Re: [PATCH 1/2] drm/i915/display_wa: Add helpers to check wa

[Gustavo Sousa <gustavo.sousa@intel.com>]

Quoting Ankit Nautiyal (2025-07-02 05:46:18-03:00)
>Introduce a generic helper to check display workarounds using an enum.
>
>Convert Wa_16023588340 to use the new interface, simplifying WA checks
>and making future additions easier.
>
>v2: Use drm_WARN instead of MISSING_CASE and simplify intel_display_wa
>macro. (Jani)
>
>Suggested-by: Jani Nikula <jani.nikula@intel.com>
>Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>---
> drivers/gpu/drm/i915/display/intel_display_wa.c | 15 +++++++++++++++
> drivers/gpu/drm/i915/display/intel_display_wa.h |  9 +++++++++
> drivers/gpu/drm/i915/display/intel_fbc.c        |  2 +-
> 3 files changed, 25 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.c b/drivers/gpu/drm/i915/display/intel_display_wa.c
>index f57280e9d041..f5e8d58d9a68 100644
>--- a/drivers/gpu/drm/i915/display/intel_display_wa.c
>+++ b/drivers/gpu/drm/i915/display/intel_display_wa.c
>@@ -3,6 +3,8 @@
>  * Copyright © 2023 Intel Corporation
>  */
> 
>+#include "drm/drm_print.h"
>+
> #include "i915_reg.h"
> #include "intel_de.h"
> #include "intel_display_core.h"
>@@ -39,3 +41,16 @@ void intel_display_wa_apply(struct intel_display *display)
>         else if (DISPLAY_VER(display) == 11)
>                 gen11_display_wa_apply(display);
> }
>+
>+bool __intel_display_wa(struct intel_display *display, enum intel_display_wa wa)
>+{
>+        switch (wa) {
>+        case INTEL_DISPLAY_WA_16023588340:
>+                return intel_display_needs_wa_16023588340(display);
>+        default:
>+                drm_WARN(display->drm, 1, "Missing Wa number: %d\n", wa);

Hm... I wonder how useful the message would be if we just show the enum
value. For example, if the next workaround that we added was
INTEL_DISPLAY_WA_99999999999 and we had it missing here, I think we
would get the following warning message:

    "Missing Wa number: 1"

Perhaps the enum identifier could be found in the callstack that is
presented with the warning, but I'm wondering if we could do better
here.

Not sure there is a good solution without requiring extra memory to map
each enum member to its corresponding the workaround number.

--
Gustavo Sousa

>+                break;
>+        }
>+
>+        return false;
>+}
>diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.h b/drivers/gpu/drm/i915/display/intel_display_wa.h
>index babd9d16603d..146ee70d66f7 100644
>--- a/drivers/gpu/drm/i915/display/intel_display_wa.h
>+++ b/drivers/gpu/drm/i915/display/intel_display_wa.h
>@@ -21,4 +21,13 @@ static inline bool intel_display_needs_wa_16023588340(struct intel_display *disp
> bool intel_display_needs_wa_16023588340(struct intel_display *display);
> #endif
> 
>+enum intel_display_wa {
>+        INTEL_DISPLAY_WA_16023588340,
>+};
>+
>+bool __intel_display_wa(struct intel_display *display, enum intel_display_wa wa);
>+
>+#define intel_display_wa(__display, __wa) \
>+        __intel_display_wa((__display), INTEL_DISPLAY_WA_##__wa)
>+
> #endif
>diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
>index 6e26cb4c5724..e2e03af520b2 100644
>--- a/drivers/gpu/drm/i915/display/intel_fbc.c
>+++ b/drivers/gpu/drm/i915/display/intel_fbc.c
>@@ -1464,7 +1464,7 @@ static int intel_fbc_check_plane(struct intel_atomic_state *state,
>                 return 0;
>         }
> 
>-        if (intel_display_needs_wa_16023588340(display)) {
>+        if (intel_display_wa(display, 16023588340)) {
>                 plane_state->no_fbc_reason = "Wa_16023588340";
>                 return 0;
>         }
>-- 
>2.45.2
>