[RFC PATCH 0/4] Command Queueing Support in eMMC

[Asutosh Das <asutoshd@codeaurora.org>]

In this patch series, we propose a method to add support for
Command Queueing(CQ) feature added to eMMC-5.1 specification.
This feature includes new commands for issuing tasks to the
device and orders the execution of tasks to the device. It
also has task management functions.

The initialization of CQ is decided based on the underlying
driver capability and the capability advertised by the card
through ext_csd. 

We have selectively adopted the scsi design of pulling in
requests from kernel block layer.

In order to support queueing of multiple requests, we have
added a new issue function to mmc-queue. This selectively
pulls the requests and prepares and issues it to the underlying
driver. We have used the inherent tagging mechanism of kernel
block layer to keep track and map tags to the slots of underlying
driver. The current design doesn't block for the request to
complete. We have separated the issuing and completion path
of the request and tracking is done using the tag assigned to
the request.

We have introduced a number of APIs to mmc block layer to
facilitate servicing of requests.

The completion of requests is handled in a softirq registered
with the kernel block layer during initialization. The error
handling however would be done using a workqueue and is under
development.

We have separated the legacy eMMC code from CQ code, so as to
make it more manageable.

A new layer has been introduced to serve the CQ compliant drivers.
This layer (cq_hci) has all the standard functionality implemented.
It also has necessary hooks for convenience of platform drivers.

Asutosh Das (4):
  mmc: queue: initialization of command-queue support
  mmc: card: Add eMMC command queuing support in mmc block layer
  mmc: cmdq: support for command queue enabled host
  mmc: sdhci: add command queue support to sdhci

Sujit Reddy Thumma (1):
  mmc: core: Add support to read command queue parameters

 drivers/mmc/card/block.c   | 378 ++++++++++++++++++++++++++++++++++++++++++++-
 drivers/mmc/card/queue.c   | 160 ++++++++++++++++++-
 drivers/mmc/card/queue.h   |   9 +-
 drivers/mmc/core/core.c    |  87 +++++++++++
 drivers/mmc/core/mmc.c     |  19 +++
 drivers/mmc/core/mmc_ops.c |  45 ++++--
 drivers/mmc/host/Kconfig   |  12 ++
 drivers/mmc/host/Makefile  |   1 +
 drivers/mmc/host/sdhci.c   |  89 +++++++++++
 drivers/mmc/host/sdhci.h   |   2 +
 include/linux/mmc/card.h   |  10 +-
 include/linux/mmc/core.h   |  14 ++
 include/linux/mmc/host.h   |  72 +++++++++
 include/linux/mmc/mmc.h    |   9 ++
 include/linux/mmc/sdhci.h  |   1 +
 15 files changed, 887 insertions(+), 21 deletions(-)

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1.8.2.1

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