Mesa (master): broadcom: document known hardware issues for L2T flush command
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Fri Oct 18 12:31:55 UTC 2019
Module: Mesa
Branch: master
Commit: 2d8b51ea4d66c817a213e083b09549eb6ae8ba26
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=2d8b51ea4d66c817a213e083b09549eb6ae8ba26
Author: Iago Toral Quiroga <itoral at igalia.com>
Date: Thu Sep 5 08:35:01 2019 +0200
broadcom: document known hardware issues for L2T flush command
Suggested-by: Eric Anholt <eric at anholt.net>
Reviewed-by: Eric Anholt <eric at anholt.net>
---
src/broadcom/cle/v3d_packet_v33.xml | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/src/broadcom/cle/v3d_packet_v33.xml b/src/broadcom/cle/v3d_packet_v33.xml
index f40796612f9..10ed844e23b 100644
--- a/src/broadcom/cle/v3d_packet_v33.xml
+++ b/src/broadcom/cle/v3d_packet_v33.xml
@@ -174,6 +174,41 @@
<value name="int" value="3" min_ver="42"/> <!-- clamp to integer RT's range -->
</enum>
+ <!---
+ CL cache flush commands are not fully documented and subject to a
+ number of hardware issues that make them unreliable. Specifically:
+
+ * The L2T flush command has a 'deferred' bit to ensure the command
+ doesn't execute until all other commands in the CL have completed,
+ which is required to achieve the expected behavior. This bit comes
+ right after the mode field.
+
+ * GFXH-1895: Overlapping write combiner flush requests from different
+ sources are not safe. If two flush requests from different sources
+ overlap, the TMU may send the done signal for the first flush back to
+ the wrong source.
+
+ * GFXH-1888: It is possible for a regular access to sneak past a
+ pending L2T flush. If an L2T flush is requested via L2TCACTL while a
+ CLE-requested flush is in progress, it is possible for a regular
+ access to sneak through in the gap between the CLE flush and the
+ L2TCACTL flush.
+
+ * GFXH-1897: Writing 0 to L2TCACTL clobbers in-progress flush status.
+ Writing 0 to TMUWCF (bit 8) clears the TMUWCF bit, even if a write
+ combiner flush is still in progress. Similarly, writing 0 to L2TFLS
+ (bit 0) clears the L2TFLS bit, even if an L2T flush is still in
+ progress. Writing 0 to L2TFLM (bits 1..2) overwrites the flush mode,
+ even if a flush is not being requested (ie 0 is being written to
+ L2TFLS). If the last flush has not yet made it through the L2T
+ arbiter, this will change the mode of that flush.
+
+ GFXH-1888 and GFXH-1897 are problematic when we don't wait for L2T
+ flushes requested via LATCACTL to complete immediately.
+
+ Because of this, the driver will do all of its flushing via the kernel
+ using L2TCACTL instead of using the CL commands.
+ -->
<enum name="L2T Flush Mode" prefix="L2T_FLUSH_MODE">
<!-- invalidates all cache lines -->
<value name="flush" value="0"/>
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