Re: [PATCH i-g-t 1/2] lib/intel_pat: add intel_pat_has_wt()

["Sundaresan, Sujaritha" <sujaritha.sundaresan@intel.com>]

On 9/8/2026 11:39 AM, Hajda, Andrzej wrote:
> W dniu 4.09.2026 o 10:56, Sujaritha Sundaresan pisze:
>> Not every platform has a write-through entry in its PAT table. Where
>> there is none the KMD reports the UC index for XE_CACHE_WT, so a test
>> which asks for write-through quietly gets uncached instead. Spotting
>> that currently means enumerating IP versions in the test, which needs
>> touching again for every platform added.
>>
>> Add intel_pat_has_wt(), which answers the same question from the PAT
>> config itself: a WT index which aliases UC means there is no distinct
>> write-through entry to test. No functional change; the first user is
>> the next patch.
>>
>> Signed-off-by: Sujaritha Sundaresan <sujaritha.sundaresan@intel.com>
>> ---
>>   lib/intel_pat.c | 22 ++++++++++++++++++++++
>>   lib/intel_pat.h |  2 ++
>>   2 files changed, 24 insertions(+)
>>
>> diff --git a/lib/intel_pat.c b/lib/intel_pat.c
>> index 2f35bb772..782201029 100644
>> --- a/lib/intel_pat.c
>> +++ b/lib/intel_pat.c
>> @@ -284,6 +284,28 @@ uint8_t intel_get_pat_idx_uc_comp(int fd)
>>       return pat.uc_comp;
>>   }
>>   +/**
>> + * intel_pat_has_wt - Check whether the platform has a write-through 
>> PAT index
>> + *
>> + * @fd: DRM device fd
>> + *
>> + * Platforms with no write-through entry in their PAT table report 
>> the UC
>> + * index for XE_CACHE_WT, so a WT index which aliases UC means there 
>> is no
>> + * write-through mode to exercise. Deriving this from the PAT config 
>> rather
>> + * than from a list of IP versions keeps it working for platforms added
>> + * later.
>> + *
>> + * Returns: true if the platform has a distinct write-through pat_index
>> + */
>> +bool intel_pat_has_wt(int fd)
>
> For getters convention is intel_get_pat_idx_*
> So maybe intel_has_pat_wt ?
> Up to you.
>
>
> Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
>
> Regards
> Andrzej

Thanks for the r-b. I will switch it to intel_has_pat_wt.

Regards,

Suja

>
>> +{
>> +    struct intel_pat_cache pat = {};
>> +
>> +    intel_get_pat_idx(fd, &pat);
>> +
>> +    return pat.wt != pat.uc;
>> +}
>> +
>>   uint8_t intel_get_pat_idx_wt(int fd)
>>   {
>>       struct intel_pat_cache pat = {};
>> diff --git a/lib/intel_pat.h b/lib/intel_pat.h
>> index a31b60e86..824f8931e 100644
>> --- a/lib/intel_pat.h
>> +++ b/lib/intel_pat.h
>> @@ -37,6 +37,8 @@ uint8_t intel_get_pat_idx_wb(int fd);
>>     uint8_t intel_get_pat_idx_uc_comp(int fd);
>>   +bool intel_pat_has_wt(int fd);
>> +
>>   int32_t xe_get_pat_sw_config(int drm_fd, struct intel_pat_cache 
>> *xe_pat_cache, int gt);
>>   int32_t xe_get_pat_hw_config(int drm_fd, struct intel_pat_cache 
>> *xe_pat_cache, int gt);
>