Go to advanced search

by msperl
Mon Mar 31, 2014 7:56 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

I am still fighting some race conditions and I am unsure how to resolve them: Seems as if sometimes updating a memory locations on the arm via: writel(data,address); dsb(); does not propagate to L2 Cache of RAM itself withing 20us. This means that a (freshly) linked "DMA" control-block is not recogn...
by msperl
Tue Mar 25, 2014 6:41 am
Forum: Bare metal, Assembly language
Topic: RPI and WIFI SD to deploy new bootcode.bin,...
Replies: 4
Views: 2186

Re: RPI and WIFI SD to deploy new bootcode.bin,...

An alternative, cheap and simple option is to use the Pi's built-in UART, and a 3.3v USB to Serial converter to establish a serial link to a PC and then have the boot loader download the kernel image via the serial link. True: uboot can do that for the arm portion, but I am talking about videocore ...
by msperl
Mon Mar 24, 2014 7:10 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: About the second sdcard host interface driver
Replies: 4
Views: 2054

Re: About the second sdcard host interface driver

Yes, but you miss my Point: as mentioned some of those pins are not exposed via pinheaders and thus you cannot access them on the rpi. So unless you design your own board with a bcm2835 chip exposing those pins you will not be able to make use of them. As for the base-register: the official document...
by msperl
Sun Mar 23, 2014 9:00 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

After some hardware issues which have been resolved (bad solder skills a year ago coming to bit me now) I found the time to do some more tests and found another "race condition" between DMA and an interrupt handler that results in stalled DMA. So here some measurements compiling the "out of tree mod...
by msperl
Sat Mar 22, 2014 9:15 am
Forum: Bare metal, Assembly language
Topic: RPI and WIFI SD to deploy new bootcode.bin,...
Replies: 4
Views: 2186

RPI and WIFI SD to deploy new bootcode.bin,...

Hi! I thought of start investigating a "freeware" bootloader/FreeRTOS setup for the RPI (as a I doubt that linux will be possible due to the limited MMU capabilities of VC4 itself). Actually my first Idea would be trying to port uboot... To avoid having to manually unplug/replug the SD Card every ti...
by msperl
Fri Mar 21, 2014 12:29 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: CAN controller
Replies: 814
Views: 342465

Re: CAN controller

Hi! One thing that I find surprizing is that you do NOT get the interrupt 195 listed in /proc/interrupts. And last but not least cat /proc/interrupts CPU0 3: 21469 ARMCTRL BCM2708 Timer Tick 32: 307108 ARMCTRL dwc_otg, dwc_otg_pcd, dwc_otg_hcd:usb1 52: 0 ARMCTRL BCM2708 GPIO catchall handler 65: 2 A...
by msperl
Fri Mar 21, 2014 12:05 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: About the second sdcard host interface driver
Replies: 4
Views: 2054

Re: About the second sdcard host interface driver

For the same reason that there is no second UART or SPI devices: the required pins are not (completely) accessible. If you look in the Peripherals Document on page 101/102 you will find those Alternate functions. And there you can find that you would need the whole bank GPIO22-27 to make SD1 work (C...
by msperl
Thu Mar 20, 2014 1:37 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

Update: I believe I found the reason for those "stalls" - it was a race condition between DMA and interrupts. right now I got a solution that "seems" to work, but worsted case i will need to implement dma interrupts via a separate DMA channel to 100% solve the issue. Still - the issue has not shown ...
by msperl
Tue Mar 18, 2014 6:55 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

As said: you still have to have a driver that is optimized to make use of those features (especially optimize)... But with ADCs typically the problem is that of scheduling the transfers with minimal jitter and that becomes a problem. The driver includes copying a 64Bit timestamp (based on a 1MHz clo...
by msperl
Tue Mar 18, 2014 5:46 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

Just an update The DMA driver starts to work - there are still issues with the "spi_message_optimize" code. But some details on the driver: everything (Speed, delays,...) are programmed via DMA - no interaction. any GPIO can get used as ChipSelect - we are no longer limited to 2 SPI Devices on the b...
by msperl
Sun Mar 16, 2014 5:20 pm
Forum: Bare metal, Assembly language
Topic: Complete VideoCore Register map extracted from GPU sources
Replies: 7
Views: 3598

Re: Complete VideoCore Register map extracted from GPU sourc

Take the source of the perl-script provided on git-hub and add the transform of your choice (besides the existing ones to html, wikimedia and markdown)

Martin
by msperl
Thu Mar 06, 2014 12:52 pm
Forum: Bare metal, Assembly language
Topic: Complete VideoCore Register map extracted from GPU sources
Replies: 7
Views: 3598

