Re: [Qemu-devel] [PATCH v2] hw/misc/zynq_slcr: Change CPU clock rate for Linux boots

[Guenter Roeck]

On 09/14/2015 06:17 AM, Nathan Rossi wrote:
> On Mon, Sep 14, 2015 at 10:07 PM, Peter Maydell
> <address@hidden> wrote:
> > On 13 September 2015 at 23:42, Peter Crosthwaite
> > <address@hidden> wrote:
> > > On Sun, Sep 13, 2015 at 1:47 PM, Peter Maydell <address@hidden> wrote:
> > > > On 13 September 2015 at 21:22, Peter Crosthwaite
> > > > <address@hidden> wrote:
> > > > > There may be more changes worth making on is_linux. I don't have the
> > > > > patch with the full list of FSBL-related SLCR changes handy and can't
> > > > > seem to find it in any modern Yocto trees. Wondering if Yocto still
> > > > > supports booting Zynq without FSBL (Nathan/Alistair may know more)?
>
> I have been running QEMU without any patches for zynq in Yocto for
> some time now. I have not experienced the bug mentioned, at least not
> with the kernels I have been testing with. Is this something that is
> more apparent in a 4.2 or newer kernel?

With mainline kernel v4.3-rc1 and qemu v2.4.0-417-g30c38c9, using 
multi_v7_defconfig,
I get

[    0.478288] cpufreq: cpufreq_online: CPU0: Running at unlisted freq: 216666 
KHz
[    0.479378] cpu cpu0: failed to set clock rate: -16
[    0.479515] cpufreq: __target_index: Failed to change cpu frequency: -16
[    0.480107] ------------[ cut here ]------------
[    0.480222] kernel BUG at drivers/cpufreq/cpufreq.c:1287!

with all the upstream devicetree files I am testing with. The crash happens all
the way back to 3.18, so it isn't new either.

Also, with kernel 3.18+, the same version of qemu, and the clock patch applied,
the kernel hangs because it expects the ADC to be supported by the hardware.

Effectively this suggests that you are using a different kernel configuration,
a different devicetree file, and/or an older kernel. I can not do this since the
required configuration and devicetree files change from kernel version to kernel
version, and I test a large range of kernel versions (currently 3.18, 4.1, 4.2,
and mainline, for this platform).

Thanks,
Guenter