aboutsummaryrefslogtreecommitdiff
path: root/Documentation/power/pm_qos_interface.rst
diff options
context:
space:
mode:
authorLibravatar Linus Torvalds <torvalds@linux-foundation.org>2023-02-21 18:24:12 -0800
committerLibravatar Linus Torvalds <torvalds@linux-foundation.org>2023-02-21 18:24:12 -0800
commit5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch)
treecc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/power/pm_qos_interface.rst
downloadlinux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz
linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski: "Core: - Add dedicated kmem_cache for typical/small skb->head, avoid having to access struct page at kfree time, and improve memory use. - Introduce sysctl to set default RPS configuration for new netdevs. - Define Netlink protocol specification format which can be used to describe messages used by each family and auto-generate parsers. Add tools for generating kernel data structures and uAPI headers. - Expose all net/core sysctls inside netns. - Remove 4s sleep in netpoll if carrier is instantly detected on boot. - Add configurable limit of MDB entries per port, and port-vlan. - Continue populating drop reasons throughout the stack. - Retire a handful of legacy Qdiscs and classifiers. Protocols: - Support IPv4 big TCP (TSO frames larger than 64kB). - Add IP_LOCAL_PORT_RANGE socket option, to control local port range on socket by socket basis. - Track and report in procfs number of MPTCP sockets used. - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path manager. - IPv6: don't check net.ipv6.route.max_size and rely on garbage collection to free memory (similarly to IPv4). - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986). - ICMP: add per-rate limit counters. - Add support for user scanning requests in ieee802154. - Remove static WEP support. - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate reporting. - WiFi 7 EHT channel puncturing support (client & AP). BPF: - Add a rbtree data structure following the "next-gen data structure" precedent set by recently added linked list, that is, by using kfunc + kptr instead of adding a new BPF map type. - Expose XDP hints via kfuncs with initial support for RX hash and timestamp metadata. - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to better support decap on GRE tunnel devices not operating in collect metadata. - Improve x86 JIT's codegen for PROBE_MEM runtime error checks. - Remove the need for trace_printk_lock for bpf_trace_printk and bpf_trace_vprintk helpers. - Extend libbpf's bpf_tracing.h support for tracing arguments of kprobes/uprobes and syscall as a special case. - Significantly reduce the search time for module symbols by livepatch and BPF. - Enable cpumasks to be used as kptrs, which is useful for tracing programs tracking which tasks end up running on which CPUs in different time intervals. - Add support for BPF trampoline on s390x and riscv64. - Add capability to export the XDP features supported by the NIC. - Add __bpf_kfunc tag for marking kernel functions as kfuncs. - Add cgroup.memory=nobpf kernel parameter option to disable BPF memory accounting for container environments. Netfilter: - Remove the CLUSTERIP target. It has been marked as obsolete for years, and we still have WARN splats wrt races of the out-of-band /proc interface installed by this target. - Add 'destroy' commands to nf_tables. They are identical to the existing 'delete' commands, but do not return an error if the referenced object (set, chain, rule...) did not exist. Driver API: - Improve cpumask_local_spread() locality to help NICs set the right IRQ affinity on AMD platforms. - Separate C22 and C45 MDIO bus transactions more clearly. - Introduce new DCB table to control DSCP rewrite on egress. - Support configuration of Physical Layer Collision Avoidance (PLCA) Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of shared medium Ethernet. - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing preemption of low priority frames by high priority frames. - Add support for controlling MACSec offload using netlink SET. - Rework devlink instance refcounts to allow registration and de-registration under the instance lock. Split the code into multiple files, drop some of the unnecessarily granular locks and factor out common parts of netlink operation handling. - Add TX frame aggregation parameters (for USB drivers). - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning messages with notifications for debug. - Allow offloading of UDP NEW connections via act_ct. - Add support for per action HW stats in TC. - Support hardware miss to TC action (continue processing in SW from a specific point in the action chain). - Warn if old Wireless Extension user space interface is used with modern cfg80211/mac80211 drivers. Do not support Wireless Extensions for Wi-Fi 7 devices at all. Everyone should switch to using nl80211 interface instead. - Improve