Re: [Qemu-devel] [PATCH] hw/char/cmsdk-apb-timer: Correctly identify and set one-shot mode

[Guenter Roeck <linux@roeck-us.net>]

On Tue, Jul 03, 2018 at 06:06:24PM +0100, Peter Maydell wrote:
> On 2 July 2018 at 19:37, Guenter Roeck <linux@roeck-us.net> wrote:
> > Please try http://server.roeck-us.net/qemu/an385/
> >
> > vmlinux is plain v4.18-rc3 compiled with the provided defconfig and
> > the provided toolchain (position independent, created with buildroot).
> > defconfig is mps2_defconfig+CONFIG_BLK_DEV_INITRD=y. Older kernels work
> > as well (I tested as far back as 4.9.y), with the same configuration.
> >
> > qemu is from the master-local branch in my repository, built with
> > https://github.com/groeck/linux-build-test/blob/master/qemu/buildall.sh.
> >
> > The boot wrapper was generated from
> > https://github.com/groeck/linux-build-test/tree/master/rootfs/arm/arm-m3-bootwrapper/.
> >
> > run.sh should boot the system into a shell (at least it does for me).
> 
> Thanks. Unfortunately I tried running that a bunch of times with a
> version of your QEMU with the 'set one-shot mode' patch reverted,
> and it still booted every time.
> 

Oddly enough, I now seem to be unable to reproduce the problem either.
Weird, when I wrote the patch it was absolutely necessary.

The only other change I can think of would be the code to set the
serial baud rate in the boot loader, which I did not have initially.
Is it possible that the hangup could have been caused by that ? 

Is it worth tracking it down, or are we ok ?

> However, I think I agree with you that it's better for the timer
> device to avoid doing things that result in the ptimer code emitting
> warnings rather than just dropping the ptimer warning, so I'm going
> to take this patch upstream.
> 
> I also sorted through some of the other corner case issues
> (eg restarting a stopped one-shot timer by writing to VALUE,
> and whether an interrupt should be generated if VALUE is
> written as zero). I'm going to send a patchset in a moment that
> includes this patch and those fixes. I've tested that set by
> applying it to your master-local/ branch and using your testcase
> here, as well as by using my buildroot/uclinux image on an
> upstream QEMU (and a few other RTOS images I had to hand).
> 

The series WFM as well. I'll send out a Tested-by: in a minute.

Thanks,
Guenter