linux/drivers
Arnd Bergmann f46f11dc1e ARM SCMI support for v4.17
ARM System Control and Management Interface(SCMI)[1] is more flexible and
 easily extensible than any of the existing interfaces.
 
 Few existing as well as future ARM platforms provide micro-controllers
 to abstract various power and other system management tasks which have
 similar interfaces, both in terms of the functions that are provided by
 them, and in terms of how requests are communicated to them.
 
 There are quite a few protocols like ARM SCPI, TI SCI, QCOM RPM, Nvidia Tegra
 BPMP, and so on already. This specification is to standardize and avoid any
 further fragmentation in the design of such interface by various vendors.
 
 The current SCMI driver implementation is very basic and initial support.
 It lacks support for notifications, asynchronous/delayed response, perf/power
 statistics region and sensor register region.
 
 Mailbox is the only form of transport supported currently in the driver.
 SCMI supports interrupt based mailbox communication, where, on completion
 of the processing of a message, the caller receives an interrupt as well as
 polling for completion.
 
 SCMI is designed to minimize the dependency on the mailbox/transport
 hardware. So in terms of SCMI, each channel in the mailbox includes
 memory area, doorbell and completion interrupt.
 
 However the doorbell and completion interrupt is highly mailbox dependent
 which was bit of controversial as part of SCMI/mailbox discussions.
 
 Arnd and me discussed about the few aspects of SCMI and the mailbox framework:
 
 1. Use of mailbox framework for doorbell type mailbox controller:
    - Such hardware may not require any data to be sent to signal the remote
      about the presence of a message. The channel will have in-built
      information on how to trigger the signal to the remote.
      There are few mailbox controller drivers which are purely doorbell based.
      e.g.QCOM IPC, STM, Tegra, ACPI PCC,..etc
 
 2. Supporting other mailbox controller:
    - SCMI just needs a mechanism to signal the remote firmware. Such
      controller may need fixed message to be sent to trigger a doorbell.
      In such case we may need to get that data from DT and pass the same
      to the controller. It's not covered in the current DT binding, but
      can be extended as optional property in future.
 
      However handling notifications may be interesting on such mailbox, but
      again there is no way to interpret what the data field(remote message)
      means, it could be a bit mask or a number or don't-care.
 
 Arnd mentioned that he doesn't like the way the mailbox binding deals
 with doorbell-type hardware, but we do have quite a few precedent drivers
 already and changing the binding to add a data field would not make it any
 better, but could cause other problems. So he is happy with the status quo
 of SCMI implementation.
 
 [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0056a/index.html
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Merge tag 'scmi-updates-4.17' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into next/drivers

Pull "ARM SCMI support for v4.17" from Sudeep Holla:

ARM System Control and Management Interface(SCMI)[1] is more flexible and
easily extensible than any of the existing interfaces.

Few existing as well as future ARM platforms provide micro-controllers
to abstract various power and other system management tasks which have
similar interfaces, both in terms of the functions that are provided by
them, and in terms of how requests are communicated to them.

There are quite a few protocols like ARM SCPI, TI SCI, QCOM RPM, Nvidia Tegra
BPMP, and so on already. This specification is to standardize and avoid any
further fragmentation in the design of such interface by various vendors.

The current SCMI driver implementation is very basic and initial support.
It lacks support for notifications, asynchronous/delayed response, perf/power
statistics region and sensor register region.

Mailbox is the only form of transport supported currently in the driver.
SCMI supports interrupt based mailbox communication, where, on completion
of the processing of a message, the caller receives an interrupt as well as
polling for completion.

SCMI is designed to minimize the dependency on the mailbox/transport
hardware. So in terms of SCMI, each channel in the mailbox includes
memory area, doorbell and completion interrupt.

However the doorbell and completion interrupt is highly mailbox dependent
which was bit of controversial as part of SCMI/mailbox discussions.

Arnd and me discussed about the few aspects of SCMI and the mailbox framework:

1. Use of mailbox framework for doorbell type mailbox controller:
   - Such hardware may not require any data to be sent to signal the remote
     about the presence of a message. The channel will have in-built
     information on how to trigger the signal to the remote.
     There are few mailbox controller drivers which are purely doorbell based.
     e.g.QCOM IPC, STM, Tegra, ACPI PCC,..etc

2. Supporting other mailbox controller:
   - SCMI just needs a mechanism to signal the remote firmware. Such
     controller may need fixed message to be sent to trigger a doorbell.
     In such case we may need to get that data from DT and pass the same
     to the controller. It's not covered in the current DT binding, but
     can be extended as optional property in future.

     However handling notifications may be interesting on such mailbox, but
     again there is no way to interpret what the data field(remote message)
     means, it could be a bit mask or a number or don't-care.

Arnd mentioned that he doesn't like the way the mailbox binding deals
with doorbell-type hardware, but we do have quite a few precedent drivers
already and changing the binding to add a data field would not make it any
better, but could cause other problems. So he is happy with the status quo
of SCMI implementation.

