| Message ID | 20210121190622.22000-3-peter.maydell@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Convert CMSDK timer, watchdog, dualtimer to Clock framework | expand |
On 19:05 Thu 21 Jan , Peter Maydell wrote: > Add a function for checking whether a clock has a source. This is > useful for devices which have input clocks that must be wired up by > the board as it allows them to fail in realize rather than ploughing > on with a zero-period clock. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Luc Michel <luc@lmichel.fr> > --- > docs/devel/clocks.rst | 16 ++++++++++++++++ > include/hw/clock.h | 15 +++++++++++++++ > 2 files changed, 31 insertions(+) > > diff --git a/docs/devel/clocks.rst b/docs/devel/clocks.rst > index 2548d842322..c54bbb82409 100644 > --- a/docs/devel/clocks.rst > +++ b/docs/devel/clocks.rst > @@ -235,6 +235,22 @@ object during device instance init. For example: > /* set initial value to 10ns / 100MHz */ > clock_set_ns(clk, 10); > > +To enforce that the clock is wired up by the board code, you can > +call ``clock_has_source()`` in your device's realize method: > + > +.. code-block:: c > + > + if (!clock_has_source(s->clk)) { > + error_setg(errp, "MyDevice: clk input must be connected"); > + return; > + } > + > +Note that this only checks that the clock has been wired up; it is > +still possible that the output clock connected to it is disabled > +or has not yet been configured, in which case the period will be > +zero. You should use the clock callback to find out when the clock > +period changes. > + > Fetching clock frequency/period > ------------------------------- > > diff --git a/include/hw/clock.h b/include/hw/clock.h > index 6382f346569..e5f45e2626d 100644 > --- a/include/hw/clock.h > +++ b/include/hw/clock.h > @@ -139,6 +139,21 @@ void clock_clear_callback(Clock *clk); > */ > void clock_set_source(Clock *clk, Clock *src); > > +/** > + * clock_has_source: > + * @clk: the clock > + * > + * Returns true if the clock has a source clock connected to it. > + * This is useful for devices which have input clocks which must > + * be connected by the board/SoC code which creates them. The > + * device code can use this to check in its realize method that > + * the clock has been connected. > + */ > +static inline bool clock_has_source(const Clock *clk) > +{ > + return clk->source != NULL; > +} > + > /** > * clock_set: > * @clk: the clock to initialize. > -- > 2.20.1 > --
On 1/21/21 8:05 PM, Peter Maydell wrote: > Add a function for checking whether a clock has a source. This is > useful for devices which have input clocks that must be wired up by > the board as it allows them to fail in realize rather than ploughing > on with a zero-period clock. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > docs/devel/clocks.rst | 16 ++++++++++++++++ > include/hw/clock.h | 15 +++++++++++++++ > 2 files changed, 31 insertions(+) Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
diff --git a/docs/devel/clocks.rst b/docs/devel/clocks.rst index 2548d842322..c54bbb82409 100644 --- a/docs/devel/clocks.rst +++ b/docs/devel/clocks.rst @@ -235,6 +235,22 @@ object during device instance init. For example: /* set initial value to 10ns / 100MHz */ clock_set_ns(clk, 10); +To enforce that the clock is wired up by the board code, you can +call ``clock_has_source()`` in your device's realize method: + +.. code-block:: c + + if (!clock_has_source(s->clk)) { + error_setg(errp, "MyDevice: clk input must be connected"); + return; + } + +Note that this only checks that the clock has been wired up; it is +still possible that the output clock connected to it is disabled +or has not yet been configured, in which case the period will be +zero. You should use the clock callback to find out when the clock +period changes. + Fetching clock frequency/period ------------------------------- diff --git a/include/hw/clock.h b/include/hw/clock.h index 6382f346569..e5f45e2626d 100644 --- a/include/hw/clock.h +++ b/include/hw/clock.h @@ -139,6 +139,21 @@ void clock_clear_callback(Clock *clk); */ void clock_set_source(Clock *clk, Clock *src); +/** + * clock_has_source: + * @clk: the clock + * + * Returns true if the clock has a source clock connected to it. + * This is useful for devices which have input clocks which must + * be connected by the board/SoC code which creates them. The + * device code can use this to check in its realize method that + * the clock has been connected. + */ +static inline bool clock_has_source(const Clock *clk) +{ + return clk->source != NULL; +} + /** * clock_set: * @clk: the clock to initialize.
Add a function for checking whether a clock has a source. This is useful for devices which have input clocks that must be wired up by the board as it allows them to fail in realize rather than ploughing on with a zero-period clock. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- docs/devel/clocks.rst | 16 ++++++++++++++++ include/hw/clock.h | 15 +++++++++++++++ 2 files changed, 31 insertions(+) -- 2.20.1