From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [Xen-devel] [PATCH v4] xen/arm: Add a clock property To: Stefano Stabellini References: <1468309605-19522-1-git-send-email-dirk.behme@de.bosch.com> <57868CB4.1090504@gmail.com> CC: Dirk Behme , Mark Rutland , , Michael Turquette , Stephen Boyd , Julien Grall , , , From: Dirk Behme Message-ID: <094be367-ff91-aec7-cbd6-cfb8dc711c54@de.bosch.com> Date: Thu, 14 Jul 2016 08:11:16 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed List-ID: 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 >>>> --- >>>> 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 >>>> #include >>>> #include >>>> +#include >>>> #include >>>> #include >>>> #include >>>> @@ -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