drm/i915: Do not cover all future platforms in TLB invalidation

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)

v4:
 * Be totally explicit on the Gen12 branch. (Andrzej)

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>
Link: https://patchwork.freedesktop.org/patch/msgid/20230110113533.744436-1-tvrtko.ursulin@linux.intel.com

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 7eeee5a..5721bf8 100644 (file)
--- 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) {