On 02/06/2020 16.53, Stefan Roese wrote:
On 02.06.20 15:29, Rasmus Villemoes wrote:
On 16/03/2020 16.52, Rasmus Villemoes wrote:
On 14/03/2020 13.04, Stefan Roese wrote:
On 13.03.20 17:04, Rasmus Villemoes wrote:
That at least solves half my problems and might be useful to others as well. Then I'll have to figure out the time-stands-still problem in some other way.
If its too hard to enable interrupts in SPL for you or to provide some other means of a working get_timer() API, then we needto find another solution. You started with this weak function, which of course works. What other options are there? Adding a callback mechanism to register platform specific callback functions? Even though this might get a little bit too complicated.
Now that I dig a bit more into this, I seem to remember that we actually also had problems in U-Boot proper when loading a compressed kernel, so for now we're using an uncompressed kernel in our FIT images. I will have to re-investigate, but it now occurs to me that it might be due to the fact that interrupts get disabled during bootm (which makes sense, the same reason I stated previously of interrupt vectors about to be overwritten), so even in U-Boot proper, time as measured by get_timer() ceases to pass after that point, so all the WATCHDOG_RESET() calls from the inflate code effectively get ignored.
So it may be necessary to have some wdt_ratelimit_disable() hook that can be called from bootm_disable_interrupts() and e.g. some board-specific SPL code. I'll do some experiments and figure out if I do indeed need such a hook.
OK, I have now had time to do some more experiments. I have enabled the timer tick in SPL, so get_timer() now "normally" works. Together with the .dts based read of the hardware margin, that makes the watchdog handling mostly work.
But, as I suspected, I do have a problem when loading a compressed kernel image - what I write above "so even in U-Boot proper, time as measured by get_timer() ceases to pass after that point, so all the WATCHDOG_RESET() calls from the inflate code effectively get ignored." is indeed the case.
So, what's the best way to proceed? Should there be a hook disabling the rate-limiting logic that bootm_disable_interrupts() can call? Or must get_timer() always return a sensible result even with interrupts disabled?
Wouldn't it make sense to move the bootm_disable_interrupts() call to after loading and uncompressing the OS image? To right before jumping to the OS?
No, because the point of disabling interrupts is that we may start writing to physical address 0 (e.g. if that's the load= address in the FIT image), which is also where the interrupt vectors reside - i.e., we're about to overwrite 0x900 (the decrementer interrupt vector), so if we don't disable interrupts, we'll crash on the very next decrementer interrupt (i.e., within one millisecond).
Rasmus