[PATCH RFC 00/46] mmc: mmc: Add Software Command Queuing

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Hi

Chuanxiao Dong sent some patches last year relating to eMMC 5.1 Software
Command Queuing.  He did not follow-up but I have contacted him and he says
it is OK if I take over upstreaming the patches.

eMMC Command Queuing is a feature added in version 5.1.  The card maintains
a queue of up to 32 data transfers.  Commands CMD45/CMD45 are sent to queue
up transfers in advance, and then one of the transfers is selected to
"execute" by CMD46/CMD47 at which point data transfer actually begins.

The advantage of command queuing is that the card can prepare for transfers
in advance.  That makes a big difference in the case of random reads because
the card can start reading into its cache in advance.

A v5.1 host controller can manage the command queue itself, but it is also
possible for software to manage the queue using an non-v5.1 host controller
- that is what Software Command Queuing is.

Refer to the JEDEC (http://www.jedec.org/) eMMC v5.1 Specification for more
information about Command Queuing.

While these patches are heavily based on Dong's patches, there are some
changes:

SDHCI has been amended to support commands during transfer. That is a
generic change added in patches 1 - 22. In principle, that would also
support SDIO's CMD52 during data transfer.

The original approach added multiple commands into the same request for
sending CMD44, CMD45 and CMD13. That is not strictly necessary and has
been omitted for now.

The original approach also called blk_end_request() from the mrq->done()
function, which means the upper layers learnt of completed requests
slightly earlier. That is not strictly related to Software Command Queuing
and is something that could potentially be done for all data requests.
That has been omitted for now.

The current block driver supports 2 requests on the go at a time. Patches
23 - 30 make preparations for an arbitrary sized queue. Patches 31 - 34
introduce Command Queue definitions and helpers.  Patches 35 - 41
complete the job of making the block driver use a queue.  Patches 42 - 44
finally add Software Command Queuing, and 45 - 46 enable it for Intel eMMC
controllers. Most of the Software Command Queuing functionality is added
in patch 43.

The patches can also be found here:

	http://git.infradead.org/users/ahunter/linux-sdhci.git/shortlog/refs/heads/swcmdq

The patches have only had basic testing so far. Ad-hoc testing shows a
degradation in sequential read performance of about 10% but an increase in
throughput for mixed workload of multiple processes of about 90%. The
reduction in sequential performance is due to the need to read the Queue
Status register between each transfer.

These patches should not conflict with Hardware Command Queuing which
handles the queue in a completely different way and thus does not need
to share code with Software Command Queuing. The exceptions being the
Command Queue definitions and queue allocation which should be able to be
used.


Adrian Hunter (46):
      mmc: core: Add support for sending commands during data transfer
      mmc: mmc_test: Add tests for sending commands during transfer
      mmc: sdhci: Move busy signal handling into sdhci_finish_cmd()
      mmc: sdhci: Get rid of redundant BUG_ONs
      mmc: sdhci: Simplify sdhci_finish_command() by clearing host->cmd at the start
      mmc: sdhci: Record what command is using the data lines
      mmc: sdhci: Get rid of host->busy_handle
      mmc: sdhci: Reduce the use of host->mrq
      mmc: sdhci: Move host->data warning
      mmc: sdhci: Factor out sdhci_finish_mrq()
      mmc: sdhci: Factor out sdhci_needs_reset()
      mmc: sdhci: Track whether a reset is pending
      mmc: sdhci: Clear pointers when a request finishes
      mmc: sdhci: Ensure all requests get errored out
      mmc: sdhci: Factor out sdhci_data_line_cmd()
      mmc: sdhci: Separate timer timeout for command and data requests
      mmc: sdhci: Allow for finishing multiple requests
      mmc: sdhci: Factor out sdhci_auto_cmd12()
      mmc: sdhci: Do not reset cmd or data circuits that are in use
      mmc: sdhci: Support cap_cmd_during_tfr requests
      mmc: sdhci-pci: Set MMC_CAP_CMD_DURING_TFR for Intel eMMC controllers
      mmc: sdhci-acpi: Set MMC_CAP_CMD_DURING_TFR for Intel eMMC controllers
      mmc: queue: Fix queue thread wake-up
      mmc: queue: Factor out mmc_queue_alloc_bounce_bufs()
      mmc: queue: Factor out mmc_queue_alloc_bounce_sgs()
      mmc: queue: Factor out mmc_queue_alloc_sgs()
      mmc: queue: Factor out mmc_queue_reqs_free_bufs()
      mmc: queue: Introduce queue depth
      mmc: queue: Use queue depth to allocate and free
      mmc: queue: Allocate queue of size qdepth
      mmc: mmc: Add Command Queue definitions
      mmc: mmc: Add functions to enable / disable the Command Queue
      mmc: mmc_test: Disable Command Queue while mmc_test is used
      mmc: block: Disable Command Queue while RPMB is used
      mmc: core: Do not prepare a new request twice
      mmc: core: Export mmc_retune_hold() and mmc_retune_release()
      mmc: block: Factor out mmc_blk_requeue()
      mmc: block: Fix 4K native sector check
      mmc: block: Use local var for mqrq_cur
      mmc: block: Pass mqrq to mmc_blk_prep_packed_list()
      mmc: block: Introduce queue semantics
      mmc: queue: Add a function to control wake-up on new requests
      mmc: block: Add Software Command Queuing
      mmc: mmc: Enable Software Command Queuing
      mmc: sdhci-pci: Enable Software Command Queuing for some Intel controllers
      mmc: sdhci-acpi: Enable Software Command Queuing for some Intel controllers

 drivers/mmc/card/block.c          | 738 +++++++++++++++++++++++++++++++++++---
 drivers/mmc/card/mmc_test.c       | 316 ++++++++++++++++
 drivers/mmc/card/queue.c          | 296 +++++++++------
 drivers/mmc/card/queue.h          |  27 +-
 drivers/mmc/core/core.c           | 113 +++++-
 drivers/mmc/core/host.c           |   2 +
 drivers/mmc/core/host.h           |   2 -
 drivers/mmc/core/mmc.c            |  43 ++-
 drivers/mmc/core/mmc_ops.c        |  27 ++
 drivers/mmc/host/sdhci-acpi.c     |   4 +-
 drivers/mmc/host/sdhci-pci-core.c |   1 +
 drivers/mmc/host/sdhci.c          | 391 +++++++++++++-------
 drivers/mmc/host/sdhci.h          |   9 +-
 include/linux/mmc/card.h          |   5 +
 include/linux/mmc/core.h          |  12 +
 include/linux/mmc/host.h          |   9 +-
 include/linux/mmc/mmc.h           |  17 +
 17 files changed, 1686 insertions(+), 326 deletions(-)


Regards
Adrian

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