Hi Kaaira, On 31/07/2020 18:22, Kaaira Gupta wrote: > Hi everyone, > > On Wed, Jul 29, 2020 at 05:24:25PM +0200, Dafna Hirschfeld wrote: >> >> >> On 29.07.20 15:27, Kieran Bingham wrote: >>> Hi Dafna, Kaaira, >>> >>> On 29/07/2020 14:16, Dafna Hirschfeld wrote: >>>> >>>> >>>> On 29.07.20 15:05, Kieran Bingham wrote: >>>>> Hi Dafna, >>>>> >>>>> On 28/07/2020 15:00, Dafna Hirschfeld wrote: >>>>>> >>>>>> >>>>>> On 28.07.20 14:07, Dafna Hirschfeld wrote: >>>>>>> Hi >>>>>>> >>>>>>> On 28.07.20 13:39, Kaaira Gupta wrote: >>>>>>>> On Mon, Jul 27, 2020 at 02:54:30PM -0300, Helen Koike wrote: >>>>>>>>> Hi, >>>>>>>>> >>>>>>>>> On 7/27/20 11:31 AM, Kieran Bingham wrote: >>>>>>>>>> Hi all, >>>>>>>>>> >>>>>>>>>> +Dafna for the thread discussion, as she's missed from the to/cc >>>>>>>>>> list. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On 24/07/2020 13:21, Kaaira Gupta wrote: >>>>>>>>>>> On Fri, Jul 24, 2020 at 02:15:21PM +0200, Niklas Söderlund wrote: >>>>>>>>>>> Hi, >>>>>>>>>>> >>>>>>>>>>>> Hi Kaaira, >>>>>>>>>>>> >>>>>>>>>>>> Thanks for your work. >>>>>>>>>>> >>>>>>>>>>> Thanks for yours :D >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> On 2020-07-24 17:32:10 +0530, Kaaira Gupta wrote: >>>>>>>>>>>>> This is version 2 of the patch series posted by Niklas for >>>>>>>>>>>>> allowing >>>>>>>>>>>>> multiple streams in VIMC. >>>>>>>>>>>>> The original series can be found here: >>>>>>>>>>>>> https://patchwork.kernel.org/cover/10948831/ >>>>>>>>>>>>> >>>>>>>>>>>>> This series adds support for two (or more) capture devices to be >>>>>>>>>>>>> connected to the same sensors and run simultaneously. Each >>>>>>>>>>>>> capture device >>>>>>>>>>>>> can be started and stopped independent of each other. >>>>>>>>>>>>> >>>>>>>>>>>>> Patch 1/3 and 2/3 deals with solving the issues that arises once >>>>>>>>>>>>> two >>>>>>>>>>>>> capture devices can be part of the same pipeline. While 3/3 >>>>>>>>>>>>> allows for >>>>>>>>>>>>> two capture devices to be part of the same pipeline and thus >>>>>>>>>>>>> allows for >>>>>>>>>>>>> simultaneously use. >>>>>>> >>>>>>> I wonder if these two patches are enough, since each vimc entity also >>>>>>> have >>>>>>> a 'process_frame' callback, but only one allocated frame. That means >>>>>>> that the 'process_frame' can be called concurrently by two different >>>>>>> streams >>>>>>> on the same frame and cause corruption. >>>>>>> >>>>>> >>>>>> I think we should somehow change the vimc-stream.c code so that we have >>>>>> only >>>>>> one stream process per pipe. So if one capture is already streaming, >>>>>> then the new >>>>>> capture that wants to stream uses the same thread so we don't have two >>>>>> threads >>>>>> both calling 'process_frame'. >>>>> >>>>> >>>>> Yes, I think it looks and sounds like there are two threads running when >>>>> there are two streams. >>>>> >>>>> so in effect, although they 'share a pipe', aren't they in effect just >>>>> sending two separate buffers through their stream-path? >>>>> >>>>> If that's the case, then I don't think there's any frame corruption, >>>>> because they would both have grabbed their own frame separately. >>>> >>>> But each entity allocates just one buffer. So the same buffer is used for >>>> both stream. >>> >>> Aha, ok, I hadn't realised there was only a single buffer available in >>> the pipeline for each entity. Indeed there is a risk of corruption in >>> that case. >>> >>>> What for example can happen is that the debayer of one stream can read the >>>> sensor's buffer while the sensor itself writes to the buffer for the other >>>> stream. >>> >>> >>> So, In that case, we have currently got a scenario where each 'stream' >>> really is operating it's own pipe (even though all components are reused). >>> >>> Two questions: >>> >>> Is this acceptable, and we should just use a mutex to ensure the buffers >>> are not corrupted, but essentially each stream is a separate temporal >>> capture? >>> >>> >>> Or B: >>> >>> Should we refactor to make sure that there is a single thread, and the >>> code which calls process_frame on each entity should become aware of the >>> potential for multiple paths at the point of the sensor. >>> >>> >>> I suspect option B is really the 'right' path to take, but it is more >>> complicated of course. >> >> I also think option B is preferable. >> >> Maybe we can add a bool field 