Hi,
On Tue, Jul 08, 2008 at 05:14:35PM +0200, Jens Gehrlein wrote:
Wolfgang Denk schrieb:
In message 20080708093022.9272.4677.stgit@tq-sewsrv-4.tq-net.de you wrote:
+/* Timer tick */ +#define CFG_HZ 32768
CFG_HZ is a constant and has to be 1000.
Why is it a board specific define then?
I know, we had a discussion earlier about that issue (see "i.MX31: question about CFG_HZ and CKIL" of 7th May). The situation is as follows:
The TQMA31, as well as the mx32ads use the General Purpose Timer 1, which is feeded by a 32768 clock (possibly imx31_litekit and imx31_phycore with 32000 Hz? I don't know.). The prescale divider can only be an integer. 32768/1000 = non-integer.
The counter is just read. There are no real interrupts (I mention it, because you wrote about this earlier). The origin source code is from U-Boot V2, I suppose. Guennadi used it for the mx31ads.
Not quite correct, I wrote the original mx31 code for U-Boot V1 and then ported it to V2. I think Guennadis work is based on the V1 work.
Currently, I see only one way to solve this:
- Patch the common file cpu/arm1136/mx31/interrupts.c, function
interrupt_init(), so that the prescaler divides by 33. Alternatively, also make the divider a board specific define. 2. Patch all mx31 board config header files with CFG_HZ 1000. 3. All mx31 boards have to be tested.
The following is impossible:
- changing the HW
- using an internal clock, because maximum is 1000 Hz * 4096 = 4096000
Hz (the maximum divider is 4096). All internal clocks are much higher. Please for correction if I'm wrong.
You could add a software divider in get_timer(). But I think it's better to define CFG_HZ to whatever the timer frequency is. At least 49 boards do it.
Regards Sascha