Re: Complete VideoCore Register map extracted from GPU sourc

OK, I have created a Media Wiki transform as well and added its output to elinux wiki.
Most specifically: http://elinux.org/BCM2835_registers

Please add comment on any register that you know about and which is not documented in the Broadcom document.
by msperl
Thu Mar 06, 2014 8:37 am
Forum: Bare metal, Assembly language
Topic: Complete VideoCore Register map extracted from GPU sources
Replies: 7
Views: 3598

Re: Complete VideoCore Register map extracted from GPU sourc

I tried to get the sticky thread updated to get the errata (http://elinux.org/BCM2835_datasheet_errata) also linked - that did not happen either... I believe we should get it on a wiki for easier maintenance first. Which wiki? elinux maybe? Also what would be the ideal fields we should provide per r...
by msperl
Wed Mar 05, 2014 12:13 pm
Forum: Bare metal, Assembly language
Topic: Complete VideoCore Register map extracted from GPU sources
Replies: 7
Views: 3598

Re: Complete VideoCore Register map extracted from GPU sourc

OK - the (github) markeddown version has also been created.
by msperl
Wed Mar 05, 2014 10:23 am
Forum: Bare metal, Assembly language
Topic: Complete VideoCore Register map extracted from GPU sources
Replies: 7
Views: 3598

Complete VideoCore Register map extracted from GPU sources

Hi! Just want to let you know that I have converted the headers from the Broadcom GPU source code into a (hopefully) more readable html page. It should be mostly complete as it contains everything that is defined in the sources headers... And it contains interesting register ranges called: SD - for ...
by msperl
Sun Feb 23, 2014 8:58 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

The reason for the optimize call is to minimize the CPU overhead needed for transforming/verifying spi messages only once and not every time. Even the simple "verify" spi message function that runs on most spi-async takes on the rpi a ms - depending on complexity. And if you then have to transform t...
by msperl
Sun Feb 23, 2014 1:02 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

Tanks for the Info: For most parts your driver should immediately benefit from the dma - actually not the driver, but the system should require less CPU overall as there are no interrupts involved. But from what I just read what I would recommend is: A) use a fixed data structure that you do not hav...
by msperl
Sat Feb 22, 2014 6:28 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

Hi Notro! one quick question regarding your framebuffer drivers, as these might be the ones that also profit a lot from this: how do you schedule the block transfer of your frame? I am asking specifically to know: if you are using spi_message->is_dma_mapped what is your maximum frame-size you transf...
by msperl
Fri Feb 07, 2014 1:52 pm
Forum: Camera board
Topic: STICKY: New features for raspistill command
Replies: 106
Views: 116295

Re: New features for raspistill command

P.s: I guess just providing a GPU-api for: * copy a camera image buffer to a second * overlay image-Buffer with a second one (maybe different operations) * Scaling an image buffer * converting the image buffer to JPEG And having pycamera call those APIs would be sufficient to implement everything fr...
by msperl
Fri Feb 07, 2014 1:37 pm
Forum: Camera board
Topic: STICKY: New features for raspistill command
Replies: 106
Views: 116295

Re: New features for raspistill command

Would it be possible to add on overlay image on top of the camera image. It can obviously can get done via imagemagik, but the problem there is the CPU overhead for decompression/modification/recompression of the image. Doing everything inside the GPU should be much faster and then it would be a sin...
by msperl
Tue Feb 04, 2014 10:34 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

I know that flash devices can support dual and quad spi increasing thruput dramatically. Do you have an example of this with a Linux driver? Any device that is supported by the new mtd/spi-NOR driver framework currently under development and which might be in 3.13 or 3.14 already. An example would ...
by msperl
Tue Feb 04, 2014 6:42 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

I know that it might Not be needed, that is why i was asking if there was any need for something like this. I know that flash devices can support dual and quad spi increasing thruput dramatically. But I do not know if this would also apply to LCD display drivers so I was wondering if there were any ...
by msperl
Tue Feb 04, 2014 11:07 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

While thinking about the finer details of the implementation (again) i also came up with the idea that it should be in - principle - be possible to run a separate (single/Dual/quad) SPI bus on the remaining GPIO pins driven only via DMA with minimal CPU involvment. A Quad SPI option would be GPIO 17...
by msperl
Wed Jan 29, 2014 2:57 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

Note that one thing that I came to realize (over the last few days thinking about this project) is the fact that with the DMA implementation it should also be feasible to have more than just 2 ChipSelect lines - in principle ANY GPIO can get used for chip-select and it does not make much of a differ...
by msperl
Wed Jan 29, 2014 2:35 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI driver latency and a possible solution
Replies: 241
Views: 136789

Re: SPI driver latency and a possible solution

No - I am still working on it (if I find some time...)

Go to advanced search