[PATCH v4] clk: expand clk_ignore_unused mechanism to keep only a few clks on
From: Uwe Kleine-König
Date: Wed Mar 29 2023 - 16:46:46 EST
Allow to pass an integer n that results in only keeping n unused clocks
enabled.
This helps to debug the problem if you only know that clk_ignore_unused
helps but you have no clue yet which clock is the culprit.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
Hello Stephen,
On Wed, Mar 29, 2023 at 12:49:19PM -0700, Stephen Boyd wrote:
> Quoting Uwe Kleine-König (2022-10-26 08:18:12)
> > Documentation/driver-api/clk.rst | 4 +++-
>
> No update to Documentation/admin-guide/kernel-parameters.txt?
Fair request. I mentioned it there that you can assign an integer but
refer to Documentation/driver-api/clk.rst for the details.
> > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > index c3c3f8c07258..356119a7e5fe 100644
> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > [...]
> > @@ -1352,12 +1354,17 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
> > * back to .disable
> > */
> > if (clk_core_is_enabled(core)) {
> > - trace_clk_disable(core);
> > - if (core->ops->disable_unused)
> > - core->ops->disable_unused(core->hw);
> > - else if (core->ops->disable)
> > - core->ops->disable(core->hw);
> > - trace_clk_disable_complete(core);
> > + if (clk_unused_keep_on) {
> > + pr_warn("Keep unused clk \"%s\" on\n", core->name);
> > + clk_unused_keep_on -= 1;
> > + } else {
> > + trace_clk_disable(core);
>
> We have trace_clk_disable() here. Can you have this tracepoint print to
> the kernel log and watch over serial console? That would be faster than
> bisecting.
Well no, that doesn't work for all the problems where
clk_ignore_unused=7 could be useful. Consider that e.g. you know that
eth0 is broken, but with clk_ignore_unused is works. So one of the (say)
25 nominally unused clks are required for eth0. But it's not possible to
test the network after each of the 25 clk_disable()s. Unless I'm missing
something and you can hook a userspace action on a trace line?!
> > + if (core->ops->disable_unused)
> > + core->ops->disable_unused(core->hw);
> > + else if (core->ops->disable)
> > + core->ops->disable(core->hw);
> > + trace_clk_disable_complete(core);
> > + }
> > }
> >
> > unlock_out:
> > @@ -1369,9 +1376,17 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
> > }
> >
> > static bool clk_ignore_unused __initdata;
> > -static int __init clk_ignore_unused_setup(char *__unused)
> > +static int __init clk_ignore_unused_setup(char *keep)
> > {
> > - clk_ignore_unused = true;
> > + if (*keep == '=') {
> > + int ret;
> > +
> > + ret = kstrtouint(keep + 1, 0, &clk_unused_keep_on);
> > + if (ret < 0)
>
> Could omit 'ret' and just have if (kstrtouint(..))
I don't feel strong, but I think having that on two lines is easier to
read. So I kept it as is, but if you insist, I can change.
> > + pr_err("Warning: failed to parse clk_ignore_unused parameter, ignoring");
>
> Missing newline on printk.
fixed.
Best regards
Uwe
.../admin-guide/kernel-parameters.txt | 6 ++--
Documentation/driver-api/clk.rst | 4 ++-
drivers/clk/clk.c | 33 ++++++++++++++-----
3 files changed, 32 insertions(+), 11 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6221a1d057dd..1a378fe94e48 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -600,8 +600,10 @@
force such clocks to be always-on nor does it reserve
those clocks in any way. This parameter is useful for
debug and development, but should not be needed on a
- platform with proper driver support. For more
- information, see Documentation/driver-api/clk.rst.
+ platform with proper driver support.
+ It can take a value (e.g. clk_ignore_unused=7), to only
+ disable some clks. For more information, see
+ Documentation/driver-api/clk.rst.
clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
[Deprecated]
diff --git a/Documentation/driver-api/clk.rst b/Documentation/driver-api/clk.rst
index 3cad45d14187..65ae7c3e2b33 100644
--- a/Documentation/driver-api/clk.rst
+++ b/Documentation/driver-api/clk.rst
@@ -259,7 +259,9 @@ 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.
+kernel. If you pass "clk_ignore_unused=n" (where n is an integer) the first n
+found clocks are not disabled which can be useful for bisecting over the unused
+clks if you don't know yet which of them is reponsible for your problem.
Locking
=======
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index ae07685c7588..87f605a4f791 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1343,6 +1343,8 @@ static void __init clk_unprepare_unused_subtree(struct clk_core *core)
clk_pm_runtime_put(core);
}
+static unsigned clk_unused_keep_on __initdata;
+
static void __init clk_disable_unused_subtree(struct clk_core *core)
{
struct clk_core *child;
@@ -1373,12 +1375,17 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
* back to .disable
*/
if (clk_core_is_enabled(core)) {
- trace_clk_disable(core);
- if (core->ops->disable_unused)
- core->ops->disable_unused(core->hw);
- else if (core->ops->disable)
- core->ops->disable(core->hw);
- trace_clk_disable_complete(core);
+ if (clk_unused_keep_on) {
+ pr_warn("Keep unused clk \"%s\" on\n", core->name);
+ clk_unused_keep_on -= 1;
+ } else {
+ trace_clk_disable(core);
+ if (core->ops->disable_unused)
+ core->ops->disable_unused(core->hw);
+ else if (core->ops->disable)
+ core->ops->disable(core->hw);
+ trace_clk_disable_complete(core);
+ }
}
unlock_out:
@@ -1390,9 +1397,17 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
}
static bool clk_ignore_unused __initdata;
-static int __init clk_ignore_unused_setup(char *__unused)
+static int __init clk_ignore_unused_setup(char *keep)
{
- clk_ignore_unused = true;
+ if (*keep == '=') {
+ int ret;
+
+ ret = kstrtouint(keep + 1, 0, &clk_unused_keep_on);
+ if (ret < 0)
+ pr_err("Warning: failed to parse clk_ignore_unused parameter, ignoring\n");
+ } else {
+ clk_ignore_unused = true;
+ }
return 1;
}
__setup("clk_ignore_unused", clk_ignore_unused_setup);
@@ -1404,6 +1419,8 @@ static int __init clk_disable_unused(void)
if (clk_ignore_unused) {
pr_warn("clk: Not disabling unused clocks\n");
return 0;
+ } else if (clk_unused_keep_on) {
+ pr_warn("clk: Not disabling %u unused clocks\n", clk_unused_keep_on);
}
clk_prepare_lock();
--
2.39.2
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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