We can avoid the mmio read of the CSB pointers after reset based on the
knowledge that the HW always start writing at entry 0 in the CSB buffer.
We need to reset our CSB head tracking after GPU reset (and on
sanitization after resume) so that we are expecting to read from entry
0.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_lrc.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 6d3b03299b0c..14149d0912fb 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -981,22 +981,19 @@ static void process_csb(struct intel_engine_cs *engine)
&engine->status_page.page_addr[I915_HWS_CSB_BUF0_INDEX];
unsigned int head, tail;
- if (unlikely(execlists->csb_use_mmio)) {
- buf = (u32 * __force)
- (i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_BUF_LO(engine, 0)));
- execlists->csb_head = -1; /* force mmio read of CSB */
- }
-
/* Clear before reading to catch new interrupts */
clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
smp_mb__after_atomic();
- if (unlikely(execlists->csb_head == -1)) { /* after a reset */
+ if (unlikely(execlists->csb_use_mmio)) {
if (!fw) {
intel_uncore_forcewake_get(i915, execlists->fw_domains);
fw = true;
}
+ buf = (u32 * __force)
+ (i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_BUF_LO(engine, 0)));
+
head = readl(i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)));
tail = GEN8_CSB_WRITE_PTR(head);
head = GEN8_CSB_READ_PTR(head);
@@ -1790,9 +1787,6 @@ static void enable_execlists(struct intel_engine_cs *engine)
I915_WRITE(RING_HWS_PGA(engine->mmio_base),
engine->status_page.ggtt_offset);
POSTING_READ(RING_HWS_PGA(engine->mmio_base));
-
- /* Following the reset, we need to reload the CSB read/write pointers */
- engine->execlists.csb_head = -1;
}
static int gen8_init_common_ring(struct intel_engine_cs *engine)
@@ -1945,6 +1939,9 @@ static void execlists_reset(struct intel_engine_cs *engine,
__unwind_incomplete_requests(engine);
spin_unlock(&engine->timeline.lock);
+ /* Following the reset, we need to reload the CSB read/write pointers */
+ engine->execlists.csb_head = GEN8_CSB_ENTRIES - 1;
+
local_irq_restore(flags);
/*
@@ -2436,6 +2433,8 @@ static int logical_ring_init(struct intel_engine_cs *engine)
upper_32_bits(ce->lrc_desc);
}
+ engine->execlists.csb_head = GEN8_CSB_ENTRIES - 1;
+
return 0;
error:
--
2.17.0
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