Hello All:

I'm planning to build a new board based on the ATMEL AT91SAM9260 processor, but before doing it so, i would like to confirm several issues, basically what works, and what doesn't work.

SDIO Support:

I would like to integrate a SDIO Wifi module (marvel 8686, atheros or any other SDIO module). I'm unable to find any conclusive information regarding this matter. There are several posts on forums and mailing lists from people trying it and getting only partial success (slow performance, errors, etc).

Question: Is the SDIO stack properly supported on this SoC?
Question: Can somebody confirm if SDIO+WIFI is properly working with this kind of WIFI modules on AT91SAM9260?

GPIO Support:

I'm aware of the existence of a kind of GPIO subsystem on the kernel (linux/gpio.h) documented on "gpio.txt" file. I know i can use /dev/mem to access the hardware registers, but a ready-made API would help a lot.

Questions: Are the GPIO pins on the 9260 integrated on this kernel GPIO subsystem? Or do i have to provide my own GPIO driver to allow user-land applications using GPIO, or just use /dev/mem?


ADC Support:

I would like to be able to use the ADC on the 9260. I've seen several posts on forums using an ADC driver from ATMEL, but again nothing conclusive.

Question: Is this ADC driver available on the mainline kernel or oficially supported by ATMEL?


FLASH Support:

I'm planning to use at least 1GB NAND on my board, but it's difficult to find reference designs using one.
Question: Any warnings here...? Source code reference or something to start with? Problems booting? Do i have to provide a serial dataflash for booting? or the NAND is just enough?

COMPACT FLASH:

Is this SoC (AT91SAM9260) able to totally boot from *JUST* a compact flash? (1st Boot+uboot+kernel+rootfs) NO SPI flash involved...?



Any "BE AWARE OF.."

Some time ago (years) i faced problems with a RM9200 based board having issues with hardware SPI and with lack of support for the RTC, and some others things that consumed lots of time with software work-arounds,etc.. I ended up using a bit-bang driver for the dataflash on those days.

Question: Are there any "erratas" or bad-supported things that must be taken into account before starting the hardware desing of a new board?

Regards,
Jorge.

Hi Jorge,

I know the answers to a couple of your questions, but not all of them. I'm working on a 9G20 board; the 9G20 is pin-compatible with the 9260 and uses most of the same libraries from Atmel.

Regarding GPIO, it is extremely likely that the GPIO driver in the Linux kernel will allow you to control the pins from userspace via sysfs. For example, here's a script I use to initialize pins to work as digital outputs on my board:

for pin in 64 65 66 67 68 69 70 71 72 73 96 97 98 99 100 101
do
echo $pin > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio$pin/direction
done

The gpio.txt file you mentioned has more details.
(Just for reference: http://www.mjmwired.net/kernel/Documentation/gpio.txt)

About the ADC, I'm pretty sure that there is no driver in the kernel yet. The header file is there (I suspect that Atmel just put all the register definitions in the datasheet in headers), but no driver that I'm aware of.

However, there is hope. In 2007, a fellow by the name of Paul Kavan wrote a driver that he posted on this forum (at91.com). It was later picked up by Claudio Mignanti and some other folks, who added some more features and added it into the OpenWRT project a few weeks ago. That code is here: https://dev.openwrt.org/changeset/24814 I just brought that into my kernel yesterday, and at least the sysfs interface seems to work fine. For example:

[root@rascal:/sys/devices/platform/at91_adc]: cat chan0
514

About booting from NAND flash: it can be done. Making it work is straightforward, but making it reliable is tricky. The issue is that NAND flash tends to get a few corrupt bits. This can be corrected by ECC in software, but only if you can load that software. If your bootloader gets corrupted before you can load the ECC code, you're hosed. To combat this, some NAND chips have a section of memory that is guaranteed to be reliable. However, it varies from manufacturer to manufacturer, which makes things complicated.

