On Fri, 17 Jan 2025, Gustavo Sousa <gustavo.sousa@xxxxxxxxx> wrote:
> 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.
If the debug struct were an opaque pointer, you could check for that
being != NULL. Register the debugfs always, and have that initialize
everything as needed?
BR,
Jani.
>
> Signed-off-by: Gustavo Sousa <gustavo.sousa@xxxxxxxxx>
> ---
> .../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)
--
Jani Nikula, Intel
