Hi Mark, Christopher, On 26 January 2017 at 01:36, Mark Rutland <mark.rutland@xxxxxxx> wrote: > On Wed, Jan 25, 2017 at 10:38:01AM -0500, Christopher Covington wrote: >> On 01/25/2017 01:46 AM, Fu Wei wrote: >> > On 25 January 2017 at 01:24, Mark Rutland <mark.rutland@xxxxxxx> wrote: >> >> On Wed, Jan 18, 2017 at 09:25:32PM +0800, fu.wei@xxxxxxxxxx wrote: >> >>> From: Fu Wei <fu.wei@xxxxxxxxxx> > >> > And for CNTFRQ(in CNTCTLBase and CNTBaseN) , we can NOT access it in >> > Linux kernel (EL1), >> > Because ARMv8 ARM says: >> > In a system that implements both Secure and Non-secure states, this >> > register is only accessible by Secure accesses. >> > That means we still need to get the frequency of the system counter >> > from CNTFRQ_EL0 in MMIO timer code. >> > This have been proved when I tested this driver on foundation model, I >> > got "0" when I access CNTFRQ from Linux kernel (Non-secure EL1) >> >> That sounds like a firmware problem. Firmware in EL3 is supposed to write >> the value into CNTFRQ. > > Definitely. FW *should* program the CNTFRQ_EL0 CPU registers and any > MMIO CNTFRQ registers. Many thanks for the explanation. This might be the problem. Maybe we can check the UEFI :-) > >> If you're not currently using any firmware, I'd >> recommend the bootwrapper on models/simulators/emulators. >> >> http://git.kernel.org/cgit/linux/kernel/git/mark/boot-wrapper-aarch64.git/tree/arch/aarch64/boot.S#n48 > > Unfortunately, the boot-wrapper only programs the CNTFRQ_EL0 CPU system > registers, and does not program any MMIO CNTFRQ registers. > > IIRC the models it was originally written for didn't have any (and we > had no DT binding until far later...). Luckily the model DTs do not > expose any MMIO timer addresses to the kernel currently. But according to another document(ARMv8-A Foundation Platform User Guide ARM DUI0677K), Table 3-2 ARMv8-A Foundation Platform memory map, we may have two frames in the Generic timer block, right? > > Thanks, > Mark. -- Best regards, Fu Wei Software Engineer Red Hat -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
