[RFC,0/2] Support temporarily disable of the CMDQ mode

Message

Luca Porzio Feb. 15, 2021, 12:31 a.m. UTC

eMMC protocol was born as single threaded and many use cases still
expect single thread operation mode. Through time the Command Queue
was developed and supported but many legacy operation are still
performed using single thread mode.

An example is FFU operation performed by using mmc-utils which is
currently broken for devices supporting CMDQ mode.

In order to enable legacy command sequences, we make cmdq_en sysfs
parameter writeable: setting this parameter to zero will temporarily
disable CMDQ mode and let legacy command sequence be supported.

Setting the cmdq_en parameter to one, will enable CMDQ mode back on.

Luca Porzio (2):
  Remove unnecessary usage of use_cqe parameter in mmc_queue and use
    more appropriate mmc_host->cqe_enabled
  Make cmdq_en attribute in sysfs, writeable. When 0 is written:     -
    CMDQ is disabled and kept disabled across device reboots. When 1 is
    written:     - CMDQ mode is instantly reneabled (if supported).

 drivers/mmc/core/block.c |   7 +-
 drivers/mmc/core/mmc.c   | 152 ++++++++++++++++++++++++++++++---------
 drivers/mmc/core/queue.c |  11 ++-
 drivers/mmc/core/queue.h |   1 -
 include/linux/mmc/card.h |   1 +
 5 files changed, 127 insertions(+), 45 deletions(-)