Why I can't read General Purpose Timer's register value?

Kevin Chow

I am testing the pwm driver with am3517 to control the brightness, and one time I need to read timer11 tclr value. but when insmod it under  kernel 2.6.37 the kernel will crash, but the same procedure will work under kernel 2.6.32.

Technical Reference Manual - AM3517

-------------------------------------------------------------

General-Purpose Timers Register Manual www.ti.com
Table 13-28. TCLR
Address Offset			0x024
Physical Address		0x4831 8024		Instance		GPT1
					0x4903 2024					GPT2
					0x4903 4024					GPT3
					0x4903 6024					GPT4
					0x4903 8024					GPT5
					0x4903 A024					GPT6
					0x4903 C024 					GPT7
					0x4903 E024					GPT8
					0x4904 0024					GPT9
					0x4808 6024					GPT10
					0x4808 8024					GPT11
Description			This register controls optional features specific to the timer functionality.
Type					RW
-----------------------------

My test code:

5531.test_drv.c.txt

the crash log:

8228.insmod-crash-log.txt

over 13 years ago

0 Pankaj Bharadiya over 13 years ago

TI__Expert 5400 points

Hi Kevin,

You need yo enable interface clock before accessing timer module registers.

Please make sure that interface clock is enabled.

Regards,

Pankaj Bharadiya

0 Kevin Chow over 13 years ago in reply to Pankaj Bharadiya

Expert 1625 points

Hi Pankaj,

Thiis time I add the clk_enable code to my test driver, my code is

5047.test_drv.c.txt

and the error is still the same, did I enable the clock wrongly? the log is

4540.enable-fclk-log.txt

Thanks,

Kevin

0 Pankaj Bharadiya over 13 years ago in reply to Kevin Chow

TI__Expert 5400 points

Hi Kevin,

Please enable both functional and interface clock for GPT11.

You can use devmem2 to enable and test.

Here is what I have tried on AM37x board.

1. Enable Functional clock. <Bit 12 , CM_FCLKEN1_CORE register >

# devmem2 0x48004a00 w
/dev/mem opened.
Memory mapped at address 0x40120000.
Value at address 0x48004A00 (0x40120a00): 0x6000

# devmem2 0x48004a00 w 0x7000

2. Enable Interface clock (BIT 12: CM_ICLKEN1_CORE register)

# devmem2 0x48004a10 w
/dev/mem opened.
Memory mapped at address 0x4013e000.
Value at address 0x48004A10 (0x4013ea10): 0x303E052

# devmem2 0x48004a10 w 0x303F052
/dev/mem opened.
Memory mapped at address 0x40223000.
Value at address 0x48004A10 (0x40223a10): 0x303E052
Written 0x303F052; readback 0x303F052

3. Test GPT11 Read using devmem2

# devmem2 0x48088024 w
/dev/mem opened.
Memory mapped at address 0x40061000.
Value at address 0x48088024 (0x40061024): 0x0

# lsmod
wl12xx 125411 0 - Live 0xbf0b1000
mac80211 191033 1 wl12xx, Live 0xbf071000
omaplfb 10798 0 - Live 0xbf069000
cfg80211 134778 2 wl12xx,mac80211, Live 0xbf038000
pvrsrvkm 154142 31 omaplfb, Live 0xbf007000
compat 3717 1 mac80211, Live 0xbf000000

4. Load your module (Commented clock code as clocks are enabled using devmem2 utility)

# insmod test.ko
[ 385.462005] -----------------test_drv_init-enable clk--------------------
[ 385.469146] virt_base = fa088000
[ 385.472503] tclr = 21

Reards,

Pankaj Bharadiya

0 HONGSEN LI over 13 years ago in reply to Pankaj Bharadiya

Intellectual 295 points

I want to generate pulses on GPTimer11. But I am not able to generate it. could you give me an example ,many thanks

0 Davi Turvene over 13 years ago in reply to Pankaj Bharadiya

Prodigy 10 points

@Pankaj

Thanks! Great explanation and (finally) made me read the PRCM chapter of the reference manual. Now I understand the need for the functional and interface clocks.

Dave

0 Abhishek Gupta95209 over 13 years ago in reply to Pankaj Bharadiya

Prodigy 40 points

Hello Pankaj

I was trying to boot an elf image through kexec(without uboot) on BeagleBoard xM(omap 3530).

During booting process, a function is used to intialize timer which tries to use GPTIMER 11 registers

and when it tries to access registers an error message comes (KERNEL DATA ABORT!).

It will be very helpful if you could help.

Urgent

0 Pankaj Bharadiya over 13 years ago in reply to Abhishek Gupta95209

TI__Expert 5400 points

HI Abhishek,

Please do GPT11 inferface clock and functional clock from your board file and try

Please send boot log to debug this further.

Regards,

Pankaj Bharadiya

0 Abhishek Gupta95209 over 13 years ago in reply to Pankaj Bharadiya

Prodigy 40 points

Hi Pankaj

I am trying boot secure embedded L4 thorough kexec(without uboot).

The elf image does have a elfloader which enables mmu, paging etc.

which then loads kernel image.

This is the message I am getting while booting on BeagleBoard xM:

# kexec -l wombat-image-arm-omap3
In ELF ARM PROBE[   36.734741] Start Address = 0x82000110

In ARM ELF LOAD
# kexec -e
[   40.768890] Starting new kernel
[   40.772308] Start Address = 82000110
[   40.776062] Bye!
ELF-loader image started:   paddr=[0x82000110..0x82754000]
ELF-loading kernel image:   paddr=[0x80000000..0x8002c000] vaddr=[0xf0000000..0xf002c000] v_entry=0xf0002f9c
ELF-loading userland image: paddr=[0x80cff000..0x814f5000] vaddr=[0x009ff000..0x011f5000] v_entry=0x00a00000
Enabling MMU and paging
Jumping to kernel-image entry point
Bootstrapping kernel

KERNEL DATA ABORT!
Faulting instruction: 0xf0000170
DSFR: 0x1008
FAR: 0xfff03014 DFSR: 0x1008
halting...

This is the function which when called produces an error:

init_timer(void)
{
    int timeout;

    timer->cfg = TIOCP_CFG_SOFTRESET;

    for(timeout = 10000; !timer->tistat && timeout > 0; timeout--)
        ;
    if(!timeout)
        return;

    maskInterrupt(/*disable*/ true, GPTIMER11_IRQ);

    // Set the reload value
    timer->tldr = 0xFFFFFFFFUL - TIMER_INTERVAL_TICKS;

    // Enables interrupt on overflow
    timer->tier = TIER_OVERFLOWENABLE;

    // Clear the read register
    timer->tcrr = 0xFFFFFFFFUL - TIMER_INTERVAL_TICKS;

    // Set autoreload and start the timer
    timer->tclr = TCLR_AUTORELOAD | TCLR_STARTTIMER;
}

0 Abhishek Gupta95209 over 13 years ago in reply to Abhishek Gupta95209

Prodigy 40 points

timer->cfg = TIOCP_CFG_SOFTRESET; // This one working

for(timeout = 10000; !timer->tistat && timeout > 0; timeout--) // not able to read timer->tistat

0 Vineet Prakash Singh over 12 years ago in reply to Davi Turvene

Prodigy 240 points

hii pankaj

can you tell me which refrence manual you referred, i am also going to start with timers.

thanx

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Why I can't read General Purpose Timer's register value?