[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0056a/index.html

* tag 'scmi-updates-4.17' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  cpufreq: scmi: add support for fast frequency switching
  cpufreq: add support for CPU DVFS based on SCMI message protocol
  hwmon: add support for sensors exported via ARM SCMI
  hwmon: (core) Add hwmon_max to hwmon_sensor_types enumeration
  clk: add support for clocks provided by SCMI
  firmware: arm_scmi: add device power domain support using genpd
  firmware: arm_scmi: add per-protocol channels support using idr objects
  firmware: arm_scmi: refactor in preparation to support per-protocol channels
  firmware: arm_scmi: add option for polling based performance domain operations
  firmware: arm_scmi: add support for polling based SCMI transfers
  firmware: arm_scmi: probe and initialise all the supported protocols
  firmware: arm_scmi: add initial support for sensor protocol
  firmware: arm_scmi: add initial support for power protocol
  firmware: arm_scmi: add initial support for clock protocol
  firmware: arm_scmi: add initial support for performance protocol
  firmware: arm_scmi: add scmi protocol bus to enumerate protocol devices
  firmware: arm_scmi: add common infrastructure and support for base protocol
  firmware: arm_scmi: add basic driver infrastructure for SCMI
  dt-bindings: arm: add support for ARM System Control and Management Interface(SCMI) protocol
  dt-bindings: mailbox: add support for mailbox client shared memory
2018-03-07 16:45:07 +01:00
..
accessibility
acpi Merge branches 'acpi-ec', 'acpi-tables' and 'acpi-doc' 2018-02-15 12:02:42 +01:00
amba
android ANDROID: binder: synchronize_rcu() when using POLLFREE. 2018-02-16 11:16:38 +01:00
ata pci-v4.16-changes 2018-02-06 09:59:40 -08:00
atm atm: he: use 64-bit arithmetic instead of 32-bit 2018-02-08 15:05:16 -05:00
auxdisplay
base ACPI updates for v4.16-rc2 2018-02-15 14:50:32 -08:00
bcma Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-01-19 22:59:33 -05:00
block block: fix a typo 2018-03-01 08:41:27 -07:00
bluetooth vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
bus perf/arm-cci: Untangle global cci_ctrl_base 2018-03-06 17:27:25 +01:00
cdrom
char tpm: fix potential buffer overruns caused by bit glitches on the bus 2018-02-26 15:43:46 -08:00
clk clk: add support for clocks provided by SCMI 2018-02-28 16:37:57 +00:00
clocksource clocksource/drivers/arc_timer: Update some comments 2018-02-28 13:55:14 +01:00
connector
cpufreq ARM SCMI support for v4.17 2018-03-07 16:45:07 +01:00
cpuidle powerpc updates for 4.16 2018-02-02 10:01:04 -08:00
crypto s390: 2018-02-26 09:28:35 -08:00
dax dax: ->direct_access does not sleep anymore 2018-02-26 12:32:29 -08:00
dca
devfreq
dio
dma Merge branch 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm 2018-02-02 09:50:51 -08:00
dma-buf vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
edac EDAC, sb_edac: Fix out of bound writes during DIMM configuration on KNL 2018-02-23 12:05:37 +01:00
eisa EISA: Delete error message for a failed memory allocation in eisa_probe() 2018-01-23 09:04:10 +01:00
extcon extcon: int3496: process id-pin first so that we start with the right status 2018-02-14 06:37:33 +09:00
firewire vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
firmware ARM SCMI support for v4.17 2018-03-07 16:45:07 +01:00
fmc
fpga
fsi
gpio gpio: Handle deferred probing in of_find_gpio() properly 2018-02-27 09:48:07 +01:00
gpu Merge branch 'drm-fixes-4.16' of git://people.freedesktop.org/~agd5f/linux into drm-fixes 2018-03-01 14:03:14 +10:00
hid usb: ldusb: add PIDs for new CASSY devices supported by this driver 2018-02-15 18:44:03 +01:00
hsi vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
hv vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
hwmon ARM SCMI support for v4.17 2018-03-07 16:45:07 +01:00
hwspinlock
hwtracing Char/Misc driver patches for 4.16-rc1 2018-02-01 10:31:17 -08:00
i2c i2c: octeon: Prevent error message on bus error 2018-03-02 11:11:15 +01:00
ide genhd: Rename get_disk() to get_disk_and_module() 2018-02-26 09:48:42 -07:00
idle
iio First round of IIO fixes for the 4.16 cycle. 2018-02-20 10:03:22 +01:00
infiniband RDMA/uverbs: Fix kernel panic while using XRC_TGT QP type 2018-02-21 13:52:19 -05:00
input vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
iommu treewide/trivial: Remove ';;$' typo noise 2018-02-22 10:59:33 +01:00
ipack
irqchip irqchip/bcm: Remove hashed address printing 2018-02-16 14:22:16 +00:00
