1OMAP 3 Image Signal Processor (ISP) driver
2
3Copyright (C) 2010 Nokia Corporation
4Copyright (C) 2009 Texas Instruments, Inc.
5
6Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
7	  Sakari Ailus <sakari.ailus@iki.fi>
8	  David Cohen <dacohen@gmail.com>
9
10
11Introduction
12============
13
14This file documents the Texas Instruments OMAP 3 Image Signal Processor (ISP)
15driver located under drivers/media/platform/omap3isp. The original driver was
16written by Texas Instruments but since that it has been rewritten (twice) at
17Nokia.
18
19The driver has been successfully used on the following versions of OMAP 3:
20
21	3430
22	3530
23	3630
24
25The driver implements V4L2, Media controller and v4l2_subdev interfaces.
26Sensor, lens and flash drivers using the v4l2_subdev interface in the kernel
27are supported.
28
29
30Split to subdevs
31================
32
33The OMAP 3 ISP is split into V4L2 subdevs, each of the blocks inside the ISP
34having one subdev to represent it. Each of the subdevs provide a V4L2 subdev
35interface to userspace.
36
37	OMAP3 ISP CCP2
38	OMAP3 ISP CSI2a
39	OMAP3 ISP CCDC
40	OMAP3 ISP preview
41	OMAP3 ISP resizer
42	OMAP3 ISP AEWB
43	OMAP3 ISP AF
44	OMAP3 ISP histogram
45
46Each possible link in the ISP is modelled by a link in the Media controller
47interface. For an example program see [2].
48
49
50Controlling the OMAP 3 ISP
51==========================
52
53In general, the settings given to the OMAP 3 ISP take effect at the beginning
54of the following frame. This is done when the module becomes idle during the
55vertical blanking period on the sensor. In memory-to-memory operation the pipe
56is run one frame at a time. Applying the settings is done between the frames.
57
58All the blocks in the ISP, excluding the CSI-2 and possibly the CCP2 receiver,
59insist on receiving complete frames. Sensors must thus never send the ISP
60partial frames.
61
62Autoidle does have issues with some ISP blocks on the 3430, at least.
63Autoidle is only enabled on 3630 when the omap3isp module parameter autoidle
64is non-zero.
65
66
67Events
68======
69
70The OMAP 3 ISP driver does support the V4L2 event interface on CCDC and
71statistics (AEWB, AF and histogram) subdevs.
72
73The CCDC subdev produces V4L2_EVENT_FRAME_SYNC type event on HS_VS
74interrupt which is used to signal frame start. Earlier version of this
75driver used V4L2_EVENT_OMAP3ISP_HS_VS for this purpose. The event is
76triggered exactly when the reception of the first line of the frame starts
77in the CCDC module. The event can be subscribed on the CCDC subdev.
78
79(When using parallel interface one must pay account to correct configuration
80of the VS signal polarity. This is automatically correct when using the serial
81receivers.)
82
83Each of the statistics subdevs is able to produce events. An event is
84generated whenever a statistics buffer can be dequeued by a user space
85application using the VIDIOC_OMAP3ISP_STAT_REQ IOCTL. The events available
86are:
87
88	V4L2_EVENT_OMAP3ISP_AEWB
89	V4L2_EVENT_OMAP3ISP_AF
90	V4L2_EVENT_OMAP3ISP_HIST
91
92The type of the event data is struct omap3isp_stat_event_status for these
93ioctls. If there is an error calculating the statistics, there will be an
94event as usual, but no related statistics buffer. In this case
95omap3isp_stat_event_status.buf_err is set to non-zero.
96
97
98Private IOCTLs
99==============
100
101The OMAP 3 ISP driver supports standard V4L2 IOCTLs and controls where
102possible and practical. Much of the functions provided by the ISP, however,
103does not fall under the standard IOCTLs --- gamma tables and configuration of
104statistics collection are examples of such.
