| OMAP 3 Image Signal Processor (ISP) driver |
| |
| Copyright (C) 2010 Nokia Corporation |
| Copyright (C) 2009 Texas Instruments, Inc. |
| |
| Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com> |
| Sakari Ailus <sakari.ailus@iki.fi> |
| David Cohen <dacohen@gmail.com> |
| |
| |
| Introduction |
| ============ |
| |
| This file documents the Texas Instruments OMAP 3 Image Signal Processor (ISP) |
| driver located under drivers/media/video/omap3isp. The original driver was |
| written by Texas Instruments but since that it has been rewritten (twice) at |
| Nokia. |
| |
| The driver has been successfully used on the following versions of OMAP 3: |
| |
| 3430 |
| 3530 |
| 3630 |
| |
| The driver implements V4L2, Media controller and v4l2_subdev interfaces. |
| Sensor, lens and flash drivers using the v4l2_subdev interface in the kernel |
| are supported. |
| |
| |
| Split to subdevs |
| ================ |
| |
| The OMAP 3 ISP is split into V4L2 subdevs, each of the blocks inside the ISP |
| having one subdev to represent it. Each of the subdevs provide a V4L2 subdev |
| interface to userspace. |
| |
| OMAP3 ISP CCP2 |
| OMAP3 ISP CSI2a |
| OMAP3 ISP CCDC |
| OMAP3 ISP preview |
| OMAP3 ISP resizer |
| OMAP3 ISP AEWB |
| OMAP3 ISP AF |
| OMAP3 ISP histogram |
| |
| Each possible link in the ISP is modelled by a link in the Media controller |
| interface. For an example program see [2]. |
| |
| |
| Controlling the OMAP 3 ISP |
| ========================== |
| |
| In general, the settings given to the OMAP 3 ISP take effect at the beginning |
| of the following frame. This is done when the module becomes idle during the |
| vertical blanking period on the sensor. In memory-to-memory operation the pipe |
| is run one frame at a time. Applying the settings is done between the frames. |
| |
| All the blocks in the ISP, excluding the CSI-2 and possibly the CCP2 receiver, |
| insist on receiving complete frames. Sensors must thus never send the ISP |
| partial frames. |
| |
| Autoidle does have issues with some ISP blocks on the 3430, at least. |
| Autoidle is only enabled on 3630 when the omap3isp module parameter autoidle |
| is non-zero. |
| |
| |
| Events |
| ====== |
| |
| The OMAP 3 ISP driver does support the V4L2 event interface on CCDC and |
| statistics (AEWB, AF and histogram) subdevs. |
| |
| The CCDC subdev produces V4L2_EVENT_OMAP3ISP_HS_VS type event on HS_VS |
| interrupt which is used to signal frame start. The event is triggered exactly |
| when the reception of the first line of the frame starts in the CCDC module. |
| The event can be subscribed on the CCDC subdev. |
| |
| (When using parallel interface one must pay account to correct configuration |
| of the VS signal polarity. This is automatically correct when using the serial |
| receivers.) |
| |
| Each of the statistics subdevs is able to produce events. An event is |
| generated whenever a statistics buffer can be dequeued by a user space |
| application using the VIDIOC_OMAP3ISP_STAT_REQ IOCTL. The events available |
| are: |
| |
| V4L2_EVENT_OMAP3ISP_AEWB |
| V4L2_EVENT_OMAP3ISP_AF |
| V4L2_EVENT_OMAP3ISP_HIST |
| |
| The type of the event data is struct omap3isp_stat_event_status for these |
| ioctls. If there is an error calculating the statistics, there will be an |
| event as usual, but no related statistics buffer. In this case |
| omap3isp_stat_event_status.buf_err is set to non-zero. |
| |
| |
| Private IOCTLs |
| ============== |
| |
| The OMAP 3 ISP driver supports standard V4L2 IOCTLs and controls where |
| possible and practical. Much of the functions provided by the ISP, however, |
| does not fall under the standard IOCTLs --- gamma tables and configuration of |
