[PATCH] clk: add option to keep boot clocks on

This is primarily useful when there's a driver that doesn't claim clocks
properly, but the bootloader does. It's not expected to be used in normal
cases, but for bringup and debug it's very useful to have the option to
not gate unclaimed clocks that are still on.

Signed-off-by: Olof Johansson <redacted>
---

Mike, this is a pretty trivial patch that I would love to see in 3.10
even though it's getting late. I'm definitely not picky about the naming
of the boot option, so feel free to change it.


-Olof

 drivers/clk/clk.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 20ce67f..b22551e 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c

@@ -499,10 +499,24 @@ out:
 	return;
 }
 
+
+static bool keep_boot_clocks;
+static int __init clk_keep_boot_clocks(char *__unused)
+{
+	keep_boot_clocks = true;
+	return 1;
+}
+__setup("clk_keep_boot_clocks", clk_keep_boot_clocks);
+
 static int clk_disable_unused(void)
 {
 	struct clk *clk;
 
+	if (keep_boot_clocks) {
+		pr_warn("clk: Not disabling unused clocks\n");
+		return 0;
+	}
+
 	clk_prepare_lock();
 
 	hlist_for_each_entry(clk, &clk_root_list, child_node)

-- 
1.8.1.192.gc4361b8

On 04/26/13 16:39, Olof Johansson wrote:

This is primarily useful when there's a driver that doesn't claim clocks
properly, but the bootloader does. It's not expected to be used in normal
cases, but for bringup and debug it's very useful to have the option to
not gate unclaimed clocks that are still on.

Signed-off-by: Olof Johansson <redacted>

add to Documentation/kernel-parameters.txt or somewhere else?

-- 
~Randy

On Fri, Apr 26, 2013 at 5:08 PM, Randy Dunlap [off-list ref] wrote:

On 04/26/13 16:39, Olof Johansson wrote:

quoted

This is primarily useful when there's a driver that doesn't claim clocks
properly, but the bootloader does. It's not expected to be used in normal
cases, but for bringup and debug it's very useful to have the option to
not gate unclaimed clocks that are still on.

Signed-off-by: Olof Johansson <redacted>

add to Documentation/kernel-parameters.txt or somewhere else?

Ah, yes, of course. I'll wait for Mike to provide input on the color
of the shed, since it might change location in the file if it's
renamed. And then repost with documentation update.


-Olof

Quoting Olof Johansson (2013-04-26 16:39:51)

This is primarily useful when there's a driver that doesn't claim clocks
properly, but the bootloader does. It's not expected to be used in normal
cases, but for bringup and debug it's very useful to have the option to
not gate unclaimed clocks that are still on.

Signed-off-by: Olof Johansson <redacted>
---

Mike, this is a pretty trivial patch that I would love to see in 3.10
even though it's getting late. I'm definitely not picky about the naming
of the boot option, so feel free to change it.

This bike shed could be improved with a different color of paint.
Opinions below:

Remove extra whitespace.

+static bool keep_boot_clocks;
+static int __init clk_keep_boot_clocks(char *__unused)
+{
+       keep_boot_clocks = true;
+       return 1;
+}
+__setup("clk_keep_boot_clocks", clk_keep_boot_clocks);

s/clk_keep_boot_clocks/clk_ignore_unused/

This matches nicely with the existing CLK_IGNORE_UNUSED flag in
include/linux/clk-provider.h

In addition to Randy's suggestion to update kernel-parameters.txt,
please also toss in a note somewhere in Documentation/clk.txt so that
others bringing up new platforms can more easily find out about this
boot option.  Don't worry about making it pretty since I plan to rework
the clock documentation for 3.11.

Otherwise patch looks good to me.  I did some testing and I would be
comfortable sneaking this in for 3.10.

Regards,
Mike

+
 static int clk_disable_unused(void)
 {
        struct clk *clk;
 
+       if (keep_boot_clocks) {
+               pr_warn("clk: Not disabling unused clocks\n");
+               return 0;
+       }
+
        clk_prepare_lock();
 
        hlist_for_each_entry(clk, &clk_root_list, child_node)
-- 
1.8.1.192.gc4361b8

On Sat, Apr 27, 2013 at 11:17:13AM -0700, Mike Turquette wrote:

Quoting Olof Johansson (2013-04-26 16:39:51)

quoted

This is primarily useful when there's a driver that doesn't claim clocks
properly, but the bootloader does. It's not expected to be used in normal
cases, but for bringup and debug it's very useful to have the option to
not gate unclaimed clocks that are still on.

Signed-off-by: Olof Johansson <redacted>
---

Mike, this is a pretty trivial patch that I would love to see in 3.10
even though it's getting late. I'm definitely not picky about the naming
of the boot option, so feel free to change it.