105
106In general, there is a private ioctl for configuring each of the blocks
107containing hardware-dependent functions.
108
109The following private IOCTLs are supported:
110
111	VIDIOC_OMAP3ISP_CCDC_CFG
112	VIDIOC_OMAP3ISP_PRV_CFG
113	VIDIOC_OMAP3ISP_AEWB_CFG
114	VIDIOC_OMAP3ISP_HIST_CFG
115	VIDIOC_OMAP3ISP_AF_CFG
116	VIDIOC_OMAP3ISP_STAT_REQ
117	VIDIOC_OMAP3ISP_STAT_EN
118
119The parameter structures used by these ioctls are described in
120include/linux/omap3isp.h. The detailed functions of the ISP itself related to
121a given ISP block is described in the Technical Reference Manuals (TRMs) ---
122see the end of the document for those.
123
124While it is possible to use the ISP driver without any use of these private
125IOCTLs it is not possible to obtain optimal image quality this way. The AEWB,
126AF and histogram modules cannot be used without configuring them using the
127appropriate private IOCTLs.
128
129
130CCDC and preview block IOCTLs
131=============================
132
133The VIDIOC_OMAP3ISP_CCDC_CFG and VIDIOC_OMAP3ISP_PRV_CFG IOCTLs are used to
134configure, enable and disable functions in the CCDC and preview blocks,
135respectively. Both IOCTLs control several functions in the blocks they
136control. VIDIOC_OMAP3ISP_CCDC_CFG IOCTL accepts a pointer to struct
137omap3isp_ccdc_update_config as its argument. Similarly VIDIOC_OMAP3ISP_PRV_CFG
138accepts a pointer to struct omap3isp_prev_update_config. The definition of
139both structures is available in [1].
140
141The update field in the structures tells whether to update the configuration
142for the specific function and the flag tells whether to enable or disable the
143function.
144
145The update and flag bit masks accept the following values. Each separate
146functions in the CCDC and preview blocks is associated with a flag (either
147disable or enable; part of the flag field in the structure) and a pointer to
148configuration data for the function.
149
150Valid values for the update and flag fields are listed here for
151VIDIOC_OMAP3ISP_CCDC_CFG. Values may be or'ed to configure more than one
152function in the same IOCTL call.
153
154        OMAP3ISP_CCDC_ALAW
155        OMAP3ISP_CCDC_LPF
156        OMAP3ISP_CCDC_BLCLAMP
157        OMAP3ISP_CCDC_BCOMP
158        OMAP3ISP_CCDC_FPC
159        OMAP3ISP_CCDC_CULL
160        OMAP3ISP_CCDC_CONFIG_LSC
161        OMAP3ISP_CCDC_TBL_LSC
162
163The corresponding values for the VIDIOC_OMAP3ISP_PRV_CFG are here:
164
165        OMAP3ISP_PREV_LUMAENH
166        OMAP3ISP_PREV_INVALAW
167        OMAP3ISP_PREV_HRZ_MED
168        OMAP3ISP_PREV_CFA
169        OMAP3ISP_PREV_CHROMA_SUPP
170        OMAP3ISP_PREV_WB
171        OMAP3ISP_PREV_BLKADJ
172        OMAP3ISP_PREV_RGB2RGB
173        OMAP3ISP_PREV_COLOR_CONV
174        OMAP3ISP_PREV_YC_LIMIT
175        OMAP3ISP_PREV_DEFECT_COR
176        OMAP3ISP_PREV_GAMMABYPASS
177        OMAP3ISP_PREV_DRK_FRM_CAPTURE
178        OMAP3ISP_PREV_DRK_FRM_SUBTRACT
179        OMAP3ISP_PREV_LENS_SHADING
180        OMAP3ISP_PREV_NF
181        OMAP3ISP_PREV_GAMMA
182
183The associated configuration pointer for the function may not be NULL when
184enabling the function. When disabling a function the configuration pointer is
185ignored.
