From: Dirk Behme <dirk.behme@gmail.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
devicetree@vger.kernel.org, Dirk Behme <dirk.behme@de.bosch.com>,
Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@codeaurora.org>,
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: Wed, 13 Jul 2016 20:47:16 +0200 [thread overview]
Message-ID: <57868CB4.1090504__8745.50320809266$1468435719$gmane$org@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1607131932530.26575@sstabellini-ThinkPad-X260>
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?
We need the xen_node from device tree, anyway.
Best regards
Dirk
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Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-07-13 18:47 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 [this message]
[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
[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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