| Samsung S5P/EXYNOS4 FIMC driver | |
| Copyright (C) 2012 - 2013 Samsung Electronics Co., Ltd. | |
| --------------------------------------------------------------------------- | |
| The FIMC (Fully Interactive Mobile Camera) device available in Samsung | |
| SoC Application Processors is an integrated camera host interface, color | |
| space converter, image resizer and rotator. It's also capable of capturing | |
| data from LCD controller (FIMD) through the SoC internal writeback data | |
| path. There are multiple FIMC instances in the SoCs (up to 4), having | |
| slightly different capabilities, like pixel alignment constraints, rotator | |
| availability, LCD writeback support, etc. The driver is located at | |
| drivers/media/platform/exynos4-is directory. | |
| 1. Supported SoCs | |
| ================= | |
| S5PC100 (mem-to-mem only), S5PV210, EXYNOS4210 | |
| 2. Supported features | |
| ===================== | |
| - camera parallel interface capture (ITU-R.BT601/565); | |
| - camera serial interface capture (MIPI-CSI2); | |
| - memory-to-memory processing (color space conversion, scaling, mirror | |
| and rotation); | |
| - dynamic pipeline re-configuration at runtime (re-attachment of any FIMC | |
| instance to any parallel video input or any MIPI-CSI front-end); | |
| - runtime PM and system wide suspend/resume | |
| Not currently supported: | |
| - LCD writeback input | |
| - per frame clock gating (mem-to-mem) | |
| 3. Files partitioning | |
| ===================== | |
| - media device driver | |
| drivers/media/platform/exynos4-is/media-dev.[ch] | |
| - camera capture video device driver | |
| drivers/media/platform/exynos4-is/fimc-capture.c | |
| - MIPI-CSI2 receiver subdev | |
| drivers/media/platform/exynos4-is/mipi-csis.[ch] | |
| - video post-processor (mem-to-mem) | |
| drivers/media/platform/exynos4-is/fimc-core.c | |
| - common files | |
| drivers/media/platform/exynos4-is/fimc-core.h | |
| drivers/media/platform/exynos4-is/fimc-reg.h | |
| drivers/media/platform/exynos4-is/regs-fimc.h | |
| 4. User space interfaces | |
| ======================== | |
| 4.1. Media device interface | |
| The driver supports Media Controller API as defined at | |
| http://linuxtv.org/downloads/v4l-dvb-apis/media_common.html | |
| The media device driver name is "SAMSUNG S5P FIMC". | |
| The purpose of this interface is to allow changing assignment of FIMC instances | |
| to the SoC peripheral camera input at runtime and optionally to control internal | |
| connections of the MIPI-CSIS device(s) to the FIMC entities. | |
| The media device interface allows to configure the SoC for capturing image | |
| data from the sensor through more than one FIMC instance (e.g. for simultaneous | |
| viewfinder and still capture setup). | |
| Reconfiguration is done by enabling/disabling media links created by the driver | |
| during initialization. The internal device topology can be easily discovered | |
| through media entity and links enumeration. | |
| 4.2. Memory-to-memory video node | |
| V4L2 memory-to-memory interface at /dev/video? device node. This is standalone | |
| video device, it has no media pads. However please note the mem-to-mem and | |
| capture video node operation on same FIMC instance is not allowed. The driver | |
| detects such cases but the applications should prevent them to avoid an | |
| undefined behaviour. | |
| 4.3. Capture video node | |
| The driver supports V4L2 Video Capture Interface as defined at: | |
| http://linuxtv.org/downloads/v4l-dvb-apis/devices.html | |
| At the capture and mem-to-mem video nodes only the multi-planar API is | |
| supported. For more details see: | |
| http://linuxtv.org/downloads/v4l-dvb-apis/planar-apis.html | |
| 4.4. Camera capture subdevs | |
| Each FIMC instance exports a sub-device node (/dev/v4l-subdev?), a sub-device | |
| node is also created per each available and enabled at the platform level | |
| MIPI-CSI receiver device (currently up to two). | |
| 4.5. sysfs | |
| In order to enable more precise camera pipeline control through the sub-device | |
| API the driver creates a sysfs entry associated with "s5p-fimc-md" platform | |
| device. The entry path is: /sys/platform/devices/s5p-fimc-md/subdev_conf_mode. | |
| In typical use case there could be a following capture pipeline configuration: | |
| sensor subdev -> mipi-csi subdev -> fimc subdev -> video node | |
| When we configure these devices through sub-device API at user space, the | |
| configuration flow must be from left to right, and the video node is | |
| configured as last one. | |
| When we don't use sub-device user space API the whole configuration of all | |
| devices belonging to the pipeline is done at the video node driver. | |
| The sysfs entry allows to instruct the capture node driver not to configure | |
| the sub-devices (format, crop), to avoid resetting the subdevs' configuration | |
| when the last configuration steps at the video node is performed. | |
| For full sub-device control support (subdevs configured at user space before | |
| starting streaming): | |
| # echo "sub-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode | |
| For V4L2 video node control only (subdevs configured internally by the host | |
| driver): | |
| # echo "vid-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode | |
| This is a default option. | |
| 5. Device mapping to video and subdev device nodes | |
| ================================================== | |
| There are associated two video device nodes with each device instance in | |
| hardware - video capture and mem-to-mem and additionally a subdev node for | |
| more precise FIMC capture subsystem control. In addition a separate v4l2 | |
| sub-device node is created per each MIPI-CSIS device. | |
| How to find out which /dev/video? or /dev/v4l-subdev? is assigned to which | |
| device? | |
| You can either grep through the kernel log to find relevant information, i.e. | |
| # dmesg | grep -i fimc | |
| (note that udev, if present, might still have rearranged the video nodes), | |
| or retrieve the information from /dev/media? with help of the media-ctl tool: | |
| # media-ctl -p | |
| 6. Platform support | |
| =================== | |
| The machine code (arch/arm/plat-samsung and arch/arm/mach-*) must select | |
| following options: | |
| CONFIG_S5P_DEV_FIMC0 mandatory | |
| CONFIG_S5P_DEV_FIMC1 \ | |
| CONFIG_S5P_DEV_FIMC2 | optional | |
| CONFIG_S5P_DEV_FIMC3 | | |
| CONFIG_S5P_SETUP_FIMC / | |
| CONFIG_S5P_SETUP_MIPIPHY \ | |
| CONFIG_S5P_DEV_CSIS0 | optional for MIPI-CSI interface | |
| CONFIG_S5P_DEV_CSIS1 / | |
| Except that, relevant s5p_device_fimc? should be registered in the machine code | |
| in addition to a "s5p-fimc-md" platform device to which the media device driver | |
| is bound. The "s5p-fimc-md" device instance is required even if only mem-to-mem | |
| operation is used. | |
| The description of sensor(s) attached to FIMC/MIPI-CSIS camera inputs should be | |
| passed as the "s5p-fimc-md" device platform_data. The platform data structure | |
| is defined in file include/media/s5p_fimc.h. | |
| 7. Build | |
| ======== | |
| This driver depends on following config options: | |
| PLAT_S5P, | |
| PM_RUNTIME, | |
| I2C, | |
| REGULATOR, | |
| VIDEO_V4L2_SUBDEV_API, | |
| If the driver is built as a loadable kernel module (CONFIG_VIDEO_SAMSUNG_S5P_FIMC=m) | |
| two modules are created (in addition to the core v4l2 modules): s5p-fimc.ko and | |
| optional s5p-csis.ko (MIPI-CSI receiver subdev). |