I finally got back to looking at this issue and re-read the TI processor document regarding the "Control Module" in the am3359. Apparently the registers in the Control Module can only be written in processor privileged mode and my process would be running in user mode. How can a mechanism be created in Genode to write to such registers?
Bob Stewart
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On October 24, 2013 12:20:16 PM Bob Stewart <robjsstewart@...196...> wrote:
Understand what you mean now, Christian. The registers I'm working with are read by the processor to determine what mode the gpio pins will run in (amongst other things), so once set they should be readable. I'll do some testing with hardware to see if the mode changes are really taking effect. On this hardware there are eight modes per pin and, depending on the mode, the pin might simply be digital level or it might output a PWM signal. So mode setting is important.
I pulled the "decaprox" branch from ksyslabs repository. That branch has a driver for am33xx gpio. I moved the changes for the am33xx gpio into my local copy of 13.08 along with test stubs. All that worked ok and I could get gpio pins to function as I wanted. The gpio driver does not however have functionality to set the pin modes and one is stuck with pins in the mode the boot rom sets.
Bob
On October 24, 2013 11:30:46 AM Christian Helmuth <christian.helmuth@...1...> wrote:
Hej,
On Thu, Oct 24, 2013 at 11:20:09AM -0400, Bob Stewart wrote:
Thanks for the reply Christian. If I'm writing to a local memory
location why would the change in value not show in the debugger, even if that location is memory mapped to a hardware register?
From my experience this heavily depends on the device behind the "memory location" as this is not RAM. The device may, for example, interpret bit 0 set on write as "clear register", which would gain you 0x0 on writing 0x1. Note, it was just a plain guess as I do not know your platform or device very well.
BTW, which Ksyslabs repository and branch did you base your work on? Does it already include a GPIO driver for your BeagleBone?
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