the CAN bit timing configuration. Use extack to return error messages directly to user space, update the SJW handling, including the definition of a new default value that will benefit CAN-FD controllers, by increasing their oscillator tolerance. New hardware / drivers: - Ethernet: - nVidia BlueField-3 support (control traffic driver) - Ethernet support for imx93 SoCs - Motorcomm yt8531 gigabit Ethernet PHY - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA) - Microchip LAN8841 PHY (incl. cable diagnostics and PTP) - Amlogic gxl MDIO mux - WiFi: - RealTek RTL8188EU (rtl8xxxu) - Qualcomm Wi-Fi 7 devices (ath12k) - CAN: - Renesas R-Car V4H Drivers: - Bluetooth: - Set Per Platform Antenna Gain (PPAG) for Intel controllers. - Ethernet NICs: - Intel (1G, igc): - support TSN / Qbv / packet scheduling features of i226 model - Intel (100G, ice): - use GNSS subsystem instead of TTY - multi-buffer XDP support - extend support for GPIO pins to E823 devices - nVidia/Mellanox: - update the shared buffer configuration on PFC commands - implement PTP adjphase function for HW offset control - TC support for Geneve and GRE with VF tunnel offload - more efficient crypto key management method - multi-port eswitch support - Netronome/Corigine: - add DCB IEEE support - support IPsec offloading for NFP3800 - Freescale/NXP (enetc): - support XDP_REDIRECT for XDP non-linear buffers - improve reconfig, avoid link flap and waiting for idle - support MAC Merge layer - Other NICs: - sfc/ef100: add basic devlink support for ef100 - ionic: rx_push mode operation (writing descriptors via MMIO) - bnxt: use the auxiliary bus abstraction for RDMA - r8169: disable ASPM and reset bus in case of tx timeout - cpsw: support QSGMII mode for J721e CPSW9G - cpts: support pulse-per-second output - ngbe: add an mdio bus driver - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing - r8152: handle devices with FW with NCM support - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation - virtio-net: support multi buffer XDP - virtio/vsock: replace virtio_vsock_pkt with sk_buff - tsnep: XDP support - Ethernet high-speed switches: - nVidia/Mellanox (mlxsw): - add support for latency TLV (in FW control messages) - Microchip (sparx5): - separate explicit and implicit traffic forwarding rules, make the implicit rules always active - add support for egress DSCP rewrite - IS0 VCAP support (Ingress Classification) - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS etc.) - ES2 VCAP support (Egress Access Control) - support for Per-Stream Filtering and Policing (802.1Q, 8.6.5.1) - Ethernet embedded switches: - Marvell (mv88e6xxx): - add MAB (port auth) offload support - enable PTP receive for mv88e6390 - NXP (ocelot): - support MAC Merge layer - support for the the vsc7512 internal copper phys - Microchip: - lan9303: convert to PHYLINK - lan966x: support TC flower filter statistics - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x - lan937x: support Credit Based Shaper configuration - ksz9477: support Energy Efficient Ethernet - other: - qca8k: convert to regmap read/write API, use bulk operations - rswitch: Improve TX timestamp accuracy - Intel WiFi (iwlwifi): - EHT (Wi-Fi 7) rate reporting - STEP equalizer support: transfer some STEP (connection to radio on platforms with integrated wifi) related parameters from the BIOS to the firmware. - Qualcomm 802.11ax WiFi (ath11k): - IPQ5018 support - Fine Timing Measurement (FTM) responder role support - channel 177 support - MediaTek WiFi (mt76): - per-PHY LED support - mt7996: EHT (Wi-Fi 7) support - Wireless Ethernet Dispatch (WED) reset support - switch to using page pool allocator - RealTek WiFi (rtw89): - support new version of Bluetooth co-existance - Mobile: - rmnet: support TX aggregation" * tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits) page_pool: add a comment explaining the fragment counter usage net: ethtool: fix __ethtool_dev_mm_supported() implementation ethtool: pse-pd: Fix double word in comments xsk: add linux/vmalloc.h to xsk.c sefltests: netdevsim: wait for devlink instance after netns removal selftest: fib_tests: Always cleanup before exit net/mlx5e: Align IPsec ASO result memory to be as required by hardware net/mlx5e: TC, Set CT miss to the specific ct action instance net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG net/mlx5: Refactor tc miss handling to a single function net/mlx5: Kconfig: Make tc offload depend on tc skb extension net/sched: flower: Support hardware miss to tc action net/sched: flower: Move filter handle initialization earlier net/sched: cls_api: Support hardware miss to tc action net/sched: Rename user cookie and act cookie sfc: fix builds without CONFIG_RTC_LIB sfc: clean up some inconsistent indentings net/mlx4_en: Introduce flexible array to silence overflow warning net: lan966x: Fix possible deadlock inside PTP net/ulp: Remove redundant ->clone() test in inet_clone_ulp(). ...
