| NOTE: |
| ===== |
| |
| While the driver probes the hardware and reports itself as a |
| V4L2 driver, there are still some issues preventing it to |
| stream (at least it doesn't with the standard V4L2 applications. |
| Didn't test yet with some custom-made app for this driver). |
| Solving the related bugs and issues preventing it to work is |
| needed (items 6 and 7 from the list below). |
| |
| TODO |
| ==== |
| |
| 1. The atomisp doesn't rely at the usual i2c stuff to discover the |
| sensors. Instead, it calls a function from atomisp_gmin_platform.c. |
| There are some hacks added there for it to wait for sensors to be |
| probed (with a timeout of 2 seconds or so). |
| This should be converted to the usual way, using V4L2 async subdev |
| framework to wait for cameras to be probed; |
| |
| 2. Use ACPI _DSM table - DONE! |
| |
| 3. Switch the driver to use pm_runtime stuff. Right now, it probes the |
| existing PMIC code and sensors call it directly. |
| |
| 4. There's a problem at the sensor drivers: when trying to set a video |
| format, the atomisp main driver calls the sensor drivers with the |
| sensor turned off. This causes them to fail. |
| |
| The only exception is the atomisp-ov2880, which has a hack inside it |
| to turn it on when VIDIOC_S_FMT is called. |
| |
| The right fix seems to power on the sensor when a video device is |
| opened (or at the first VIDIOC_ ioctl - except for VIDIOC_QUERYCAP), |
| powering it down at close() syscall. |
| |
| Such kind of control would need to be done inside the atomisp driver, |
| not at the sensors code. |
| |
| 5. There are several issues related to memory management, causing |
| crashes. The atomisp splits the memory management on three separate |
| regions: |
| |
| - dynamic pool; |
| - reserved pool; |
| - generic pool |
| |
| The code implementing it is at: |
| |
| drivers/staging/media/atomisp/pci/hmm/ |
| |
| It also has a separate code for managing DMA buffers at: |
| |
| drivers/staging/media/atomisp/pci/mmu/ |
| |
| The code there is really dirty, ugly and probably wrong. I fixed |
| one bug there already, but the best would be to just trash it and use |
| something else. Maybe the code from the newer intel driver could |
| serve as a model: |
| |
| drivers/staging/media/ipu3/ipu3-mmu.c |
| |
| But converting it to use something like that is painful and may |
| cause some breakages. |
| |
| 6. There is some issues at the frame receive logic, causing the |
| DQBUF ioctls to fail. |
| |
| 7. A single AtomISP driver needs to be implemented to support both |
| Baytrail (BYT) and Cherrytail (CHT) platforms at the same time. |
| The current driver is a mechanical and hand combined merge of the |
| two using several runtime macros, plus some ifdef ISP2401 to select the |
| CHT version. Yet, there are some ISP-specific headers that change the |
| driver's behavior during compile time. |
| |
| 8. The file structure needs to get tidied up to resemble a normal Linux |
| driver. |
| |
| 9. Lots of the midlayer glue. unused code and abstraction needs removing. |
| |
| 10. The AtomISP driver includes some special IOCTLS (ATOMISP_IOC_XXXX_XXXX) |
| and controls that require some cleanup. Some of those code may have |
| been removed during the cleanups. They could be needed in order to |
| properly support 3A algorithms |
| |
| Such IOCTL interface needs more documentation. The better would |
| be to use something close to the interface used by the IPU3 IMGU driver. |
| |
| 11. The ISP code has some dependencies of the exact FW version. |
| The version defined in pci/sh_css_firmware.c: |
| |
| BYT (isp2400): "irci_stable_candrpv_0415_20150521_0458" |
| |
| CHT (isp2401): "irci_ecr - master_20150911_0724" |
| |
| Those versions don't seem to be available anymore. On the tests we've |
| done so far, this version also seems to work for CHT: |
| |
| "irci_stable_candrpv_0415_20150521_0458" |
| |
| Which can be obtainable from Yocto Atom ISP respository. |
| |
| but this was not thoroughly tested. |
| |
| At some point we may need to round up a few driver versions and see if |
| there are any specific things that can be done to fold in support for |
| multiple firmware versions. |
| |
| 12. Switch to standard V4L2 sub-device API for sensor and lens. In |
| particular, the user space API needs to support V4L2 controls as |
| defined in the V4L2 spec and references to atomisp must be removed from |
| these drivers. |
| |
| 13. Use LED flash API for flash LED drivers such as LM3554 (which already |
| has a LED class driver). |
| |
| 14. Switch from videobuf1 to videobuf2. Videobuf1 is being removed! |
| |
| 15. Correct Coding Style. Please refrain sending coding style patches |
| for this driver until the other work is done, as there will be a lot |
| of code churn until this driver becomes functional again. |
| |
| Limitations |
| =========== |
| |
| 1. To test the patches, you also need the ISP firmware |
| |
| for BYT: /lib/firmware/shisp_2400b0_v21.bin |
| for CHT: /lib/firmware/shisp_2401a0_v21.bin |
| |
| The firmware files will usually be found in /etc/firmware on an Android |
| device but can also be extracted from the upgrade kit if you've managed |
| to lose them somehow. |
| |
| 2. Without a 3A library the capture behaviour is not very good. To take a good |
| picture, you need tune ISP parameters by IOCTL functions or use a 3A library |
| such as libxcam. |
| |
| 3. The driver is intended to drive the PCI exposed versions of the device. |
| It will not detect those devices enumerated via ACPI as a field of the |
| i915 GPU driver. |
| |
| There are some patches adding i915 GPU support floating at the Yocto's |
| Aero repository (so far, untested upstream). |
| |
| 4. The driver supports only v2 of the IPU/Camera. It will not work with the |
| versions of the hardware in other SoCs. |