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

[Nautiyal, Ankit K]

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


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.
>