I think this patch is a worthwhile cleanup even if it might look only marginally
useful. It gets more useful in upcoming patches and for handling of future GEN
platforms.
The only non-mechanical part of this is the removal of the extra & operation on
the ring->next_context_status_buffer. This is safe because right above this, we
already did a modulus operation.
Signed-off-by: Ben Widawsky <benjamin.widawsky@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_debugfs.c | 6 +++---
drivers/gpu/drm/i915/intel_lrc.c | 15 +++++++++------
drivers/gpu/drm/i915/intel_lrc.h | 18 ++++++++++++++++--
3 files changed, 28 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 0fc38bb..3b05bd1 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2092,13 +2092,13 @@ static int i915_execlists(struct seq_file *m, void *data)
seq_printf(m, "\tStatus pointer: 0x%08X\n", status_pointer);
read_pointer = ring->next_context_status_buffer;
- write_pointer = status_pointer & 0x07;
+ write_pointer = GEN8_CSB_WRITE_PTR(status_pointer);
if (read_pointer > write_pointer)
- write_pointer += 6;
+ write_pointer += GEN8_CSB_ENTRIES;
seq_printf(m, "\tRead pointer: 0x%08X, write pointer 0x%08X\n",
read_pointer, write_pointer);
- for (i = 0; i < 6; i++) {
+ for (i = 0; i < GEN8_CSB_ENTRIES; i++) {
status = I915_READ(RING_CONTEXT_STATUS_BUF_LO(ring, i));
ctx_id = I915_READ(RING_CONTEXT_STATUS_BUF_HI(ring, i));
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 8096c6a..7fb2035 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -516,7 +516,7 @@ void intel_lrc_irq_handler(struct intel_engine_cs *ring)
status_pointer = I915_READ(RING_CONTEXT_STATUS_PTR(ring));
read_pointer = ring->next_context_status_buffer;
- write_pointer = status_pointer & GEN8_CSB_PTR_MASK;
+ write_pointer = GEN8_CSB_WRITE_PTR(status_pointer);
if (read_pointer > write_pointer)
write_pointer += GEN8_CSB_ENTRIES;
@@ -559,10 +559,11 @@ void intel_lrc_irq_handler(struct intel_engine_cs *ring)
WARN(submit_contexts > 2, "More than two context complete events?\n");
ring->next_context_status_buffer = write_pointer % GEN8_CSB_ENTRIES;
+ /* Update the read pointer to the old write pointer. Manual ringbuffer
+ * management ftw </sarcasm> */
I915_WRITE(RING_CONTEXT_STATUS_PTR(ring),
- _MASKED_FIELD(GEN8_CSB_PTR_MASK << 8,
- ((u32)ring->next_context_status_buffer &
- GEN8_CSB_PTR_MASK) << 8));
+ _MASKED_FIELD(GEN8_CSB_READ_PTR_MASK,
+ ring->next_context_status_buffer << 8));
}
static int execlists_context_queue(struct drm_i915_gem_request *request)
@@ -1506,9 +1507,11 @@ static int gen8_init_common_ring(struct intel_engine_cs *ring)
* | Suspend-to-idle (freeze) | Suspend-to-RAM (mem) |
* BDW | CSB regs not reset | CSB regs reset |
* CHT | CSB regs not reset | CSB regs not reset |
+ * SKL | ? | ? |
+ * BXT | ? | ? |
*/
- next_context_status_buffer_hw = (I915_READ(RING_CONTEXT_STATUS_PTR(ring))
- & GEN8_CSB_PTR_MASK);
+ next_context_status_buffer_hw =
+ GEN8_CSB_WRITE_PTR(I915_READ(RING_CONTEXT_STATUS_PTR(ring)));
/*
* When the CSB registers are reset (also after power-up / gpu reset),
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index ae90f86..de41ad6 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -25,8 +25,6 @@
#define _INTEL_LRC_H_
#define GEN8_LR_CONTEXT_ALIGN 4096
-#define GEN8_CSB_ENTRIES 6
-#define GEN8_CSB_PTR_MASK 0x07
/* Execlists regs */
#define RING_ELSP(ring) _MMIO((ring)->mmio_base + 0x230)
@@ -40,6 +38,22 @@
#define RING_CONTEXT_STATUS_BUF_HI(ring, i) _MMIO((ring)->mmio_base + 0x370 + (i) * 8 + 4)
#define RING_CONTEXT_STATUS_PTR(ring) _MMIO((ring)->mmio_base + 0x3a0)
+/* The docs specify that the write pointer wraps around after 5h, "After status
+ * is written out to the last available status QW at offset 5h, this pointer
+ * wraps to 0."
+ *
+ * Therefore, one must infer than even though there are 3 bits available, 6 and
+ * 7 appear to be * reserved.
+ */
+#define GEN8_CSB_ENTRIES 6
+#define GEN8_CSB_PTR_MASK 0x7
+#define GEN8_CSB_READ_PTR_MASK (GEN8_CSB_PTR_MASK << 8)
+#define GEN8_CSB_WRITE_PTR_MASK (GEN8_CSB_PTR_MASK << 0)
+#define GEN8_CSB_WRITE_PTR(csb_status) \
+ (((csb_status) & GEN8_CSB_WRITE_PTR_MASK) >> 0)
+#define GEN8_CSB_READ_PTR(csb_status) \
+ (((csb_status) & GEN8_CSB_READ_PTR_MASK) >> 8)
+
/* Logical Rings */
int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request);
int intel_logical_ring_reserve_space(struct drm_i915_gem_request *request);
--
2.6.4
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