rpi3 clock drift

[James Shuriff]

I was looking at the generic_timer.c code and it probes for "arm,armv8-timer" or "arm,armv7-timer". I was thinking of trying to add clock-frequency directly into "timer". ARM MPCore Timecounter is generic_timer.c. That was my next idea, to try copying over some of the binaries from FreeBSD's RPI3 image one at a time to try identifying where the issue is.

My latest build is U-Boot from the git repo with the v2019.10 tag using rpi_3_defconfig with OF_EMBED=n and OF_BOARD=y the former telling U-Boot not to embed the FDT into the binary and the latter informs U-Boot that the FDT will be provided by the board at runtime (start.elf looks for " bcm%d-rpi-%s.dtb"). I get config.txt from /usr/ports/sysutils/rpi-firmware/files/config_rpi3.txt. I build U-Boot with the Clang and ld.lld (which was no small effort!). The binary blobs I get from the Raspberry Pi repository. I build PSCI Monitor from its repo. I get the overlays from the output of my FreeBSD build. I've attached the script I use to build the FAT partition, if you're curious.

- James Shuriff

-----Original Message-----
From: Peter Jeremy <peter at rulingia.com>
Sent: Friday, November 29, 2019 5:03 PM
To: James Shuriff <james at opentech.cc>
Cc: Ian Lepore <ian at freebsd.org>; freebsd-arm at freebsd.org
Subject: Re: rpi3 clock drift

On 2019-Nov-29 20:37:36 +0000, James Shuriff <james at opentech.cc> wrote:
>I dumped the FDT from the system I built from source and I cannot find
>any reference to 0x337F980 (54 MHz). I looked at the FreeBSD source
>file generic_timer.c and it looks like it's grabbing the frequency from
>FDT but I cannot figure out where it's getting the 54 MHz from. clk_osc
>in the FDT is still showing 0x124f800 (19.2 MHz) on the system with the
>bad clock.

I've been rummaging around on my (early) RPi2.  The timer code seems to be the same, even if the SoC is different (I have armv7, RPi3 is armv8).

In my FDT, I have:
        timer {

                compatible = "arm,armv7-timer";
                interrupt-parent = <0x3>;
                interrupts = <0x0 0x1 0x3 0x2>;
                always-on;
        };
There's no clock-frequency clause there and no (obvious) link to:
        clocks {
                compatible = "simple-bus";
                #address-cells = <0x1>;
                #size-cells = <0x0>;
                clock at 3 {
                        compatible = "fixed-clock";
                        reg = <0x3>;
                        #clock-cells = <0x0>;
                        clock-output-names = "osc";
                        clock-frequency = <0x124f800>;
                        phandle = <0x4>;
                };
...
        };

The relevant dmesg should look like:
generic_timer0: <ARMv7 Generic Timer> irq 0,1,2,3 on ofwbus0 Timecounter "ARM MPCore Timecounter" frequency 19200000 Hz quality 1000 Event timer "ARM MPCore Eventtimer" frequency 19200000 Hz quality 1000

At least on my RPi2, I have:
Using DTB provided by EFI at 0x7ff8000.
and

FreeBSD/arm EFI loader, Revision 1.1
   Command line arguments: l
   EFI version: 2.70
   EFI Firmware: Das U-Boot (rev 8216.2304)
   Console: efi (0)
   Load Path: /\efi\boot\bootarm.efi

Are you building a 32-bit or 64-bit FreeBSD?
Where are you getting your boot code from?
Have you tried using the boot code from the FreeBSD RPi3 image with your kernel?

--
Peter Jeremy
________________________________
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