[OpenOCD-user] Openocd SWD flash with sysfs or gpiod is too long on Radxa Pi / AMLogic S905Y2

[Maximin C. <max...@gm...>]

Hi everybody,

I was previously using openocd on a RPI Zero 1/2 to flash an STM32F412
using SWD protocol.
The whole flashing operation takes around 5 to 6 seconds which is fine.
My only constraint is that operation takes no more than those 5 to 6
seconds (it is
because the STM32F4 sends keep-alive frames via CAN to the main battery. If
there is
no message received in the last ~7 sec, the battery shutdown and so does
the entiere
system).

Due to the current shortage of RPI boards, I switched to Radxa Pi Zero
(https://wiki.radxa.com/Zero) with an AMLogic S905Y2 inside.
I have tried to use sysfs and gpiod (in my understanding, there are pretty
much the
same thing, and gpiod is newer ?) and despite thoses errors messages:

> Error: Translation from khz to adapter speed not implemented
(maybe it is because of the use of such "generic" layer)

> Error executing event reset-start on target stm32f4x.cpu:
(here I am not sure what is going on...)

it goes to the end, and flash is "correctly" done !

My only (but big !) concern is that with sysfs or gpiod, the flashing
process takes around
9-10sec and as specified in the beginning of this message, this is too
much, and
the system battery goes timeout with this duration...

It is my understanding that the BCM2835gpio driver for OpenOCD uses
specific directs
RAM access to achieve the speed I mesured in my usage (5-6 seconds).
It looks like nothing comparable is available for AMLogic S905Y2/ Radxa Pi ?
I might have no searched deep enough, or in the right place.
If nothing is available, how do you see this ? Should it be straight
forward to
implement ? Can I get at least the same performances I had with the
BCM2835gpio driver ?

Best regards,

-- 
Maximin COSTE