OMAP138L linux user space change MUX settings

Krzysztof Kanas11924

I am trying to do something that I susspect that is impossible.I am using custom Linux on OMAP138L .

I want to access (as read/write) to SYSCFG0 registers from linux user space program. (especialy mux settings). I can access read by mmap() syscal but write operation have no effect. Is it possible to do it from users space program, I think the program should enter Privileged mode which is avalible to linux kernel, is there any way I could accomplish it without writing kernel code (for many reasons I would like to avoid it)

over 15 years ago

0 Sekhar Nori over 15 years ago

TI__Expert 6385 points

Hi,

You can use the program devmem2 (http://buildroot.uclibc.org/downloads/sources/devmem2.c) to access registers from userspace. This program uses mmap call /dev/mem to access memory.

Also, please make sure the SYSCFG module writes are unlocked using KICK registers before attemting a write. Have a look at section 11.5.4 of system reference guide: http://focus.ti.com/lit/ug/sprugm7d/sprugm7d.pdf

Thanks,
Sekhar

0 Krzysztof Kanas11924 over 15 years ago in reply to Sekhar Nori

Intellectual 375 points

I have similar program to get access to that memory (as well kick registers) but as I read, read/write access to that registers have to be done in privileged mode (kernel space in Linux) so if there is easy way to get to kernel context and run some code on ARM - not making any custom changes to the kernel I can only read that values not write to them.

But thanks for answering,

0 Sekhar Nori over 15 years ago in reply to Krzysztof Kanas11924

TI__Expert 6385 points

Right, I did miss the fact that these registers also need the ARM to be in privileged mode. So, a devmem2 based write will not go through. I cant see any other way to do this except to hack the kernel.

Thanks,

Sekhar

0 Aníbal Pinto over 13 years ago in reply to Sekhar Nori

Intellectual 900 points

The issue was resolved ?

I am trying to make a driver to be able to change the pinmux on OMAP L138, a code snippet :

   kick = ioremap(KICK0R, SZ_4K);

   if(WARN(!kick, "Unable to map kick module"))
       return -1;

   printk("Kick value : %x\n", __raw_readl(kick));
   printk("Kick value : %x\n", __raw_writel(0x83E70B13, kick));
   printk("Kick value : %x\n", __raw_writel(0x95A4F1E0, kick + 4));
   printk("Kick 0 value : %x\n", __raw_readl(kick));
   printk("Kick 1 value : %x\n", __raw_readl(kick + 4));

   iounmap(kick);

all the printk return 0x0 ... any idea what can be ?

Thanks

0 Velan over 13 years ago in reply to Aníbal Pinto

TI__Intellectual 2785 points

Hi,

Printk must have loglevel as its first data in format string. I think this could be the problem for getting 0 return values for printk

ex: printk ("<1>Hello Workd\n");

Here "<1>" is the log level

Refer to printk man page for more info.

Best Regards

Velan

0 Aníbal Pinto over 13 years ago in reply to Velan

Intellectual 900 points

I haven't explained me correctly.

The output after execute the code snippet on the mine previous post :

Kick value : 0
Kick value : 0
Kick value : 0
Kick 0 value : 0
Kick 1 value : 0

Any idea why this happens ?

Thanks

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OMAP138L linux user space change MUX settings