scsi: ufs: add support for query requests
Add support for sending UFS query requests through tagged command
queuing. This design allows queuing query requests in any open slot
along with other SCSI commands. In this way there is no need to
save a slot in the requests queue and decrease its size.
A query request is posing to a SCSI command to use native flow. But
unlike normal SCSI command flow, the data and response fields are
filled in UFS host data structure instead of passing as arguments
while queuing into SCSI mlqueue (mid-layer SCSI queue, the requests
from this queue are submitted to the device queue). As per specification
only one query request is allowed to be processed by device. Hence a
mutex lock for protecting data and response fields (hba->query.request and
hba->query.response) needs to be held while query request is in
progress.
The API for submitting a query request is ufs_query_request() in
ufshcd.c. This function is responsible for:
1. Obtaining the SCSI device from the host
2. Keeping the query mutex to prevent multiple queries
3. Storing the required data for sending a query request in ufs_hba
4. Queuing a SCSI vendor specific command to trigger a query request
in the UFS driver.
The callers of ufs_query_request() are expected to fill the query
command data fields and are to provide an allocated response field
for the driver to fill response fields after request completion.
The request and response upiu is extended in a union to enable using the
same data structure, both for command upiu and query request upiu.
The query request flow is separated from the scsi command flow in:
1. Preparing the request
2. Validating response (error) codes
3. Copying data (only used for descriptor read/write query requests)
4. Copying response/sense
Data error can't be handled in the scsi command native flow. Hence,
we pass the code as without a change back to the submitting layer.
UPIU (UFS Protocol Information Unit) size is increased to 512 bytes
from 128. The UPIU header and the transaction specific fields (SCSI
command or Query Request OSF - Op-code Specific Fields) are 32 bytes
together, the rest is used to transfer extra request data (such as
descriptor in query requests). In order to accommodate the largest
descriptor in the UFS spec (256 bytes) we need to increase the UPIU
size.
Change-Id: I997701888b53366e5bdcfd47df8a5a262a46470f
Signed-off-by: Dolev Raviv <draviv@codeaurora.org>
4 files changed