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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 02 Jul 2025, Gustavo Sousa <gustavo.sousa@intel.com> wrote:
> 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.

The solution would be to make the function:

bool __intel_display_wa(struct intel_display *display, enum intel_display_wa wa, const char *name);

and the macro:

#define intel_display_wa(__display, __wa) \
	__intel_display_wa((__display), INTEL_DISPLAY_WA_##__wa, __stringify(__wa))

and then you could debug log the name.

Worth it? Not sure.


BR,
Jani.


>
> --
> 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
>>

-- 
Jani Nikula, Intel