On 2/2/2014 10:34 AM, [email protected] wrote: > Thank you for the reply Charles. That makes sense. The section in the > TRM on the Time-Base submodule, 15.2.2.3, pp 2004 identifies the "CPU > system clock" SYSCLKOUT as the source clock for the submodule. I'll > use your information in my driver and test it with the hardware next > week.
Yes, it can be quite confusing. For example, note (1) on Table 15-41 states: (1) System frequency = SYSCLKOUT, that is, CPU clock. TBCLK = SYSCLKOUT ...but you have to realize each major section of the TRM is written somewhat independently. These document various IP cores that mostly get cut-and-pasted into various SoCs. If this was a Cortex M4 part (which this IP core was likely designed for initially), it probably _would_ be the CPU clock, but in this context they are actually referring to the primary clock for the module, which on the AM335x comes from the L4 interconnect, not from the CPU. Later on, note (1) from Table 15-42 states: (1) System clock, SYSCLKOUT and TBCLK = 100 MHz, 10 ns ...which is much more believable. Of course pretty much all the clock frequencies can be programmed, shut down, and otherwise messed with in complicated ways. Unless you want to crawl through the kernel clock tree code, testing is the easiest way to see what frequency it's really running. Since the maximum supported frequency is 100 MHz, I'd suspect that's what is getting setup by default. -- Charles Steinkuehler [email protected] -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
