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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-19 10:09:22 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-19 10:09:22 -0700 |
| commit | f4cdf7ca9a1fdcca413157df19753f388a5a224e (patch) | |
| tree | 60a31895b2446cd7fa27514e8c2843534a0de0da /Documentation/driver-api/slimbus.rst | |
| download | linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.tar.gz linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.zip | |
Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-mediagrafted
Pull media updates from Mauro Carvalho Chehab:
- v4l2-core: added ISP statistics support and per-block validation
- v4l2-core: Allow unknown HDR10 white point and luminance
- New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor
- New codec: Milos: VPU v2.0 codec support
- isp driver: gained support for Dreamchip RPPX1 ISP framework
- vsp1 driver: gained support for RZ/T2H and RZ/N2H
- Novalake driver: gained CVS support for new NVL hardware
- dvb-core: fix feed leak on failed DMX_ADD_PID
- several driver fixes, cleanups and minor improvements
* tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits)
media: ipu-bridge: check all DMI entries when overriding sensor rotation
media: v4l2-async: avoid deleting unlinked ASC entry on link error
media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement
media: intel/ipu6: fix async notifier cleanup leak on parse error
media: staging/ipu7: fix async notifier UAF on probe error path
media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path
media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem()
media: rcar-isp: Fix VSPX reference leaks
media: rcar-isp: Release ISPCORE resources
media: i2c: imx415: Release runtime PM reference on VBLANK error
media: i2c: imx415: Return test pattern write errors
media: renesas: vsp1: Declare index variables in for loop statement
media: renesas: vsp1: Make reset control optional to support platforms without a reset line
media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs
media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs
media: nxp: imx8-isi: Add additional 32-bit RGB format support
media: nxp: imx8-isi: Add 16-bit raw Bayer format support
media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams
media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks
media: nxp: imx8-isi: Correct color map between V4L2 and ISI
...
Diffstat (limited to 'Documentation/driver-api/slimbus.rst')
| -rw-r--r-- | Documentation/driver-api/slimbus.rst | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/Documentation/driver-api/slimbus.rst b/Documentation/driver-api/slimbus.rst new file mode 100644 index 000000000..410eec79b --- /dev/null +++ b/Documentation/driver-api/slimbus.rst @@ -0,0 +1,132 @@ +============================ +Linux kernel SLIMbus support +============================ + +Overview +======== + +What is SLIMbus? +---------------- +SLIMbus (Serial Low Power Interchip Media Bus) is a specification developed by +MIPI (Mobile Industry Processor Interface) alliance. The bus uses master/slave +configuration, and is a 2-wire multi-drop implementation (clock, and data). + +Currently, SLIMbus is used to interface between application processors of SoCs +(System-on-Chip) and peripheral components (typically codec). SLIMbus uses +Time-Division-Multiplexing to accommodate multiple data channels, and +a control channel. + +The control channel is used for various control functions such as bus +management, configuration and status updates. These messages can be unicast (e.g. +reading/writing device specific values), or multicast (e.g. data channel +reconfiguration sequence is a broadcast message announced to all devices) + +A data channel is used for data-transfer between 2 SLIMbus devices. Data +channel uses dedicated ports on the device. + +Hardware description: +--------------------- +SLIMbus specification has different types of device classifications based on +their capabilities. +A manager device is responsible for enumeration, configuration, and dynamic +channel allocation. Every bus has 1 active manager. + +A generic device is a device providing application functionality (e.g. codec). + +Framer device is responsible for clocking the bus, and transmitting frame-sync +and framing information on the bus. + +Each SLIMbus component has an interface device for monitoring physical layer. + +Typically each SoC contains SLIMbus component having 1 manager, 1 framer device, +1 generic device (for data channel support), and 1 interface device. +External peripheral SLIMbus component usually has 1 generic device (for +functionality/data channel support), and an associated interface device. +The generic device's registers are mapped as 'value elements' so that they can +be written/read using SLIMbus control channel exchanging control/status type of +information. +In case there are multiple framer devices on the same bus, manager device is +responsible to select the active-framer for clocking the bus. + +Per specification, SLIMbus uses "clock gears" to do power management based on +current frequency and bandwidth requirements. There are 10 clock gears and each +gear changes the SLIMbus frequency to be twice its previous gear. + +Each device has a 6-byte enumeration-address and the manager assigns every +device with a 1-byte logical address after the devices report presence on the +bus. + +Software description: +--------------------- +There are 2 types of SLIMbus drivers: + +slim_controller represents a 'controller' for SLIMbus. This driver should +implement duties needed by the SoC (manager device, associated +interface device for monitoring the layers and reporting errors, default +framer device). + +slim_device represents the 'generic device/component' for SLIMbus, and a +slim_driver should implement driver for that slim_device. + +Device notifications to the driver: +----------------------------------- +Since SLIMbus devices have mechanisms for reporting their presence, the +framework allows drivers to bind when corresponding devices report their +presence on the bus. +However, it is possible that the driver needs to be probed +first so that it can enable corresponding SLIMbus device (e.g. power it up and/or +take it out of reset). To support that behavior, the framework allows drivers +to probe first as well (e.g. using standard DeviceTree compatibility field). +This creates the necessity for the driver to know when the device is functional +(i.e. reported present). device_up callback is used for that reason when the +device reports present and is assigned a logical address by the controller. + +Similarly, SLIMbus devices 'report absent' when they go down. A 'device_down' +callback notifies the driver when the device reports absent and its logical +address assignment is invalidated by the controller. + +Another notification "boot_device" is used to notify the slim_driver when +controller resets the bus. This notification allows the driver to take necessary +steps to boot the device so that it's functional after the bus has been reset. + +Driver and Controller APIs: +--------------------------- +.. kernel-doc:: include/linux/slimbus.h + :internal: + +.. kernel-doc:: drivers/slimbus/slimbus.h + :internal: + +.. kernel-doc:: drivers/slimbus/core.c + :export: + +Clock-pause: +------------ +SLIMbus mandates that a reconfiguration sequence (known as clock-pause) be +broadcast to all active devices on the bus before the bus can enter low-power +mode. Controller uses this sequence when it decides to enter low-power mode so +that corresponding clocks and/or power-rails can be turned off to save power. +Clock-pause is exited by waking up framer device (if controller driver initiates +exiting low power mode), or by toggling the data line (if a slave device wants +to initiate it). + +Clock-pause APIs: +~~~~~~~~~~~~~~~~~ +.. kernel-doc:: drivers/slimbus/sched.c + :export: + +Messaging: +---------- +The framework supports regmap and read/write apis to exchange control-information +with a SLIMbus device. APIs can be synchronous or asynchronous. +The header file <linux/slimbus.h> has more documentation about messaging APIs. + +Messaging APIs: +~~~~~~~~~~~~~~~ +.. kernel-doc:: drivers/slimbus/messaging.c + :export: + +Streaming APIs: +~~~~~~~~~~~~~~~ +.. kernel-doc:: drivers/slimbus/stream.c + :export: |