Diffstat (limited to 'Documentation/power/pm_qos_interface.rst')
-rw-r--r--Documentation/power/pm_qos_interface.rst218
1 files changed, 218 insertions, 0 deletions
diff --git a/Documentation/power/pm_qos_interface.rst b/Documentation/power/pm_qos_interface.rst
new file mode 100644
index 000000000..69b0fe3e2
--- /dev/null
+++ b/Documentation/power/pm_qos_interface.rst
@@ -0,0 +1,218 @@
+===============================
+PM Quality Of Service Interface
+===============================
+
+This interface provides a kernel and user mode interface for registering
+performance expectations by drivers, subsystems and user space applications on
+one of the parameters.
+
+Two different PM QoS frameworks are available:
+ * CPU latency QoS.
+ * The per-device PM QoS framework provides the API to manage the
+ per-device latency constraints and PM QoS flags.
+
+The latency unit used in the PM QoS framework is the microsecond (usec).
+
+
+1. PM QoS framework
+===================
+
+A global list of CPU latency QoS requests is maintained along with an aggregated
+(effective) target value. The aggregated target value is updated with changes
+to the request list or elements of the list. For CPU latency QoS, the
+aggregated target value is simply the min of the request values held in the list
+elements.
+
+Note: the aggregated target value is implemented as an atomic variable so that
+reading the aggregated value does not require any locking mechanism.
+
+From kernel space the use of this interface is simple:
+
+void cpu_latency_qos_add_request(handle, target_value):
+ Will insert an element into the CPU latency QoS list with the target value.
+ Upon change to this list the new target is recomputed and any registered
+ notifiers are called only if the target value is now different.
+ Clients of PM QoS need to save the returned handle for future use in other
+ PM QoS API functions.
+
+void cpu_latency_qos_update_request(handle, new_target_value):
+ Will update the list element pointed to by the handle with the new target
+ value and recompute the new aggregated target, calling the notification tree
+ if the target is changed.
+
+void cpu_latency_qos_remove_request(handle):
+ Will remove the element. After removal it will update the aggregate target
+ and call the notification tree if the target was changed as a result of
+ removing the request.
+
+int cpu_latency_qos_limit():
+ Returns the aggregated value for the CPU latency QoS.
+
+int cpu_latency_qos_request_active(handle):
+ Returns if the request is still active, i.e. it has not been removed from the
+ CPU latency QoS list.
+
+int cpu_latency_qos_add_notifier(notifier):
+ Adds a notification callback function to the CPU latency QoS. The callback is
+ called when the aggregated value for the CPU latency QoS is changed.
+
+int cpu_latency_qos_remove_notifier(notifier):
+ Removes the notification callback function from the CPU latency QoS.
+
+
+From user space:
+
+The infrastructure exposes one device node, /dev/cpu_dma_latency, for the CPU
+latency QoS.
+
+Only processes can register a PM QoS request. To provide for automatic
+cleanup of a process, the interface requires the process to register its
+parameter requests as follows.
+
+To register the default PM QoS target for the CPU latency QoS, the process must
+open /dev/cpu_dma_latency.
+
+As long as the device node is held open that process has a registered
+request on the parameter.
+
+To change the requested target value, the process needs to write an s32 value to
+the open device node. Alternatively, it can write a hex string for the value
+using the 10 char long format e.g. "0x12345678". This translates to a
+cpu_latency_qos_update_request() call.
+
+To remove the user mode request for a target value simply close the device
+node.
+
+
+2. PM QoS per-device latency and flags framework
+================================================
+
+For each device, there are three lists of PM QoS requests. Two of them are
+maintained along with the aggregated targets of resume latency and active
+state latency tolerance (in microseconds) and the third one is for PM QoS flags.
+Values are updated in response to changes of the request list.
+
+The target values of resume latency and active state latency tolerance are
+simply the minimum of the request values held in the parameter list elements.
+The PM QoS flags aggregate value is a gather (bitwise OR) of all list elements'
+values. One device PM QoS flag is defined currently: PM_QOS_FLAG_NO_POWER_OFF.
+
+Note: The aggregated target values are implemented in such a way that reading
+the aggregated value does not require any locking mechanism.
+
+
+From kernel mode the use of this interface is the following:
+
+int dev_pm_qos_add_request(device, handle, type, value):
+ Will insert an element into the list for that identified device with the
+ target value. Upon change to this list the new target is recomputed and any
+ registered notifiers are called only if the target value is now different.
+ Clients of dev_pm_qos need to save the handle for future use in other
+ dev_pm_qos API functions.
+
+int dev_pm_qos_update_request(handle, new_value):
+ Will update the list element pointed to by the handle with the new target
+ value and recompute the new aggregated target, calling the notification
+ trees if the target is changed.