186
187
188Statistic blocks IOCTLs
189=======================
190
191The statistics subdevs do offer more dynamic configuration options than the
192other subdevs. They can be enabled, disable and reconfigured when the pipeline
193is in streaming state.
194
195The statistics blocks always get the input image data from the CCDC (as the
196histogram memory read isn't implemented). The statistics are dequeueable by
197the user from the statistics subdev nodes using private IOCTLs.
198
199The private IOCTLs offered by the AEWB, AF and histogram subdevs are heavily
200reflected by the register level interface offered by the ISP hardware. There
201are aspects that are purely related to the driver implementation and these are
202discussed next.
203
204VIDIOC_OMAP3ISP_STAT_EN
205-----------------------
206
207This private IOCTL enables/disables a statistic module. If this request is
208done before streaming, it will take effect as soon as the pipeline starts to
209stream.  If the pipeline is already streaming, it will take effect as soon as
210the CCDC becomes idle.
211
212VIDIOC_OMAP3ISP_AEWB_CFG, VIDIOC_OMAP3ISP_HIST_CFG and VIDIOC_OMAP3ISP_AF_CFG
213-----------------------------------------------------------------------------
214
215Those IOCTLs are used to configure the modules. They require user applications
216to have an in-depth knowledge of the hardware. Most of the fields explanation
217can be found on OMAP's TRMs. The two following fields common to all the above
218configure private IOCTLs require explanation for better understanding as they
219are not part of the TRM.
220
221omap3isp_[h3a_af/h3a_aewb/hist]_config.buf_size:
222
223The modules handle their buffers internally. The necessary buffer size for the
224module's data output depends on the requested configuration. Although the
225driver supports reconfiguration while streaming, it does not support a
226reconfiguration which requires bigger buffer size than what is already
227internally allocated if the module is enabled. It will return -EBUSY on this
228case. In order to avoid such condition, either disable/reconfigure/enable the
229module or request the necessary buffer size during the first configuration
230while the module is disabled.
231
232The internal buffer size allocation considers the requested configuration's
233minimum buffer size and the value set on buf_size field. If buf_size field is
234out of [minimum, maximum] buffer size range, it's clamped to fit in there.
235The driver then selects the biggest value. The corrected buf_size value is
236written back to user application.
237
238omap3isp_[h3a_af/h3a_aewb/hist]_config.config_counter:
239
240As the configuration doesn't take effect synchronously to the request, the
241driver must provide a way to track this information to provide more accurate
242data. After a configuration is requested, the config_counter returned to user
243space application will be an unique value associated to that request. When
244user application receives an event for buffer availability or when a new
245buffer is requested, this config_counter is used to match a buffer data and a
246configuration.
247
248VIDIOC_OMAP3ISP_STAT_REQ
249------------------------
250
251Send to user space the oldest data available in the internal buffer queue and
252discards such buffer afterwards. The field omap3isp_stat_data.frame_number
253matches with the video buffer's field_count.
254
255
256Technical reference manuals (TRMs) and other documentation
257==========================================================
258
259OMAP 3430 TRM:
260<URL:http://focus.ti.com/pdfs/wtbu/OMAP34xx_ES3.1.x_PUBLIC_TRM_vZM.zip>
261Referenced 2011-03-05.
262
263OMAP 35xx TRM:
264<URL:http://www.ti.com/litv/pdf/spruf98o> Referenced 2011-03-05.
265
266OMAP 3630 TRM:
267<URL:http://focus.ti.com/pdfs/wtbu/OMAP36xx_ES1.x_PUBLIC_TRM_vQ.zip>
268Referenced 2011-03-05.
269
270DM 3730 TRM:
271<URL:http://www.ti.com/litv/pdf/sprugn4h> Referenced 2011-03-06.
272
273
274References
275==========
276
277[1] include/linux/omap3isp.h
278
279[2] http://git.ideasonboard.org/?p=media-ctl.git;a=summary
280