isdn vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
leds vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
lightnvm
macintosh powerpc/macio: set a proper dma_coherent_mask 2018-02-13 08:58:53 -08:00
mailbox vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
mcb
md for-linus-20180302 2018-03-02 09:35:36 -08:00
media media: vb2: Makefile: place vb2-trace together with vb2-core 2018-02-26 11:39:04 -05:00
memory memory: brcmstb: dpfe: support new way of passing data from the DCPU 2018-02-23 10:56:59 -08:00
memstick
message scsi: mptfusion: Add bounds check in mptctl_hp_targetinfo() 2018-01-30 21:32:06 -05:00
mfd vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
misc powerpc fixes for 4.16 #4 2018-02-24 16:05:50 -08:00
mmc mmc: core: Avoid hanging to claim host for mmc via some nested calls 2018-02-27 15:12:37 +01:00
mtd mtd: nand: MTD_NAND_MARVELL should depend on HAS_DMA 2018-02-12 10:57:20 +01:00
mux Char/Misc driver patches for 4.16-rc1 2018-02-01 10:31:17 -08:00
net xen: fixes for v4.16-rc4 2018-03-02 10:19:57 -08:00
nfc
ntb NTB: ntb_perf: fix cast to restricted __le32 2018-01-28 22:17:24 -05:00
nubus
nvdimm libnvdimm: re-enable deep flush for pmem devices via fsync() 2018-03-02 19:31:40 -08:00
nvme Merge branch 'for-jens' of git://git.infradead.org/nvme into for-linus 2018-02-28 12:18:58 -07:00
nvmem
of device property: Constify device_get_match_data() 2018-02-12 10:41:11 +01:00
opp opp: cpu: Replace GFP_ATOMIC with GFP_KERNEL in dev_pm_opp_init_cpufreq_table 2018-02-12 15:07:46 +05:30
oprofile
parisc
parport
pci pci-v4.16-fixes-2 2018-03-02 17:44:39 -08:00
pcmcia Merge branch 'pcmcia' of git://git.kernel.org/pub/scm/linux/kernel/git/brodo/pcmcia 2018-02-08 11:48:49 -08:00
perf perf/arm-cci: Untangle global cci_ctrl_base 2018-03-06 17:27:25 +01:00
phy USB/PHY updates for 4.16-rc1 2018-02-01 09:40:49 -08:00
pinctrl pinctrl: meson-axg: adjust uart_ao_b pin group naming 2018-02-12 10:47:36 +01:00
platform platform/x86: wmi: Fix misuse of vsprintf extension %pULL 2018-03-01 10:01:39 -08:00
pnp
power power supply and reset changes for the v4.16 series 2018-01-31 12:55:31 -08:00
powercap
pps vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
ps3
ptp vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
pwm
rapidio vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
ras mm/memory_failure: Remove unused trapno from memory_failure 2018-01-23 12:17:42 -06:00
regulator regulator: Fix suspend to idle 2018-01-30 12:25:59 +00:00
remoteproc remoteproc updates for v4.16 2018-02-05 10:07:40 -08:00
reset reset: simple: Enable for ASPEED systems 2018-02-20 17:42:29 +01:00
rpmsg vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
rtc vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
s390 virtio: bugfixes 2018-02-15 14:29:27 -08:00
sbus pci-v4.16-changes 2018-02-06 09:59:40 -08:00
scsi SCSI fixes on 20180222 2018-02-23 14:09:43 -08:00
sfi
sh cpufreq: Add and use cpufreq_for_each_{valid_,}entry_idx() 2018-02-08 10:21:39 +01:00
siox
slimbus
sn
soc ARM: SoC fixes for 4.16 2018-02-28 16:11:04 -08:00
soundwire soundwire: Fix a signedness bug 2018-01-22 16:45:26 +01:00
spi Merge remote-tracking branch 'spi/topic/xilinx' into spi-next 2018-01-26 17:57:34 +00:00
spmi
ssb Merge git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers.git 2018-02-01 10:37:39 +02:00
staging Staging/IIO fixes for 4.16-rc2 2018-02-22 12:05:43 -08:00
target Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2018-02-09 14:49:46 -08:00
tc
tee
thermal Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux 2018-02-06 15:04:58 -08:00
thunderbolt
tty vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
uio vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
usb USB fixes for 4.16-rc3 2018-02-22 12:13:01 -08:00
uwb
vfio vfio: disable filesystem-dax page pinning 2018-03-02 18:00:04 -08:00
vhost vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
video Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-02-14 17:02:15 -08:00
virt vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
virtio virtio_pci: don't kfree device on register failure 2018-02-01 16:26:45 +02:00
visorbus
vlynq
vme
w1 Documentation updates for 4.16. New stuff includes refcount_t 2018-01-31 19:25:25 -08:00
watchdog watchdog: sp5100_tco.c: fix potential build failure 2018-02-19 17:44:05 +01:00
xen xen: fixes for v4.16-rc4 2018-03-02 10:19:57 -08:00
zorro
Kconfig Char/Misc driver patches for 4.16-rc1 2018-02-01 10:31:17 -08:00
Makefile pci-v4.16-changes 2018-02-06 09:59:40 -08:00