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

[Lucas De Marchi]

On Thu, Jul 03, 2025 at 03:00:19PM +0530, Nautiyal, Ankit K wrote:
>
>On 7/3/2025 3:19 AM, Ville Syrjälä wrote:
>>On Thu, Jul 03, 2025 at 12:29:37AM +0300, Ville Syrjälä wrote:
>>>On Wed, Jul 02, 2025 at 03:25:21PM -0500, Lucas De Marchi wrote:
>>>>On Wed, Jul 02, 2025 at 10:40:34PM +0300, Ville Syrjälä wrote:
>>>>>On Wed, Jul 02, 2025 at 02:16:18PM +0530, Ankit Nautiyal wrote:
>>>>>>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 at intel.com>
>>>>>>Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at 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);
>>>>>>+		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,
>>>>>How is anyone supposed to keep track of these random numbers
>>>>>and what they mean?
>>>>they mean there's a h/w workaround that requires that and this is the id
>>>>if you need to find more details about it or what platforms/IPs use
>>>>that.
>>>I don't want to go look up all the details in the common case.
>>>I just want to read the code and see that it generally makes
>>>sense without having to trawl through the spec/hsd for an
>>>hour every time.
>>>
>>>>>The only time I want to see these numbers is if I really have to
>>>>>open the spec/hsd for it to double check some details. Othwerwise
>>>>>it just seems like pointless noise that makes it harder to follow
>>>>>the code/figure out what the heck is going on.
>>>>what is the alternative? The current status quo checking by platform
>>>>and/or IP version, dissociated from the WA numbers?
>>>I find it easiest if everything is in one place. I think every
>>>w/a generally should have these:
>>>- which hardware is affected
>>>- what other runtime conditions are required to hit the issue
>>>- what is being done to avoid the issue
>>>- a short human readable explanation of the issue
>>>- the w/a number for looking up futher details
>>>
>>>Splitting it all up into random bits and pieces just means more
>>>jumping around all the time, which I find annoying at best.
>>I suppose one could argue for a more formal thing for these three:
>>- which hardware is affected
>>- a short human readable explanation of the issue
>>- the w/a number for looking up futher details
>
>Whether adding comments with platform and relevant information about 
>Wa would be sufficient?
>
>Something like:
>
>/*
> * Wa_16025573575: PTL/WCL

See the nightmare the intel_workarounds.c became. The comments also
don't match what the code is doing which means it's not only noise, it's
wrong information over time.

> * Fix issue with bitbashing on PTL.
> * Set masks bits in GPIO CTL and preserve it during bitbashing sequence.

This description not always can be there. So out of the 3 pieces of
information we already have 2.

> */
>static bool intel_display_needs_wa_16025573575(struct intel_display 
>*display)
>{
>        return DISPLAY_VER(display) == 30;
>}
>
>Or we want to have some wa_struct with fields for platforms and stuff?

on the xe side we check it once during init and set a bitmap to be used
later. This also allows us to check "what W/A is enabled" from outside
and double check the list of the workarounds for a platform.

Lucas De Marchi

>
>
>Regards,
>
>Ankit
>
>>
>>Might be still a real pain to deal with that due to having to jump
>>around, but at least it could be used to force people to document
>>each w/a a bit better.
>>
>>Basically anything that avoids having to wait for the spec/hsd to
>>load is a good thing in my book.
>>
>>There's also the question of what to do with duplicates, as in often
>>it seems the same issue is present on multiple platforms under different
>>w/a numbers.
>>