Re: [Intel-gfx] [PATCH 1/2] drm/i915: Do not cover all future platforms in TLB invalidation

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

On 19.12.2022 11:13, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> Revert to the original explicit approach and document the reasoning
> behind it.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
> Cc: Andrzej Hajda <andrzej.hajda@intel.com>

Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>

Regards
Andrzej

> ---
>   drivers/gpu/drm/i915/gt/intel_gt.c | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 7eeee5a7cb33..854841a731cb 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -1070,7 +1070,18 @@ static void mmio_invalidate_full(struct intel_gt *gt)
>   	unsigned int num = 0;
>   	unsigned long flags;
>   
> -	if (GRAPHICS_VER_FULL(i915) >= IP_VER(12, 50)) {
> +	/*
> +	 * New platforms should not be added with catch-all-newer (>=)
> +	 * condition so that any later platform added triggers the below warning
> +	 * and in turn mandates a human cross-check of whether the invalidation
> +	 * flows have compatible semantics.
> +	 *
> +	 * For instance with the 11.00 -> 12.00 transition three out of five
> +	 * respective engine registers were moved to masked type. Then after the
> +	 * 12.00 -> 12.50 transition multi cast handling is required too.
> +	 */
> +
> +	if (GRAPHICS_VER_FULL(i915) == IP_VER(12, 50)) {
>   		regs = NULL;
>   		num = ARRAY_SIZE(xehp_regs);
>   	} else if (GRAPHICS_VER(i915) == 12) {