On Thu, 28 Jan 2021 at 14:18, Philippe Mathieu-Daudé <[email protected]> wrote:
>
> On 1/28/21 2:54 PM, Peter Maydell wrote:
> > On Thu, 28 Jan 2021 at 13:47, Bin Meng <[email protected]> wrote:
> >>
> >> On Thu, Jan 28, 2021 at 9:43 PM Peter Maydell <[email protected]>
> >> wrote:
> >>> This retains the CONREG register value for both:
> >>> * 'soft' reset caused by write to device register to disable
> >>> the block
> >>> -- this is corrcet as per the datasheet quote
> >>> * 'power on' reset via TYPE_DEVICE's reset method
> >>> -- but in this case we should reset CONREG, because the Device
> >>> reset method is like a complete device powercycle and should
> >>> return the device state to what it was when QEMU was first
> >>> started.
> >>
> >> The POR value of CONREG is zero, which should be the default value, no?
> >
> > But you're not setting it to zero here, you're leaving it with
> > whatever value it had before. (That's correct for soft reset,
> > but wrong for power-on.)
>
> zero value on power-on is what I tried to describe as
> "It is initialized to zero when the instance is created."
Yes, but QOM device reset does not happen just once at startup and
not thereafter. Consider:
* user starts QEMU
* QOM devices are created and realized
* QOM device reset happens
-- CONREG is zero here because QOM structs are zero-initialized
* guest runs
* guest modifies CONREG from its initial value
* system reset is requested (perhaps by user, perhaps by
guest writing some register or another)
* QOM device reset happens
-- CONREG is not zero here, so reset must clear it
thanks
-- PMM
