iMx25 harware register

[simonl]

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

bl

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

[simonl]

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

[simonl]

Ok thank's, I have misunderstood.

[igorpadykov]

Hi Simon

AIPS chapter is not present in RM, you can

obtain it creating service request

Best regards

igor

[simonl]

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

[simonl]

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.

[igorpadykov · Accepted solution]

Hi Simon

this may be related with AIPS priviledge settings,

suggest to create service request for obtaining

AIPS description.

Best regards

igor

[igorpadykov]

Hi Simon

register may be not accessible when module clock is gated

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

Best regards

igor

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