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 | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 517e92c6a70b..e5cf049c18f8 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -965,22 +965,19 @@ 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);
@@ -1959,7 +1956,7 @@ static void execlists_reset(struct intel_engine_cs *engine,
spin_unlock(&engine->timeline.lock);
/* Following the reset, we need to reload the CSB read/write pointers */
- engine->execlists.csb_head = -1;
+ engine->execlists.csb_head = GEN8_CSB_ENTRIES - 1;
local_irq_restore(flags);
@@ -2460,7 +2457,7 @@ static int logical_ring_init(struct intel_engine_cs *engine)
upper_32_bits(ce->lrc_desc);
}
- engine->execlists.csb_head = -1;
+ engine->execlists.csb_head = GEN8_CSB_ENTRIES - 1;
return 0;
--
2.17.1
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