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

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On 09.01.2023 13:24, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

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@xxxxxxxxx>
Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan@xxxxxxxxx>
Cc: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx> # v1
---
  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)) {

MTL support is lost? IP_VER(12, 70)

And again it looks for me inconsistent, some unknown platforms are covered, for example 12.54, some not, for example 12.11.

Regards
Andrzej

  		regs = gen12_regs;
  		num = ARRAY_SIZE(gen12_regs);
  	} else if (GRAPHICS_VER(i915) >= 8 && GRAPHICS_VER(i915) <= 11) {




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