+
+int dev_pm_qos_remove_request(handle):
+ Will remove the element. After removal it will update the aggregate target
+ and call the notification trees if the target was changed as a result of
+ removing the request.
+
+s32 dev_pm_qos_read_value(device, type):
+ Returns the aggregated value for a given device's constraints list.
+
+enum pm_qos_flags_status dev_pm_qos_flags(device, mask)
+ Check PM QoS flags of the given device against the given mask of flags.
+ The meaning of the return values is as follows:
+
+ PM_QOS_FLAGS_ALL:
+ All flags from the mask are set
+ PM_QOS_FLAGS_SOME:
+ Some flags from the mask are set
+ PM_QOS_FLAGS_NONE:
+ No flags from the mask are set
+ PM_QOS_FLAGS_UNDEFINED:
+ The device's PM QoS structure has not been initialized
+ or the list of requests is empty.
+
+int dev_pm_qos_add_ancestor_request(dev, handle, type, value)
+ Add a PM QoS request for the first direct ancestor of the given device whose
+ power.ignore_children flag is unset (for DEV_PM_QOS_RESUME_LATENCY requests)
+ or whose power.set_latency_tolerance callback pointer is not NULL (for
+ DEV_PM_QOS_LATENCY_TOLERANCE requests).
+
+int dev_pm_qos_expose_latency_limit(device, value)
+ Add a request to the device's PM QoS list of resume latency constraints and
+ create a sysfs attribute pm_qos_resume_latency_us under the device's power
+ directory allowing user space to manipulate that request.
+
+void dev_pm_qos_hide_latency_limit(device)
+ Drop the request added by dev_pm_qos_expose_latency_limit() from the device's
+ PM QoS list of resume latency constraints and remove sysfs attribute
+ pm_qos_resume_latency_us from the device's power directory.
+
+int dev_pm_qos_expose_flags(device, value)
+ Add a request to the device's PM QoS list of flags and create sysfs attribute
+ pm_qos_no_power_off under the device's power directory allowing user space to
+ change the value of the PM_QOS_FLAG_NO_POWER_OFF flag.
+
+void dev_pm_qos_hide_flags(device)
+ Drop the request added by dev_pm_qos_expose_flags() from the device's PM QoS
+ list of flags and remove sysfs attribute pm_qos_no_power_off from the device's
+ power directory.
+
+Notification mechanisms:
+
+The per-device PM QoS framework has a per-device notification tree.
+
+int dev_pm_qos_add_notifier(device, notifier, type):
+ Adds a notification callback function for the device for a particular request
+ type.
+
+ The callback is called when the aggregated value of the device constraints
+ list is changed.
+
+int dev_pm_qos_remove_notifier(device, notifier, type):
+ Removes the notification callback function for the device.
+
+
+Active state latency tolerance
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This device PM QoS type is used to support systems in which hardware may switch
+to energy-saving operation modes on the fly. In those systems, if the operation
+mode chosen by the hardware attempts to save energy in an overly aggressive way,
+it may cause excess latencies to be visible to software, causing it to miss
+certain protocol requirements or target frame or sample rates etc.
+
+If there is a latency tolerance control mechanism for a given device available
+to software, the .set_latency_tolerance callback in that device's dev_pm_info
+structure should be populated. The routine pointed to by it is should implement
+whatever is necessary to transfer the effective requirement value to the
+hardware.
+
+Whenever the effective latency tolerance changes for the device, its
+.set_latency_tolerance() callback will be executed and the effective value will
+be passed to it. If that value is negative, which means that the list of
+latency tolerance requirements for the device is empty, the callback is expected
+to switch the underlying hardware latency tolerance control mechanism to an
+autonomous mode if available. If that value is PM_QOS_LATENCY_ANY, in turn, and
+the hardware supports a special "no requirement" setting, the callback is
+expected to use it. That allows software to prevent the hardware from
+automatically updating the device's latency tolerance in response to its power
+state changes (e.g. during transitions from D3cold to D0), which generally may
+be done in the autonomous latency tolerance control mode.
+
+If .set_latency_tolerance() is present for the device, sysfs attribute
+pm_qos_latency_tolerance_us will be present in the devivce's power directory.
+Then, user space can use that attribute to specify its latency tolerance
+requirement for the device, if any. Writing "any" to it means "no requirement,
+but do not let the hardware control latency tolerance" and writing "auto" to it
+allows the hardware to be switched to the autonomous mode if there are no other
+requirements from the kernel side in the device's list.
+
+Kernel code can use the functions described above along with the
+DEV_PM_QOS_LATENCY_TOLERANCE device PM QoS type to add, remove and update
+latency tolerance requirements for devices.