On 13.07.2016 21:07, Stefano Stabellini wrote:
On Wed, 13 Jul 2016, Dirk Behme wrote:
On 13.07.2016 20:35, Stefano Stabellini wrote:
On Tue, 12 Jul 2016, Dirk Behme wrote:
Clocks described by this property are reserved for use by Xen, and the OS
must not alter their state any way, such as disabling or gating a clock,
or modifying its rate. Ensuring this may impose constraints on parent
clocks or other resources used by the clock tree.
This property is used to proxy clocks for devices Xen has taken ownership
of, such as UARTs, for which the associated clock controller(s) remain
under the control of Dom0.
Up to now, the workaround for this has been to use the Linux kernel
command line parameter 'clk_ignore_unused'. See Xen bug
http://bugs.xenproject.org/xen/bug/45
too.
Signed-off-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
---
Changes in v4: Switch to the xen.txt description proposed by Mark:
https://www.spinics.net/lists/arm-kernel/msg516158.html
Changes in v3: Use the xen.txt description proposed by Michael. Thanks!
Changes in v2: Drop the Linux implementation details like
clk_disable_unused
in xen.txt.
Documentation/devicetree/bindings/arm/xen.txt | 12 +++++++
arch/arm/xen/enlighten.c | 47
+++++++++++++++++++++++++++
2 files changed, 59 insertions(+)
diff --git a/Documentation/devicetree/bindings/arm/xen.txt
b/Documentation/devicetree/bindings/arm/xen.txt
index c9b9321..437e50b 100644
--- a/Documentation/devicetree/bindings/arm/xen.txt
+++ b/Documentation/devicetree/bindings/arm/xen.txt
@@ -17,6 +17,18 @@ the following properties:
A GIC node is also required.
This property is unnecessary when booting Dom0 using ACPI.
+Optional properties:
+
+- clocks: a list of phandle + clock-specifier pairs
+ Clocks described by this property are reserved for use by Xen, and the
+ OS must not alter their state any way, such as disabling or gating a
+ clock, or modifying its rate. Ensuring this may impose constraints on
+ parent clocks or other resources used by the clock tree.
+
+ Note: this property is used to proxy clocks for devices Xen has taken
+ ownership of, such as UARTs, for which the associated clock
+ controller(s) remain under the control of Dom0.
+
To support UEFI on Xen ARM virtual platforms, Xen populates the FDT
"uefi" node
under /hypervisor with following parameters:
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 47acb36..5c546d0 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -24,6 +24,7 @@
#include <linux/of_fdt.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>
+#include <linux/clk-provider.h>
#include <linux/cpuidle.h>
#include <linux/cpufreq.h>
#include <linux/cpu.h>
@@ -444,6 +445,52 @@ static int __init xen_pm_init(void)
}
late_initcall(xen_pm_init);
+/*
+ * Check if we want to register some clocks, that they
+ * are not freed because unused by clk_disable_unused().
+ * E.g. the serial console clock.
+ */
+static int __init xen_arm_register_clks(void)
+{
+ struct clk *clk;
+ struct device_node *xen_node;
+ unsigned int i, count;
+ int ret = 0;
+
+ xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
+ if (!xen_node) {
+ pr_err("Xen support was detected before, but it has
disappeared\n");
+ return -EINVAL;
+ }
Given that this is a late initcall, the following should work:
if (!xen_domain())
return -ENODEV;
Hmm, sorry, "should work" for what?
As a Xen check, if (!xen_domain()) is the common pattern.
We need the xen_node from device tree, anyway.
In that case, what don't you just use the global xen_node in this file?
With the recent code there is no global xen_node any more:
https://lists.xen.org/archives/html/xen-devel/2016-06/msg02878.html
-- cut --
The code in this file has changed quite a lot with the support of ACPI.
For instance "xen_node" is not anymore a global variable. Can you rebase
your rework on top of the branch for-linus-4.8?
You can find the branch in:
git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git
-- cut --
Best regards
Dirk
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