tests-platform.dtsi +drivers/of/testcase-data/tests-phandle.dtsi +drivers/of/testcase-data/tests-match.dtsi + +When the kernel is build with OF_SELFTEST enabled, then the following make rule + +$(obj)/%.dtb: $(src)/%.dts FORCE + $(call if_changed_dep, dtc) + +is used to compile the DT source file (testcase.dts) into a binary blob +(testcase.dtb), also referred as flattened DT. + +After that, using the following rule the binary blob above is wrapped as an +assembly file (testcase.dtb.S). + +$(obj)/%.dtb.S: $(obj)/%.dtb + $(call cmd, dt_S_dtb) + +The assembly file is compiled into an object file (testcase.dtb.o), and is +linked into the kernel image. + + +2.1. Adding the test data + +Un-flattened device tree structure: + +Un-flattened device tree consists of connected device_node(s) in form of a tree +structure described below. + +// following struct members are used to construct the tree +struct device_node { + ... + struct device_node *parent; + struct device_node *child; + struct device_node *sibling; + struct device_node *allnext; /* next in list of all nodes */ + ... + }; + +Figure 1, describes a generic structure of machine’s un-flattened device tree +considering only child and sibling pointers. There exists another pointer, +*parent, that is used to traverse the tree in the reverse direction. So, at +a particular level the child node and all the sibling nodes will have a parent +pointer pointing to a common node (e.g. child1, sibling2, sibling3, sibling4’s +parent points to root node) + +root (‘/’) + | +child1 -> sibling2 -> sibling3 -> sibling4 -> null + | | | | + | | | null + | | | + | | child31 -> sibling32 -> null + | | | | + | | null null + | | + | child21 -> sibling22 -> sibling23 -> null + | | | | + | null null null + | +child11 -> sibling12 -> sibling13 -> sibling14 -> null + | | | | + | | | null + | | | + null null child131 -> null + | + null + +Figure 1: Generic structure of un-flattened device tree + + +*allnext: it is used to link all the nodes of DT into a list. So, for the + above tree the list would be as follows: + +root->child1->child11->sibling12->sibling13->child131->sibling14->sibling2-> +child21->sibling22->sibling23->sibling3->child31->sibling32->sibling4->null + +Before executing OF selftest, it is required to attach the test data to +machine's device tree (if present). So, when selftest_data_add() is called, +at first it reads the flattened device tree data linked into the kernel image +via the following kernel symbols: + +__dtb_testcases_begin - address marking the start of test data blob +__dtb_testcases_end - address marking the end of test data blob + +Secondly, it calls of_fdt_unflatten_device_tree() to unflatten the flattened +blob. And finally, if the machine’s device tree (i.e live tree) is present, +then it attaches the unflattened test data tree to the live tree, else it +attaches itself as a live device tree. + +attach_node_and_children() uses of_attach_node() to attach the nodes into the +live tree as explained below. To explain the same, the test data tree described + in Figure 2 is attached to the live tree described in Figure 1. + +root (‘/’) + | + testcase-data + | + test-child0 -> test-sibling1 -> test-sibling2 -> test-sibling3 -> null + | | | | + test-child01 null null null + + +allnext list: + +root->testcase-data->test-child0->test-child01->test-sibling1->test-sibling2 +->test-sibling3->null + +Figure 2: Example test data tree to be attached to live tree. + +According to the scenario above, the live tree is already present so it isn’t +required to attach the root(‘/’) node. All other nodes are attached by calling +of_attach_node() on each node. + +In the function of_attach_node(), the new node is attached as the child of the +given parent in live tree. But, if parent already has a child then the new node +replaces the current child and turns it into its sibling. So, when the testcase +data node is attached to the live tree above (Figure 1), the final structure is + as shown in Figure 3. + +root (‘/’) + | +testcase-data -> child1 -> sibling2 -> sibling3 -> sibling4 -> null + | | | | | + (...) | | | null + | | child31 -> sibling32 -> null + | | | | + | | null null + | | + | child21 -> sibling22 -> sibling23 -> null + | | | | + | null null null + | + child11 -> sibling12 -> sibling13 -> sibling14 -> null + | | | | + null null | null + | + child131 -> null + | + null +----------------------------------------------------------------------- + +root (‘/’) + | +testcase-data -> child1 -> sibling2 -> sibling3 -> sibling4 -> null + | | | | | + | (...) (...) (...) null + | +test-sibling3 -> test-sibling2 -> test-sibling1 -> test-child0 -> null + | | | | + null null null test-child01 + + +Figure 3: Live device tree structure after attaching the testcase-data. + + +Astute readers would have noticed that test-child0 node becomes the last +sibling compared to the earlier structure (Figure 2). After