Re: [PATCH 7/7] hw/watchdog/wdt_aspeed: Reduce timer precision to micro-second

[Andrew Jeffery]

On Wed, 17 Jun 2020, at 13:11, Philippe Mathieu-Daudé wrote:
> Hi Andrew,
> 
> On 6/17/20 3:18 AM, Andrew Jeffery wrote:
> > On Tue, 16 Jun 2020, at 17:21, Philippe Mathieu-Daudé wrote:
> >> The current implementation uses nano-second precision, while
> >> the watchdog can not be more precise than a micro-second.
> > 
> > What's the basis for this assertion? It's true for the AST2500 and AST2600, 
> > but 
> > the AST2400 can run the watchdog from either a 1MHz clock source or the APB 
> > clock (which must be at least 16.5MHz on palmetto). The reset state on the
> > AST2400 configures the watchdog for the APB clock rate.
> > 
> > The Linux driver will eventually configure the watchdog for 1MHz mode
> > regardless so perhaps the AST2400 reset state is a bit of a corner case, but
> > I feel the assertion should be watered down a bit?
> 
> What about this description?
> 
> "The current implementation uses nano-second precision, but
>  is not more precise than micro-second precision.
>  Simplify by using a micro-second based timer.
>  Rename the timer 'timer_us' to have the unit explicit."

So is this a limitation of QEMUTimer? I was establishing that the hardware can 
operate at greater than 1 micro-second precision.

Andrew