3 files changed, 32 insertions, 0 deletions

diff --git a/Documentation/clk.txt b/Documentation/clk.txt
index 4274a546eb57..b9911c27f496 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 4609e81dbc37..9aa5562fed9c 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.
         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 20ce67f82d65..934cfd18f72d 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)