Hi,
Am 02.08.2016 um 09:52 schrieb Matthijs van Duin matthijsvanduin@gmail.com:
On 2 August 2016 at 08:45, H. Nikolaus Schaller hns@goldelico.com wrote:
So they should be modified dynamically when switching CPU frequencies?
Yes, and the datasheet seems quite emphatic about it. See section 4.2.1 of the omap5 TRM and the large note at the end of section 4.3.2 (Operating Performance Points -> MPU) of the omap5432 datasheet.
(Random side note: the same restriction apparently applies to AM57xx/DRA7xx based on section 4.2.1 of its TRM, although it's not waved in your face as much as on the omap5.)
Ok, so it is something that should be more fundamentally fixed in the kernel.
Unfortunately I neither have JTAG equipment nor do we have access to the JTAG interface on the Pyra CPU board. Since neither is needed in normal situations. For a big pile of money we could have built some Pyra CPU boards where these signals are made available on external test points.
Ouch. You can get a perfectly adequate JTAG debugger (e.g. XDS100v2) for less than $100, but not having JTAG pinned out is a problem.
Well, having it pinned out is a space/pcb layout problem...
$100 is not the problem and I have an Openmoko Debug board (which is also a JTAG debugger).
The problem is the time to set it up (which software to installation) and learn how to use it appropriately. Like it takes 10 min to buy a pan at some super market... But learning to cook usually needs more time.
I read in the TRM that JTAG can alternatively be muxed to the SD card slot pins (intended for space-constrained applications like smartphones).
Ah yes, I remember. Section 30.2.4 Narrow Interface for Debug and Trace (NIDnT) has some description - but I have not understood how to enable it before boot or if that is done automatically.
So we sould need a NIDnT compatible JTAG probe.
I have no idea however whether that needs any special config other than setting the pinmux.
Interesting idea for someone who wants to volunteer to experiment with that. The setup will be a little tricky since we boot from this SD card but I guess it is doable.