RE: [PATCH 0/2] RTC support for QEMU RISC-V virt machine

[Anup Patel]

> -----Original Message-----
> From: Richard W.M. Jones <address@hidden>
> Sent: Friday, September 27, 2019 5:21 PM
> To: Anup Patel <address@hidden>
> Cc: Palmer Dabbelt <address@hidden>; Alistair Francis
> <address@hidden>; Sagar Karandikar <address@hidden>;
> Bastian Koppelmann <address@hidden>; Atish Patra
> <address@hidden>; address@hidden; qemu-
> address@hidden; Anup Patel <address@hidden>
> Subject: Re: [PATCH 0/2] RTC support for QEMU RISC-V virt machine
> 
> 
> On Tue, Sep 24, 2019 at 08:42:36AM +0000, Anup Patel wrote:
> > This series adds RTC device to QEMU RISC-V virt machine. We have
> > selected Goldfish RTC device model for this. It's a pretty simple
> > synthetic device with few MMIO registers and no dependency external
> > clock. The driver for Goldfish RTC is already available in Linux so we
> > just need to enable it in Kconfig for RISCV and also update Linux
> > defconfigs.
> >
> > We have tested this series with Linux-5.3 plus defconfig changes
> > available in 'goldfish_rtc_v1' branch of:
> > https://github.com/avpatel/linux.git
> 
> Why was this device chosen instead of kvm-clock?

We need a RTC device which worked fine in TCG mode (even without
KVM). The KVMCLOCK is PTP clock which depends on KVM hypercalls.

On ARM virt machine, we have PL031 so instead of that we have
Goldfish RTC on RISC-V virt machine.

Regards,
Anup

> 
> Rich.
> 
> > Anup Patel (2):
> >   hw: timer: Add Goldfish RTC device
> >   riscv: virt: Use Goldfish RTC device
> >
> >  hw/riscv/Kconfig                |   1 +
> >  hw/riscv/virt.c                 |  15 +++
> >  hw/timer/Kconfig                |   3 +
> >  hw/timer/Makefile.objs          |   1 +
> >  hw/timer/goldfish_rtc.c         | 221
> ++++++++++++++++++++++++++++++++
> >  include/hw/riscv/virt.h         |   2 +
> >  include/hw/timer/goldfish_rtc.h |  45 +++++++
> >  7 files changed, 288 insertions(+)
> >  create mode 100644 hw/timer/goldfish_rtc.c  create mode 100644
> > include/hw/timer/goldfish_rtc.h
> >
> > --
> > 2.17.1
> 
> --
> Richard Jones, Virtualization Group, Red Hat
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