clk: add clk_ignore_unused option to keep boot clocks on

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 <olof@lixom.net>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
[mturquette@linaro.org: fixed up trivial merge issue]

diff --git a/Documentation/clk.txt b/Documentation/clk.txt
index 4274a546eb578a0171a2b033c514f21ea3fc53db..b9911c27f496e1aeb5f2cb8f1b3c85345a606459 100644 (file)
--- 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 4609e81dbc37fc2dbfa005ff607890df3a8bbc6b..9aa5562fed9cf03e868348f3ace7e1d01e1730ed 100644 (file)
--- 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.
        DRM     Direct Rendering Management support is enabled.
        DYNAMIC_DEBUG Build in debug messages and enable them at runtime
        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
@@ -465,6 +466,13 @@ 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 20ce67f82d65ddf5acc5dd2b08f294497dbf197c..934cfd18f72ded4a295192f608cc653214c03908 100644 (file)
--- 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)