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

["Hajda, Andrzej" <andrzej.hajda@intel.com>]

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

> +{
> +	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);
>