Re: [Intel-gfx] [PATCH v3] drm/i915: Do not cover all future platforms in TLB invalidation

[Matt Roper <matthew.d.roper@intel.com>]

On Mon, Jan 09, 2023 at 12:24:42PM +0000, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> Revert to the original explicit approach and document the reasoning
> behind it.
> 
> v2:
>  * DG2 needs to be covered too. (Matt)
> 
> v3:
>  * Full version check for Gen12 to avoid catching all future platforms.
>    (Matt)
> 
> 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> # v1

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>

> ---
>  drivers/gpu/drm/i915/gt/intel_gt.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 7eeee5a7cb33..5521fa057aab 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -1070,10 +1070,23 @@ 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) &&
> +	    GRAPHICS_VER_FULL(i915) <= IP_VER(12, 55)) {
>  		regs = NULL;
>  		num = ARRAY_SIZE(xehp_regs);
> -	} else if (GRAPHICS_VER(i915) == 12) {
> +	} else if (GRAPHICS_VER_FULL(i915) == IP_VER(12, 0) ||
> +		   GRAPHICS_VER_FULL(i915) == IP_VER(12, 10)) {
>  		regs = gen12_regs;
>  		num = ARRAY_SIZE(gen12_regs);
>  	} else if (GRAPHICS_VER(i915) >= 8 && GRAPHICS_VER(i915) <= 11) {
> -- 
> 2.34.1
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation