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[PATCH 02/25] clock: Add new clock_has_source() function
From: |
Peter Maydell |
Subject: |
[PATCH 02/25] clock: Add new clock_has_source() function |
Date: |
Thu, 21 Jan 2021 19:05:59 +0000 |
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(+)
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
- Re: [PATCH 01/25] ptimer: Add new ptimer_set_period_from_clock() function, (continued)
- [PATCH 12/25] hw/arm/mps2: Inline CMSDK_APB_TIMER creation, Peter Maydell, 2021/01/21
- [PATCH 11/25] hw/arm/armsse: Wire up clocks, Peter Maydell, 2021/01/21
- [PATCH 09/25] hw/watchdog/cmsdk-apb-watchdog: Add Clock input, Peter Maydell, 2021/01/21
- [PATCH 02/25] clock: Add new clock_has_source() function,
Peter Maydell <=
- [PATCH 10/25] hw/arm/armsse: Rename "MAINCLK" property to "MAINCLK_FRQ", Peter Maydell, 2021/01/21
- [PATCH 07/25] hw/timer/cmsdk-apb-timer: Add Clock input, Peter Maydell, 2021/01/21
- [PATCH 13/25] hw/arm/mps2: Create and connect SYSCLK Clock, Peter Maydell, 2021/01/21