| statistics collection are examples of such. |
| |
| In general, there is a private ioctl for configuring each of the blocks |
| containing hardware-dependent functions. |
| |
| The following private IOCTLs are supported: |
| |
| VIDIOC_OMAP3ISP_CCDC_CFG |
| VIDIOC_OMAP3ISP_PRV_CFG |
| VIDIOC_OMAP3ISP_AEWB_CFG |
| VIDIOC_OMAP3ISP_HIST_CFG |
| VIDIOC_OMAP3ISP_AF_CFG |
| VIDIOC_OMAP3ISP_STAT_REQ |
| VIDIOC_OMAP3ISP_STAT_EN |
| |
| The parameter structures used by these ioctls are described in |
| include/linux/omap3isp.h. The detailed functions of the ISP itself related to |
| a given ISP block is described in the Technical Reference Manuals (TRMs) --- |
| see the end of the document for those. |
| |
| While it is possible to use the ISP driver without any use of these private |
| IOCTLs it is not possible to obtain optimal image quality this way. The AEWB, |
| AF and histogram modules cannot be used without configuring them using the |
| appropriate private IOCTLs. |
| |
| |
| CCDC and preview block IOCTLs |
| ============================= |
| |
| The VIDIOC_OMAP3ISP_CCDC_CFG and VIDIOC_OMAP3ISP_PRV_CFG IOCTLs are used to |
| configure, enable and disable functions in the CCDC and preview blocks, |
| respectively. Both IOCTLs control several functions in the blocks they |
| control. VIDIOC_OMAP3ISP_CCDC_CFG IOCTL accepts a pointer to struct |
| omap3isp_ccdc_update_config as its argument. Similarly VIDIOC_OMAP3ISP_PRV_CFG |
| accepts a pointer to struct omap3isp_prev_update_config. The definition of |
| both structures is available in [1]. |
| |
| The update field in the structures tells whether to update the configuration |
| for the specific function and the flag tells whether to enable or disable the |
| function. |
| |
| The update and flag bit masks accept the following values. Each separate |
| functions in the CCDC and preview blocks is associated with a flag (either |
| disable or enable; part of the flag field in the structure) and a pointer to |
| configuration data for the function. |
| |
| Valid values for the update and flag fields are listed here for |
| VIDIOC_OMAP3ISP_CCDC_CFG. Values may be or'ed to configure more than one |
| function in the same IOCTL call. |
| |
| OMAP3ISP_CCDC_ALAW |
| OMAP3ISP_CCDC_LPF |
| OMAP3ISP_CCDC_BLCLAMP |
| OMAP3ISP_CCDC_BCOMP |
| OMAP3ISP_CCDC_FPC |
| OMAP3ISP_CCDC_CULL |
| OMAP3ISP_CCDC_CONFIG_LSC |
| OMAP3ISP_CCDC_TBL_LSC |
| |
| The corresponding values for the VIDIOC_OMAP3ISP_PRV_CFG are here: |
| |
| OMAP3ISP_PREV_LUMAENH |
| OMAP3ISP_PREV_INVALAW |
| OMAP3ISP_PREV_HRZ_MED |
| OMAP3ISP_PREV_CFA |
| OMAP3ISP_PREV_CHROMA_SUPP |
| OMAP3ISP_PREV_WB |
| OMAP3ISP_PREV_BLKADJ |
| OMAP3ISP_PREV_RGB2RGB |
| OMAP3ISP_PREV_COLOR_CONV |
| OMAP3ISP_PREV_YC_LIMIT |
| OMAP3ISP_PREV_DEFECT_COR |
| OMAP3ISP_PREV_GAMMABYPASS |
| OMAP3ISP_PREV_DRK_FRM_CAPTURE |
| OMAP3ISP_PREV_DRK_FRM_SUBTRACT |
| OMAP3ISP_PREV_LENS_SHADING |
| OMAP3ISP_PREV_NF |
| OMAP3ISP_PREV_GAMMA |
| |
| The associated configuration pointer for the function may not be NULL when |
| enabling the function. When disabling a function the configuration pointer is |
| ignored. |
| |
| |
| Statistic blocks IOCTLs |
| ======================= |
| |
| The statistics subdevs do offer more dynamic configuration options than the |
| other subdevs. They can be enabled, disable and reconfigured when the pipeline |
| is in streaming state. |
| |
| The statistics blocks always get the input image data from the CCDC (as the |
| histogram memory read isn't implemented). The statistics are dequeueable by |
| the user from the statistics subdev nodes using private IOCTLs. |
| |
