[Intel-xe] [PATCH v2] drm/xe/irq: Clear GFX_MSTR_IRQ as part of IRQ reset

[Gustavo Sousa]

Starting with Xe_LP+, GFX_MSTR_IRQ contains status bits that have W1C
behavior. If we do not properly reset them, we would miss delivery of
interrupts if a pending bit is set when enabling IRQs.

As an example, the display part of our probe routine contains paths
where we wait for vblank interrupts. If a display interrupt was already
pending when enabling IRQs, we would time out waiting for the vblank.

That in fact happened recently when modprobing Xe on a Lunar Lake with a
specific configuration; and that's how we found out we were missing this
step in the IRQ enabling logic.

Fix the issue by clearing GFX_MSTR_IRQ as part of the IRQ reset.

v2:
  - Make resetting GFX_MSTR_IRQ be the last step to avoid bit
    re-latching. (Ville)

BSpec: 50875, 54028, 62357
Cc: Lucas De Marchi <lucas.demarchi at intel.com>
Cc: Matt Roper <matthew.d.roper at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa at intel.com>
---
 drivers/gpu/drm/xe/xe_irq.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_irq.c b/drivers/gpu/drm/xe/xe_irq.c
index ccb934f8fa34..cb03f40df272 100644
--- a/drivers/gpu/drm/xe/xe_irq.c
+++ b/drivers/gpu/drm/xe/xe_irq.c
@@ -519,6 +519,13 @@ static void dg1_irq_reset(struct xe_tile *tile)
 	mask_and_disable(tile, PCU_IRQ_OFFSET);
 }
 
+static void dg1_irq_reset_mstr(struct xe_tile *tile)
+{
+	struct xe_gt *mmio = tile->primary_gt;
+
+	xe_mmio_write32(mmio, GFX_MSTR_IRQ, ~0);
+}
+
 static void xe_irq_reset(struct xe_device *xe)
 {
 	struct xe_tile *tile;
@@ -534,6 +541,15 @@ static void xe_irq_reset(struct xe_device *xe)
 	tile = xe_device_get_root_tile(xe);
 	mask_and_disable(tile, GU_MISC_IRQ_OFFSET);
 	xe_display_irq_reset(xe);
+
+	/*
+	 * The tile's top-level status register should be the last one
+	 * to be reset to avoid possible bit re-latching from lower
+	 * level interrupts.
+	 */
+	for_each_tile(tile, xe, id)
+		if (GRAPHICS_VERx100(xe) >= 1210)
+			dg1_irq_reset_mstr(tile);
 }
 
 static void xe_irq_postinstall(struct xe_device *xe)
-- 
2.42.0