From: Dirk Behme <dirk.behme@de.bosch.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
devicetree@vger.kernel.org,
Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@codeaurora.org>,
Dirk Behme <dirk.behme@gmail.com>,
Julien Grall <julien.grall@arm.com>,
xen-devel@lists.xenproject.org, linux-clk@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4] xen/arm: Add a clock property
Date: Thu, 14 Jul 2016 08:11:16 +0200 [thread overview]
Message-ID: <094be367-ff91-aec7-cbd6-cfb8dc711c54__19959.4687241644$1468476773$gmane$org@de.bosch.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1607132002000.26575@sstabellini-ThinkPad-X260>
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@de.bosch.com>
>>>> ---
>>>> 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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next prev parent reply other threads:[~2016-07-14 6:11 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1468309605-19522-1-git-send-email-dirk.behme@de.bosch.com>
2016-07-12 22:26 ` [PATCH v4] xen/arm: Add a clock property Michael Turquette
[not found] ` <146836236759.73491.11707389619985827497@resonance>
2016-07-13 8:35 ` Dirk Behme
[not found] ` <c320f820-8749-f4a4-435e-ddd9379655b5@de.bosch.com>
2016-07-13 18:43 ` Stefano Stabellini
[not found] ` <alpine.DEB.2.10.1607131941200.26575@sstabellini-ThinkPad-X260>
2016-07-13 18:56 ` Dirk Behme
[not found] ` <57868EDE.6060406@gmail.com>
2016-07-13 21:03 ` Michael Turquette
[not found] ` <146844380895.73491.4867379517577413421@resonance>
2016-07-14 6:31 ` Dirk Behme
[not found] ` <7df784ab-d0c0-939b-393e-214535c4b191@de.bosch.com>
2016-07-14 10:14 ` Julien Grall
[not found] ` <57876612.3030407@arm.com>
2016-07-14 10:32 ` Dirk Behme
2016-07-14 10:38 ` Stefano Stabellini
[not found] ` <alpine.DEB.2.10.1607141132000.26575@sstabellini-ThinkPad-X260>
2016-07-14 10:49 ` Dirk Behme
[not found] ` <86951b96-0a3e-79b1-1a2f-88dfeba9b76b@de.bosch.com>
2016-07-14 15:55 ` Stefano Stabellini
[not found] ` <alpine.DEB.2.10.1607141647350.22290@sstabellini-ThinkPad-X260>
2016-07-14 16:30 ` Dirk Behme
[not found] ` <5787BE0B.8060504@gmail.com>
2016-07-14 17:14 ` Julien Grall
[not found] ` <5787C88A.8030103@arm.com>
2016-07-15 7:53 ` Dirk Behme
2016-07-22 0:07 ` Michael Turquette
[not found] ` <146914607316.8780.7961396342647226841@resonance>
2016-07-22 1:16 ` Stefano Stabellini
[not found] ` <alpine.DEB.2.10.1607211804000.6667@sstabellini-ThinkPad-X260>
2016-07-27 5:05 ` Dirk Behme
[not found] ` <dbd46fe5-6f53-d11e-6363-a2c9905d6c8e@gmail.com>
2016-07-28 11:17 ` Julien Grall
[not found] ` <1a486d3b-0dda-d545-ca6a-031a8bf932e9@arm.com>
2016-07-28 14:35 ` Dirk Behme
2016-07-14 10:25 ` Stefano Stabellini
2016-07-13 18:35 ` Stefano Stabellini
[not found] ` <alpine.DEB.2.10.1607131932530.26575@sstabellini-ThinkPad-X260>
2016-07-13 18:47 ` Dirk Behme
[not found] ` <57868CB4.1090504@gmail.com>
2016-07-13 19:07 ` Stefano Stabellini
[not found] ` <alpine.DEB.2.10.1607132002000.26575@sstabellini-ThinkPad-X260>
2016-07-14 6:11 ` Dirk Behme [this message]
[not found] ` <094be367-ff91-aec7-cbd6-cfb8dc711c54@de.bosch.com>
2016-07-14 10:28 ` Stefano Stabellini
2016-07-20 9:43 ` Geert Uytterhoeven
[not found] ` <CAMuHMdU9yP2SMYa5ssrQSu1vwSN2gM4mD-EVYSGr2Pqf=jmCgw@mail.gmail.com>
2016-07-20 11:01 ` Julien Grall
[not found] ` <cc28ef7e-dce3-fe5f-ab80-b662244bcbd0@arm.com>
2016-07-20 11:49 ` Geert Uytterhoeven
[not found] ` <CAMuHMdWeJjcuBHjnjppc5Ys5Ew8VssXzg=dLpLPCOQaBnUo_7Q@mail.gmail.com>
2016-07-20 12:10 ` Julien Grall
[not found] ` <04d9dbfb-196d-a775-7fbb-526aba8085f4@arm.com>
2016-07-20 12:46 ` Geert Uytterhoeven
[not found] ` <CAMuHMdWdqdT4jnae8h9tDDzzh8ZAbJJwiMW-scPBNVwmjYSiWQ@mail.gmail.com>
2016-07-20 12:53 ` Dirk Behme
2016-07-20 13:21 ` Julien Grall
[not found] ` <457c61fd-4a64-b050-cd87-845b7e22ec39@arm.com>
2016-07-22 0:14 ` Michael Turquette
2016-07-12 7:46 Dirk Behme
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