| The private IOCTLs offered by the AEWB, AF and histogram subdevs are heavily |
| reflected by the register level interface offered by the ISP hardware. There |
| are aspects that are purely related to the driver implementation and these are |
| discussed next. |
| |
| VIDIOC_OMAP3ISP_STAT_EN |
| ----------------------- |
| |
| This private IOCTL enables/disables a statistic module. If this request is |
| done before streaming, it will take effect as soon as the pipeline starts to |
| stream. If the pipeline is already streaming, it will take effect as soon as |
| the CCDC becomes idle. |
| |
| VIDIOC_OMAP3ISP_AEWB_CFG, VIDIOC_OMAP3ISP_HIST_CFG and VIDIOC_OMAP3ISP_AF_CFG |
| ----------------------------------------------------------------------------- |
| |
| Those IOCTLs are used to configure the modules. They require user applications |
| to have an in-depth knowledge of the hardware. Most of the fields explanation |
| can be found on OMAP's TRMs. The two following fields common to all the above |
| configure private IOCTLs require explanation for better understanding as they |
| are not part of the TRM. |
| |
| omap3isp_[h3a_af/h3a_aewb/hist]_config.buf_size: |
| |
| The modules handle their buffers internally. The necessary buffer size for the |
| module's data output depends on the requested configuration. Although the |
| driver supports reconfiguration while streaming, it does not support a |
| reconfiguration which requires bigger buffer size than what is already |
| internally allocated if the module is enabled. It will return -EBUSY on this |
| case. In order to avoid such condition, either disable/reconfigure/enable the |
| module or request the necessary buffer size during the first configuration |
| while the module is disabled. |
| |
| The internal buffer size allocation considers the requested configuration's |
| minimum buffer size and the value set on buf_size field. If buf_size field is |
| out of [minimum, maximum] buffer size range, it's clamped to fit in there. |
| The driver then selects the biggest value. The corrected buf_size value is |
| written back to user application. |
| |
| omap3isp_[h3a_af/h3a_aewb/hist]_config.config_counter: |
| |
| As the configuration doesn't take effect synchronously to the request, the |
| driver must provide a way to track this information to provide more accurate |
| data. After a configuration is requested, the config_counter returned to user |
| space application will be an unique value associated to that request. When |
| user application receives an event for buffer availability or when a new |
| buffer is requested, this config_counter is used to match a buffer data and a |
| configuration. |
| |
| VIDIOC_OMAP3ISP_STAT_REQ |
| ------------------------ |
| |
| Send to user space the oldest data available in the internal buffer queue and |
| discards such buffer afterwards. The field omap3isp_stat_data.frame_number |
| matches with the video buffer's field_count. |
| |
| |
| Technical reference manuals (TRMs) and other documentation |
| ========================================================== |
| |
| OMAP 3430 TRM: |
| <URL:http://focus.ti.com/pdfs/wtbu/OMAP34xx_ES3.1.x_PUBLIC_TRM_vZM.zip> |
| Referenced 2011-03-05. |
| |
| OMAP 35xx TRM: |
| <URL:http://www.ti.com/litv/pdf/spruf98o> Referenced 2011-03-05. |
| |
| OMAP 3630 TRM: |
| <URL:http://focus.ti.com/pdfs/wtbu/OMAP36xx_ES1.x_PUBLIC_TRM_vQ.zip> |
| Referenced 2011-03-05. |
| |
| DM 3730 TRM: |
| <URL:http://www.ti.com/litv/pdf/sprugn4h> Referenced 2011-03-06. |
| |
| |
| References |
| ========== |
| |
| [1] include/linux/omap3isp.h |
| |
| [2] http://git.ideasonboard.org/?p=media-ctl.git;a=summary |