'is_streaming' to struct 'vimc_ent_device' >> The stream thread can do a BFS scan from the sensor up to the captures >> and call the 'process_frame' for each entity if 'is_streaming == true'. >> When a new capture wants to stream it sets 'is_streaming = true' >> on the entities on his streaming path. > > It is s_stream(enable) that initialises a streaming pipeline, ie the one with > those components of the pipeline which are in stream path and then runs a > thread which calls process_frame on each and passes the frame to the > next entity in streaming pipeline. So currently, one thread is for one > "streaming pipeline". So there are two options I can think of if a > single thread is required, > > 1. Not creating a streaming pipeline, rather create a graph(?) which > connects both say Raw capture 1 and debayer B to sensor B if two streams > are asked for, and only one of them if one stream is asked..that will > not be a property of streamer, so I am not sure where it should be kept. > Then I could move creating a thread out of s_stream. Creating the thread > should wait for entire pipeline to be created, ie s_stream(enable) to > must be called by both the captures, and a graph made of all pipeline > components before thread initialisation starts. I am not sure how this > should be implemented. The graph already exists, and can be walked through the media controller right? > 2. Another option is to check if a stream already exists (by creating it > a property of vimc to keep a track of no. of streams maybe?), if it is > already present I could take the previous output of sensor (but > then it will have to be stored, so i don't think this is a nice idea), > and use it further (but thread will be different in this case). I don't think I understand this one... > What can be a better design for VIMC to have a single thread if two > streams are asked (apart/of the options I mentioned)? How about adding a count in s_stream so that the thread only gets started when the use count is > 0, and stopped when the usage < 1. That handles making sure that only one thread is available. All calls into s_stream() will need to take a lock/mutex to protect / prevent any action from occurring while the thread is performing a process of the pipeline. static int vimc_streamer_thread(void *data) { struct vimc_stream *stream = data; u8 *frame = NULL; int i; set_freezable(); for (;;) { try_to_freeze(); if (kthread_should_stop()) break; + /* take lock shared with s_stream */ for (i = stream->pipe_size - 1; i >= 0; i--) { frame = stream->ved_pipeline[i]->process_frame( stream->ved_pipeline[i], frame); if (!frame || IS_ERR(frame)) break; } + /* Release lock/mutex shared with s_stream //wait for 60hz set_current_state(TASK_UNINTERRUPTIBLE); schedule_timeout(HZ / 60); } return 0; } And you'll need to make the code which processes the pipeline aware of the fact that there may be two pipelines to fulfil: Pseudo patch/code: static int vimc_streamer_thread(void *data) { - struct vimc_stream *stream = data; + /* Something which knows about the whole device */ + struct xxxxx *yyy = data; + u8 *raw; u8 *frame = NULL; int i; set_freezable(); for (;;) { try_to_freeze(); if (kthread_should_stop()) break; /* take lock shared with s_stream */ + /* Process the sensor first */ + raw = stream->ved_pipeline[sensor]->process_frame(..); + error check; + /* (If connected) Process stream 1 */ + if (raw) + frame = stream->ved_pipeline[raw]->process_frame(); + error check; + /* If connected process the rest of the pipe */ + for (i = after sensor; end_entity; i++) { frame = stream->ved_pipeline[i]->process_frame( stream->ved_pipeline[i], frame); if (!frame || IS_ERR(frame)) break; } /* Release lock/mutex shared with s_stream //wait for 60hz set_current_state(TASK_UNINTERRUPTIBLE); schedule_timeout(HZ / 60); } return 0; } I may have missed something as the original loop was decrementing and going backwards through the entities in stream->ved_pipeline. I guess splitting that all out so instead it starts at the sensor, and just walks the graph (handling any running/connected fork to two entities appropriately) in a neater way would be another option rather than hardcoding it, but either way the thread needs to operate at the device level rather than the stream level. > Thanks > Kaaira > >> >> Thanks, >> Dafna >> >> >>> >>> -- >>> Kieran >>> >>> >>> >>> >>>> Thanks, >>>> Dafna >>>> >>>>> >>>>> >>>>> I don't think that's a good example of the hardware though, as that >>>>> doesn't reflect what 'should' happen where the TPG runs once to generate >>>>> a frame at the sensor, which is then read by both the debayer entity and >>>>> the RAW capture device when there are two streams... >>>>> >>>>> >>>>> So I suspect trying to move to a single thread is desirable, but that >>>>> might be a fair bit of work also. >>>>> >>>>> -- >>>>> Kieran >>>>> >>>>> >>>>> >>>>>> The second capture that wants to stream should iterate the topology >>>>>> downwards until >>>>>> reaching an entity that already belong to the stream path of the other >>>>>> streaming capture >>>>>> and tell the streamer it wants to read the frames this entity >>>>>> produces. >>>>>> >>>>>> Thanks, >>>>>> Dafna >>>>>> >>>>>>> Thanks, >>>>>>> Dafna >>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> I'm just curious if you are aware of this series? It would >>>>>>>>>>>> replace the >>>>>>>>>>>> need for 1/3 and 2/3 of this series right? >>>>>>>>>>> >>>>>>>>>>> v3 of this series replaces the need for 1/3, but not the current >>>>>>>>>>> version >>>>>>>>>>> (ie v4). v4 of patch 2/5 removes the stream_counter that is >>>>>>>>>>> needed to >>>>>>>>>>> keep count of the calls to s_stream. Hence 1/3 becomes relevant >>>>>>>>>>> again. >>>>>>>>>> >>>>>>>>>> So the question really is, how do we best make use of the two >>>>>>>>>> current >>>>>>>>>> series, to achieve our goal of supporting multiple streams. >>>>>>>>>> >>>>>>>>>> Having not parsed Dafna's series yet, do we need to combine >>>>>>>>>> elements of >>>>>>>>>> both ? Or should we work towards starting with this series and get >>>>>>>>>> dafna's patches built on top ? >>>>>>>>>> >>>>>>>>>> Or should patch 1/3 and 3/3 of this series be on top of Dafna's v4 ? >>>>>>>>>> >>>>>>>>>> (It might be noteworthy to say that Kaaira has reported successful >>>>>>>>>> multiple stream operation from /this/ series and her development >>>>>>>>>> branch >>>>>>>>>> on libcamera). >>>>>>>>> >>>>>>>>> Dafna's patch seems still under discussion, but I don't want to >>>>>>>>> block progress in Vimc either. >>>>>>>>> >>>>>>>>> So I was wondering if we can move forward with Vimc support for >>>>>>>>> multistreaming, >>>>>>>>> without considering Dafna's patchset, and we can do the clean up >>>>>>>>> later once we solve that. >>>>>>>>> >>>>>>>>> What do you think? >>>>>>>> >>>>>>>> I agree with supporting multiple streams with VIMC with this patchset, >>>>>>>> and then we can refactor the counters for s_stream in VIMC later (over >>>>>>>> this series) if dafna includes them in subsequent version of her >>>>>>>> patchset. >>>>>>>> >>>>>>> >>>>>>> I also think that adding support in the code will take much longer and >>>>>>> should not >>>>>>> stop us from supporting vimc independently. >>>>>>> >>>>>>> Thanks, >>>>>>> Dafna >>>>>>> >>>>>>>>> >>>>>>>>> Regards, >>>>>>>>> Helen >>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>>> 1. >>>>>>>>>>>> https://lore.kernel.org/linux-media/20200522075522.6190-1-dafna.hirschfeld@xxxxxxxxxxxxx/ >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> Changes since v1: >>>>>>>>>>>>> - All three patches rebased on latest media-tree. >>>>>>>>>>>>> Patch 3: >>>>>>>>>>>>> - Search for an entity with a non-NULL pipe instead of >>>>>>>>>>>>> searching >>>>>>>>>>>>> for sensor. This terminates the search at output itself. >>>>>>>>>>>>> >>>>>>>>>>>>> Kaaira Gupta (3): >>>>>>>>>>>>> media: vimc: Add usage count to subdevices >>>>>>>>>>>>> media: vimc: Serialize vimc_streamer_s_stream() >>>>>>>>>>>>> media: vimc: Join pipeline if one already exists >>>>>>>>>>>>> >>>>>>>>>>>>> .../media/test-drivers/vimc/vimc-capture.c | 35 >>>>>>>>>>>>> ++++++++++++++++++- >>>>>>>>>>>>> .../media/test-drivers/vimc/vimc-debayer.c | 8 +++++ >>>>>>>>>>>>> drivers/media/test-drivers/vimc/vimc-scaler.c | 8 +++++ >>>>>>>>>>>>> drivers/media/test-drivers/vimc/vimc-sensor.c | 9 ++++- >>>>>>>>>>>>> .../media/test-drivers/vimc/vimc-streamer.c | 23 >>>>>>>>>>>>> +++++++----- >>>>>>>>>>>>> 5 files changed, 73 insertions(+), 10 deletions(-) >>>>>>>>>>>>> >>>>>>>>>>>>> -- >>>>>>>>>>>>> 2.17.1 >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> -- >>>>>>>>>>>> Regards, >>>>>>>>>>>> Niklas Söderlund >>>>>>>>>> >>>>> >>> -- Regards -- Kieran
