[PATCH v2] drm/i915: Do not cover all future platforms in TLB invalidation

[Matt Roper]

On Fri, Jan 06, 2023 at 10:38:35AM +0000, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Revert to the original explicit approach and document the reasoning
> behind it.
> 
> v2:
>  * DG2 needs to be covered too. (Matt)
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan at intel.com>
> Cc: Andrzej Hajda <andrzej.hajda at intel.com>
> Reviewed-by: Andrzej Hajda <andrzej.hajda at intel.com> # v1
> ---
> Matt, does DG1 need to be in the MCR branch or plain Gen12?

DG1 should use the same "gen12" branch as TGL/RKL/ADL.  Bspec page 66696
is the relevant MMIO table for DG1 and the range containing the TLB
invalidation registers is not a multicast/replicated range.  The types
of engines supported, and the register details for each engine are also
the same as TGL/RKL/ADL.

> ---
>  drivers/gpu/drm/i915/gt/intel_gt.c | 14 +++++++++++++-
>  1 file changed, 13 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..b2556a3d8a3f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -1070,7 +1070,19 @@ 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) {

Did you want to switch this one to

        GRAPHICS_VER_FULL(i915) == IP_VER(12, 0) ||
        GRAPHICS_VER_FULL(i915) == IP_VER(12, 10)

so that it won't automatically pick up future 12.xx platforms like PVC,
MTL, and whatever else might show up in that category in the future?


Matt

> -- 
> 2.34.1
> 

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