attaching first +test-child0 the test-sibling1 is attached that pushes the child node +(i.e. test-child0) to become a sibling and makes itself a child node, + as mentioned above. + +If a duplicate node is found (i.e. if a node with same full_name property is +already present in the live tree), then the node isn’t attached rather its +properties are updated to the live tree’s node by calling the function +update_node_properties(). + + +2.2. Removing the test data + +Once the test case execution is complete, selftest_data_remove is called in +order to remove the device nodes attached initially (first the leaf nodes are +detached and then moving up the parent nodes are removed, and eventually the +whole tree). selftest_data_remove() calls detach_node_and_children() that uses +of_detach_node() to detach the nodes from the live device tree. + +To detach a node, of_detach_node() first updates all_next linked list, by +attaching the previous node’s allnext to current node’s allnext pointer. And +then, it either updates the child pointer of given node’s parent to its +sibling or attaches the previous sibling to the given node’s sibling, as +appropriate. That is it :) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 5ae8608ca9f5..ccbab5653bb8 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3303,11 +3303,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. tdfx= [HW,DRM] - test_suspend= [SUSPEND] + test_suspend= [SUSPEND][,N] Specify "mem" (for Suspend-to-RAM) or "standby" (for - standby suspend) as the system sleep state to briefly - enter during system startup. The system is woken from - this state using a wakeup-capable RTC alarm. + standby suspend) or "freeze" (for suspend type freeze) + as the system sleep state during system startup with + the optional capability to repeat N number of times. + The system is woken from this state using a + wakeup-capable RTC alarm. thash_entries= [KNL,NET] Set number of hash buckets for TCP connection @@ -3541,6 +3543,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted. bogus residue values); s = SINGLE_LUN (the device has only one Logical Unit); + u = IGNORE_UAS (don't bind to the uas driver); w = NO_WP_DETECT (don't test whether the medium is write-protected). Example: quirks=0419:aaf5:rl,0421:0433:rc diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt index c48a9704bda8..d16f424c5e8d 100644 --- a/Documentation/networking/filter.txt +++ b/Documentation/networking/filter.txt @@ -462,9 +462,9 @@ JIT compiler ------------ The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC, -ARM and s390 and can be enabled through CONFIG_BPF_JIT. The JIT compiler is -transparently invoked for each attached filter from user space or for internal -kernel users if it has been previously enabled by root: +ARM, MIPS and s390 and can be enabled through CONFIG_BPF_JIT. The JIT compiler +is transparently invoked for each attached filter from user space or for +internal kernel users if it has been previously enabled by root: echo 1 > /proc/sys/net/core/bpf_jit_enable diff --git a/Documentation/power/suspend-and-interrupts.txt b/Documentation/power/suspend-and-interrupts.txt new file mode 100644 index 000000000000..69663640dea5 --- /dev/null +++ b/Documentation/power/suspend-and-interrupts.txt @@ -0,0 +1,123 @@ +System Suspend and Device Interrupts + +Copyright (C) 2014 Intel Corp. +Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + + +Suspending and Resuming Device IRQs +----------------------------------- + +Device interrupt request lines (IRQs) are generally disabled during system +suspend after the "late" phase of suspending devices (that is, after all of the +->prepare, ->suspend and ->suspend_late callbacks have been executed for all +devices). That is done by suspend_device_irqs(). + +The rationale for doing so is that after the "late" phase of device suspend +there is no legitimate reason why any interrupts from suspended devices should +trigger and if any devices have not been suspended properly yet, it is better to +block interrupts from them anyway. Also, in the past we had problems with +interrupt handlers for shared IRQs that device drivers implementing them were +not prepared for interrupts triggering after their devices had been suspended. +In some cases they would attempt to access, for example, memory address spaces +of suspended devices and cause unpredictable behavior to ensue as a result. +Unfortunately, such problems are very difficult to debug and the introduction +of suspend_device_irqs(), along with the "noirq" phase of device suspend and +resume, was the only practical way to mitigate them. + +Device IRQs are re-enabled during system resume, right before the "early" phase +of resuming devices (that is, before starting to execute ->resume_early +callbacks for devices). The function doing that is resume_device_irqs(). + + +The IRQF_NO_SUSPEND Flag +------------------------ + +There are interrupts that can legitimately trigger during the entire system +suspend-resume cycle, including the "noirq" phases of suspending and resuming +devices as well as during the time when nonboot CPUs are taken offline and +brought back online. That applies to timer interrupts in the first place, +but also to IPIs and to some other special-purpose interrupts. + +The IRQF_NO_SUSPEND flag is used to indicate that to the IRQ subsystem when +requesting a special-purpose interrupt. It causes suspend_device_irqs() to +leave the corresponding IRQ enabled so as to allow the interrupt to work all +the time as expected. + +Note that the IRQF_NO_SUSPEND flag affects the entire IRQ and not just one +user of it. Thus, if the IRQ is shared, all of the interrupt handlers installed +for it will be executed as usual after suspend_device_irqs(), even if the +IRQF_NO_SUSPEND flag was not passed to request_irq() (or equivalent) by some of +the IRQ's users. For this reason, using IRQF_NO_SUSPEND and IRQF_SHARED at the +same time should be avoided. + + +System Wakeup Interrupts, enable_irq_wake() and disable_irq_wake() +------------------------------------------------------------------ + +System wakeup interrupts generally need to be configured to wake up the system +from sleep states, especially if they are used for different purposes (e.g. as +I/O interrupts) in the working state. + +That may involve turning on a special signal handling logic within the platform +(such as an SoC) so that signals from a given line are routed in a different way +during system sleep so as to trigger a system wakeup when needed. For example, +the platform may include a dedicated interrupt controller used specifically for +handling system wakeup events. Then, if a given interrupt line is supposed to +wake up the system from sleep sates, the corresponding input of that interrupt +controller needs to be enabled to receive signals from the line in question. +After wakeup, it generally is better to disable that input to prevent the +dedicated controller from triggering interrupts unnecessarily. + +The IRQ subsystem provides two helper functions to be used by device drivers for +those purposes. Namely, enable_irq_wake() turns on the platform's logic for +handling the given IRQ as a system wakeup interrupt line and disable_irq_wake() +turns that logic off. + +Calling enable_irq_wake() causes suspend_device_irqs() to treat the given IRQ +in a special way. Namely, the IRQ remains enabled, by on the first interrupt +it will be disabled, marked as pending and "suspended" so that it will be +re-enabled by resume_device_irqs() during the subsequent system resume. Also +the PM core is notified about the event which casues the system suspend in +progress to be aborted (that doesn't have to happen immediately, but at one +of the points where the suspend thread looks for pending wakeup events). + +This way every interrupt from a wakeup interrupt source will either cause the +system suspend currently in progress to be aborted or wake up the system if +already suspended. However, after suspend_device_irqs() interrupt handlers are +not executed for system wakeup IRQs. They are only executed for IRQF_NO_SUSPEND +IRQs at that time, but those IRQs should not be configured for system wakeup +using enable_irq_wake(). + + +Interrupts and Suspend-to-Idle +------------------------------ + +Suspend-to-idle (also known as the "freeze" sleep state) is a relatively new +system sleep state that works by idling all of the processors and waiting for +interrupts right after the "noirq" phase of suspending devices. + +Of course, this means that all of the interrupts with the IRQF_NO_SUSPEND flag +set will bring CPUs out of idle while in that state, but they will not cause the +IRQ subsystem to trigger a system wakeup. + +System wakeup interrupts, in turn, will trigger wakeup from suspend-to-idle in +analogy with what they do in the full system suspend case. The only difference +is that the wakeup from suspend-to-idle is signaled using the usual working +state interrupt delivery mechanisms and doesn't require the platform to use +any special interrupt handling logic for it to work. + + +IRQF_NO_SUSPEND and enable_irq_wake() +------------------------------------- + +There are no valid reasons to use both enable_irq_wake() and the IRQF_NO_SUSPEND +flag on the same IRQ. + +First of all, if the IRQ is not shared, the rules for handling IRQF_NO_SUSPEND +interrupts (interrupt handlers are invoked after suspend_device_irqs()) are +directly at odds with the rules for handling system wakeup interrupts (interrupt +handlers are not invoked after suspend_device_irqs()). + +Second, both enable_irq_wake() and IRQF_NO_SUSPEND apply to entire IRQs and not +to individual interrupt handlers, so sharing an IRQ between a system wakeup +interrupt source and an IRQF_NO_SUSPEND interrupt source does not make sense. |