drm/i915/dmc_wl: Do not check for DMC payload

Enabling and disabling of DMC wakelock is already coupled with enabling
and disabling of dynamic DC states, which already depend on the DMC
being properly loaded. As such, we do not need to check if we already
have a DMC payload parsed in __intel_dmc_wl_supported().

Furthermore, the presence of such a check causes inconsistencies in the
refcount if the following sequence of events happen:

  1. A call to one of the register accessors from intel_de.h is done
     before the DMC payload is parsed. That causes intel_dmc_wl_get() to
     be called. Suppose the register offset qualifies as needing the
     wakelock.

     In normal circumstances, the refcount would be incremented, but,
     because __intel_dmc_wl_supported() returns false, the refcount is
     untouched.

  2. In a separate worker thread, the DMC firmware is parsed. Parsing of
     the DMC payload is finished before the corresponding
     intel_dmc_wl_put() from (1) is called.

  3. When in the context of (1), intel_dmc_wl_put() gets called, now we
     have __intel_dmc_wl_supported() returning true and we hit the
     warning, because the code doesn't expect a zero refcount.

Let's remove that check, since it is unnecessary and causes the
inconsistency illustrated above.

Reviewed-by: Krzysztof Karas <krzysztof.karas@intel.com>
Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250124191250.56833-1-gustavo.sousa@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_dmc_wl.c b/drivers/gpu/drm/i915/display/intel_dmc_wl.c
index 86ba159b683c7f220ecd65c5a7c3202fa92c3617..7e2ce0c2f6c391c063237b28c092254769a09533 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dmc_wl.c
+++ b/drivers/gpu/drm/i915/display/intel_dmc_wl.c
@@ -10,7 +10,6 @@
 #include "i915_drv.h"
 #include "i915_reg.h"
 #include "intel_de.h"
-#include "intel_dmc.h"
 #include "intel_dmc_regs.h"
 #include "intel_dmc_wl.h"
 
@@ -283,7 +282,7 @@ static bool intel_dmc_wl_check_range(struct intel_display *display,
 
 static bool __intel_dmc_wl_supported(struct intel_display *display)
 {
-       return display->params.enable_dmc_wl && intel_dmc_has_payload(display);
+       return display->params.enable_dmc_wl;
 }
 
 static void intel_dmc_wl_sanitize_param(struct intel_display *display)