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authorArnd Bergmann <arnd@arndb.de>2018-03-07 16:45:07 +0100
committerArnd Bergmann <arnd@arndb.de>2018-03-07 16:45:07 +0100
commitf46f11dc1e86270935041fbc3920ba71a050a5fd (patch)
treee049f00eb27f573e2f3d90d379554c869f6469c3 /drivers/memory
parent819d38e95f8ac3fb2e26e42e5c3f19d95a07c847 (diff)
parent02f208c5c60549039445402505dea284e15f0f4f (diff)
downloadlinux-f46f11dc1e86270935041fbc3920ba71a050a5fd.tar.bz2
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
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