This bike shed could be improved with a different color of paint.
Opinions below:

quoted

-Olof

 drivers/clk/clk.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 20ce67f..b22551e 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c

@@ -499,10 +499,24 @@ out:
        return;
 }
 
+

Remove extra whitespace.

quoted

+static bool keep_boot_clocks;
+static int __init clk_keep_boot_clocks(char *__unused)
+{
+       keep_boot_clocks = true;
+       return 1;
+}
+__setup("clk_keep_boot_clocks", clk_keep_boot_clocks);

s/clk_keep_boot_clocks/clk_ignore_unused/

This matches nicely with the existing CLK_IGNORE_UNUSED flag in
include/linux/clk-provider.h

In addition to Randy's suggestion to update kernel-parameters.txt,
please also toss in a note somewhere in Documentation/clk.txt so that
others bringing up new platforms can more easily find out about this
boot option.  Don't worry about making it pretty since I plan to rework
the clock documentation for 3.11.

Otherwise patch looks good to me.  I did some testing and I would be
comfortable sneaking this in for 3.10.

Great, thanks. I'm happy to paint in any color requested. :)

V2 patch posted separately.


-Olof

This is primarily useful when there's a driver that doesn't claim clocks
properly, but the bootloader leaves them on. It's not expected to be used
in normal cases, but for bringup and debug it's very useful to have the
option to not gate unclaimed clocks that are still on.

Signed-off-by: Olof Johansson <redacted>
---
 Documentation/clk.txt               | 11 +++++++++++
 Documentation/kernel-parameters.txt |  8 ++++++++
 drivers/clk/clk.c                   | 13 +++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/Documentation/clk.txt b/Documentation/clk.txt
index 4274a54..b9911c2 100644
--- a/Documentation/clk.txt
+++ b/Documentation/clk.txt

@@ -231,3 +231,14 @@ To better enforce this policy, always follow this simple rule: any
 statically initialized clock data MUST be defined in a separate file
 from the logic that implements its ops.  Basically separate the logic
 from the data and all is well.
+
+	Part 6 - Disabling clock gating of unused clocks
+
+Sometimes during development it can be useful to be able to bypass the
+default disabling of unused clocks. For example, if drivers aren't enabling
+clocks properly but rely on them being on from the bootloader, bypassing
+the disabling means that the driver will remain functional while the issues
+are sorted out.
+
+To bypass this disabling, include "clk_ignore_unused" in the bootargs to the
+kernel.

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index c4fa000..c3bfacb 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt

@@ -44,6 +44,7 @@ parameter is applicable:
 	AVR32	AVR32 architecture is enabled.
 	AX25	Appropriate AX.25 support is enabled.
 	BLACKFIN Blackfin architecture is enabled.
+	CLK	Common clock infrastructure is enabled.
 	CMA	Contiguous Memory Area support is enabled.
 	DRM	Direct Rendering Management support is enabled.
 	DYNAMIC_DEBUG Build in debug messages and enable them at runtime

@@ -473,6 +474,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	cio_ignore=	[S390]
 			See Documentation/s390/CommonIO for details.
+	clk_ignore_unused
+			[CLK]
+			Keep all clocks already enabled by bootloader on,
+			even if no driver has claimed them. This is useful
+			for debug and development, but should not be
+			needed on a platform with proper driver support.
+			For more information, see Documentation/clk.txt.
 
 	clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
 			[Deprecated]

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 20ce67f..934cfd1 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c

@@ -499,10 +499,23 @@ out:
 	return;
 }
 
+static bool clk_ignore_unused;
+static int __init clk_ignore_unused_setup(char *__unused)
+{
+	clk_ignore_unused = true;
+	return 1;
+}
+__setup("clk_ignore_unused", clk_ignore_unused_setup);
+
 static int clk_disable_unused(void)
 {
 	struct clk *clk;
 
+	if (clk_ignore_unused) {
+		pr_warn("clk: Not disabling unused clocks\n");
+		return 0;
+	}
+
 	clk_prepare_lock();
 
 	hlist_for_each_entry(clk, &clk_root_list, child_node)

-- 
1.8.1.192.gc4361b8

Quoting Olof Johansson (2013-04-27 14:10:18)

This is primarily useful when there's a driver that doesn't claim clocks
properly, but the bootloader leaves them on. It's not expected to be used
in normal cases, but for bringup and debug it's very useful to have the
option to not gate unclaimed clocks that are still on.

Signed-off-by: Olof Johansson <redacted>

Thanks for the respin.  I had to fix up a trivial merge issue with
Documentation/kernel-parameters.txt, but no big deal.  Patch is merged
into clk-next.

Regards,
Mike