[PATCH 4/4] drm/i915/dmc_wl: Enable the debugfs only with enable_dmc_wl_debugfs=1

[Gustavo Sousa]

We use a spinlock to protect DMC wakelock debugfs data, since it is also
accessed by the core DMC wakelock logic. Taking the spinlock when the
debugfs is not in use introduces a small but unnecessary penalty.

Since the debugfs functionality is only expected to be used for, uh,
debugging sessions, let's protect it behind a module parameter
enable_dmc_wl_debugfs. That way, we only take the lock if the feature
was enabled in the first place.

Signed-off-by: Gustavo Sousa <gustavo.so...@intel.com>
---
 .../gpu/drm/i915/display/intel_display_params.c  |  5 +++++
 .../gpu/drm/i915/display/intel_display_params.h  |  1 +
 .../gpu/drm/i915/display/intel_dmc_wl_debugfs.c  | 16 +++++++++++++++-
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_params.c 
b/drivers/gpu/drm/i915/display/intel_display_params.c
index c4f1ab43fc0c..bc36d1b0ef87 100644
--- a/drivers/gpu/drm/i915/display/intel_display_params.c
+++ b/drivers/gpu/drm/i915/display/intel_display_params.c
@@ -133,6 +133,11 @@ intel_display_param_named_unsafe(enable_dmc_wl, int, 0400,
        "(-1=use per-chip default, 0=disabled, 1=enabled, 2=match any register, 
3=always locked) "
        "Default: -1");
 
+intel_display_param_named_unsafe(enable_dmc_wl_debugfs, bool, 0400,
+       "Enable DMC wakelock debugfs"
+       "(0=disabled, 1=enabled) "
+       "Default: 0");
+
 __maybe_unused
 static void _param_print_bool(struct drm_printer *p, const char *driver_name,
                              const char *name, bool val)
diff --git a/drivers/gpu/drm/i915/display/intel_display_params.h 
b/drivers/gpu/drm/i915/display/intel_display_params.h
index 5317138e6044..cb7dc1bc6846 100644
--- a/drivers/gpu/drm/i915/display/intel_display_params.h
+++ b/drivers/gpu/drm/i915/display/intel_display_params.h
@@ -48,6 +48,7 @@ struct drm_printer;
        param(bool, psr_safest_params, false, 0400) \
        param(bool, enable_psr2_sel_fetch, true, 0400) \
        param(int, enable_dmc_wl, -1, 0400) \
+       param(bool, enable_dmc_wl_debugfs, false, 0400) \
 
 #define MEMBER(T, member, ...) T member;
 struct intel_display_params {
diff --git a/drivers/gpu/drm/i915/display/intel_dmc_wl_debugfs.c 
b/drivers/gpu/drm/i915/display/intel_dmc_wl_debugfs.c
index 1493d296ac98..f4e4c7a5a730 100644
--- a/drivers/gpu/drm/i915/display/intel_dmc_wl_debugfs.c
+++ b/drivers/gpu/drm/i915/display/intel_dmc_wl_debugfs.c
@@ -37,6 +37,9 @@
  * which exports a buffer of untracked register offsets and also allows extra
  * register offsets to be tracked by the driver.
  *
+ * The debugfs directory is only exported if the module parameter
+ * enable_dmc_wl_debugfs=1 is passed.
+ *
  * Untracked offsets
  * -----------------
  *
@@ -411,6 +414,9 @@ void intel_dmc_wl_debugfs_register(struct intel_display 
*display)
 {
        struct dentry *dir;
 
+       if (!display->params.enable_dmc_wl_debugfs)
+               return;
+
        if (!HAS_DMC_WAKELOCK(display))
                return;
 
@@ -453,6 +459,9 @@ void intel_dmc_wl_debugfs_log_untracked(struct 
intel_display *display, u32 offse
        struct intel_dmc_wl_dbg *dbg = &display->wl.dbg;
        unsigned long flags;
 
+       if (!display->params.enable_dmc_wl_debugfs)
+               return;
+
        spin_lock_irqsave(&dbg->lock, flags);
 
        if (!dbg->untracked.size)
@@ -479,9 +488,14 @@ void intel_dmc_wl_debugfs_log_untracked(struct 
intel_display *display, u32 offse
 bool intel_dmc_wl_debugfs_offset_in_extra_ranges(struct intel_display 
*display, u32 offset)
 {
        struct intel_dmc_wl_dbg *dbg = &display->wl.dbg;
-       bool ret = false;
+       bool ret;
        unsigned long flags;
 
+       if (!display->params.enable_dmc_wl_debugfs)
+               return false;
+
+       ret = false;
+
        spin_lock_irqsave(&dbg->lock, flags);
 
        if (!dbg->extra_ranges)
-- 
2.48.0