mmc: block: Add write packing control
The write packing control will ensure that read requests latency is
not increased due to long write packed commands.
The trigger for enabling the write packing is managing to pack several
write requests. The number of potential packed requests that will trigger
the packing can be configured via sysfs by writing the required value to:
/sys/block/<block_dev_name>/num_wr_reqs_to_start_packing.
The trigger for disabling the write packing is fetching a read request.
Change-Id: I22e8ab04cd9aca220678784c39306068a0996790
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
diff --git a/Documentation/mmc/mmc-dev-attrs.txt b/Documentation/mmc/mmc-dev-attrs.txt
index 22ae844..08f7312 100644
--- a/Documentation/mmc/mmc-dev-attrs.txt
+++ b/Documentation/mmc/mmc-dev-attrs.txt
@@ -8,6 +8,23 @@
force_ro Enforce read-only access even if write protect switch is off.
+ num_wr_reqs_to_start_packing This attribute is used to determine
+ the trigger for activating the write packing, in case the write
+ packing control feature is enabled.
+
+ When the MMC manages to reach a point where num_wr_reqs_to_start_packing
+ write requests could be packed, it enables the write packing feature.
+ This allows us to start the write packing only when it is beneficial
+ and has minimum affect on the read latency.
+
+ The number of potential packed requests that will trigger the packing
+ can be configured via sysfs by writing the required value to:
+ /sys/block/<block_dev_name>/num_wr_reqs_to_start_packing.
+
+ The default value of num_wr_reqs_to_start_packing was determined by
+ running parallel lmdd write and lmdd read operations and calculating
+ the max number of packed writes requests.
+
SD and MMC Device Attributes
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