i.MX ProcessorsのトピックRe: iMx25 harware register

iMx25 harware register

simonl — Wed, 01 Jun 2016 13:47:32 GMT

Hi,
I'm running bare metal on iMx25 PDK with debug board.
I'm trying to access UART register (USR1) on user mode but each time it raise a data abort.
Is hardware register only accessible from privileged mode ?

Documentation says I can read/write as user, may be I miss to configure a register but i don't know which one.

This is the exemple code I made to read USR1 at the boot.

start_boot:

// After a reset, the mode is ARM, Supervisor, interrupts disabled.

// Invalidate both ICache and DCache : not done upon emulator reset

ldr r1,=0

mcr p15,0,r1,c7,c7,0

// Disable MMU translation, D cache and enable I cache

mrc p15,0,r1,c1,c0,0

ldr r0,=CP_DIS_MASK // 0xFFFFEFFA

and r1,r1,r0

orr r1,r1,#(1<<12)

orr r1,r1,#2

mcr p15,0,r1,c1,c0,0

// Initialize clocks

low_level_init

// Switch to user and try access USR1

bic r0,r0,#MODE_MSK // Clear the mode bits

orr r0,r0,#USR_MODE // Set USER mode bits

msr cpsr_c,r0

ldr r3, =0x43f90098

ldr r3,[r3]

If you have any idea why I can't access uart register in user mode, any help is welcome.

Thanks in advance.

Simon

Re: iMx25 harware register

igorpadykov — Thu, 02 Jun 2016 00:43:15 GMT

Hi Simon

in CCM, so one can check uart bits in CGCRx registers.

Best regards

igor

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Re: iMx25 harware register

simonl — Mon, 06 Jun 2016 10:08:10 GMT

Hi Igor
I tried with module clock enabled and disabled for my Uart but I have always the same problem.
When I'm tring to access Uart register in privileged mode, in the same terms it's working.
I thing I have a permission access problem.

I check all my config and none register seems to enable a module which manage access permisson.
So I don't know where problem come from. May be from boot.
I load my program in RAM direclty with JTAG and configure the iMx25 PDK to boot on SD Card.

Re: iMx25 harware register

igorpadykov — Mon, 06 Jun 2016 12:30:12 GMT

Hi Simon

this may be related with AIPS priviledge settings,

suggest to create service request for obtaining

AIPS description.

Best regards

igor

Re: iMx25 harware register

simonl — Mon, 13 Jun 2016 14:08:52 GMT

Hi Igor,
Sorry for the wait,

I didn't found much information about AIPS registers in the iMx25 doc.
The AIPS A configuration seems to be made by MAX module.
I looked at my MAX description, but it seems good, all access restriction are disabled ...

Best regards

Simon

Re: iMx25 harware register

igorpadykov — Tue, 14 Jun 2016 00:44:44 GMT

Hi Simon

AIPS chapter is not present in RM, you can

obtain it creating service request

Best regards

igor

Re: iMx25 harware register

simonl — Tue, 14 Jun 2016 06:57:22 GMT

Ok thank's, I have misunderstood.

Re: iMx25 harware register

simonl — Tue, 14 Jun 2016 13:36:06 GMT

You solve my problem. Thank's a lot igor !