If it's useful, I've posted my kernel, bootloader, and filesystem on Github: https://github.com/rascalmicro/ and some additional documentation here: http://rascalmicro.com/docs/

Reminder: this is all for the 9G20 chip-- very similar, but not identical.

Good luck,
Brandon

Thank you for your reply Brandon!

To summarize, what we have so far:

- GPIO: Kernel supported, 100% possible.
- ADC: Not kernel supported, but there's available code and it is well tested -> 99% possible.
- NAND BOOT: Possible but pretty dangerous. Fall-back to DATAFLASH+NANDFLASH solution.

About the NAND BOOT: Belive it or not...you have just solved a nightmare for me. I've been asking myself for weeks: "why the censored people use 2 memories (DATAFLASH/NANDFLASH) when using NANDFLASH gives enough capacity for everything and keeps the PCB simple?!?". Again...THANKS! :)

Hi Jorge,

I believe your summary is correct, though I'll repeat again that all my experience is with the 9G20.

One note about dataflash: you are correct that many boards have been designed with NAND flash and dataflash for the reasons you describe. However, I think you'd be better off using a serial flash rather than dataflash. ("Dataflash" refers to chips that are very similar in size and performance to serial flash chips, but which use a slightly different protocol than the SPI used by serial flash chips.)

The bad news is that, so far as I know, Atmel is the only manufacturer of dataflash chips that work with AT91 processors, they're out of stock, and last time I checked the lead-time was 6+ months. For me, that makes the dataflash a chip that should never be used in new designs. In my mind, I try to pretend it doesn't exist.

For serial flash chips, there are 4 or 5 choices of manufacturers supported, including Atmel, Winbond, Macronix, and SST. I think those are a better choice than the Atmel dataflash.

Jorge,

SDIO:
I can confirm at least on the AT91SAM9G20 that the SDIO interface works fine with an SDIO-Wifi module. I am using SDIO Wifi cards from Summit Data Communications, and I have not seen any issues.

GPIO:
As Brandon mentioned, this works nicely using the sysfs interface.

ADC:
I will be looking at this interface in the coming weeks.

FLASH:
I have used both 512Mb and 2 Gb NAND flash memory (Numonyx) with the AT91SAM9G20, and both of these parts work well. No Dataflash is used in the board I am working on. The examples over at linux4sam explain this setup very well.

COMPACT FLASH:
I am very interested to learn what you have learned regarding this interface on the AT91SAM9 processor.

Take care,
-Chris

One problem with the at91sam9260 is that the internal boot code does not support Serial Flash boot. The at91sam9g20 has newer bootcode that does support serial Flash booting. Also the 9260 only has 4k of internal SRAM that can be used for the bootstrap, so that is very limiting in what can be done in the bootstrap.

Hi Jorge

I use board with at91sam9260 processor and 1 GB flash. It's called mmnet1001 from propox, so you can use it as reference. They have quite good documentation even in english:)

I managed to run marvell 88w8688 sdio wifi + bluetooth module on this board. However I had problems running it on 2.6.32 kernel with libertas drivers now It works on marvell drivers from wifi module vendor.

Now I'm scared about nand flash in my devices because I don't use dataflash. I read documentation about used nand MT29F8G08MADWC and there is something that it's with ECC(error correction control) and invalid block mapping.
So does it saves me from errors when reading from this nand?

Hi,

I'm having problems with Marvel 8686 and libertas when I do modeprobe libertas_sdio it doesn't return to prompt.

Looking at the code it's stopping when probing device:

modprobe libertas_sdio.ko helper_name="helper_sd.bin"

drivers/base/dd.c:

if (dev->bus->probe) {
ret = dev->bus->probe(dev); << STOP!
if (ret)
goto probe_failed;
} else if (drv->probe) {

Is there any known problem with libertas and Marvell 8686?

I'm using kernel 2.6.36 and firmware for 8686 sdio: SD-8686-FEDORA26-8.73.7.p3-26340P58.zip and one board with at91sam9g45.