mmc: block: Add CQE support
authorAdrian Hunter <adrian.hunter@intel.com>
Wed, 29 Nov 2017 13:41:04 +0000 (15:41 +0200)
committerUlf Hansson <ulf.hansson@linaro.org>
Mon, 11 Dec 2017 11:44:34 +0000 (12:44 +0100)
commit1e8e55b67030c6a2fef893d428bdcd611f73705c
tree3b6b1d8a5dc6a336ffb1058c02bdb4e50fe90c84
parent81196976ed946cbf36bb41ddda402853c7df7cfa
mmc: block: Add CQE support

Add CQE support to the block driver, including:
    - optionally using DCMD for flush requests
    - "manually" issuing discard requests
    - issuing read / write requests to the CQE
    - supporting block-layer timeouts
    - handling recovery
    - supporting re-tuning

CQE offers 25% - 50% better random multi-threaded I/O.  There is a slight
(e.g. 2%) drop in sequential read speed but no observable change to sequential
write.

CQE automatically sends the commands to complete requests.  However it only
supports reads / writes and so-called "direct commands" (DCMD).  Furthermore
DCMD is limited to one command at a time, but discards require 3 commands.
That makes issuing discards through CQE very awkward, but some CQE's don't
support DCMD anyway.  So for discards, the existing non-CQE approach is
taken, where the mmc core code issues the 3 commands one at a time i.e.
mmc_erase(). Where DCMD is used, is for issuing flushes.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
drivers/mmc/core/block.c
drivers/mmc/core/block.h
drivers/mmc/core/queue.c
drivers/mmc/core/queue.h