On 2021-02-01 21:20, mdalam@codeaurora.org wrote:

On 2021-02-01 12:13, Vinod Koul wrote:

quoted

On 01-02-21, 11:52, mdalam@codeaurora.org wrote:

quoted

On 2021-02-01 11:35, Vinod Koul wrote:

quoted

On 27-01-21, 23:56, mdalam@codeaurora.org wrote:

quoted

quoted

quoted

  The actual LOCK/UNLOCK flag should be set on hardware command
descriptor.
  so this flag setting should be done in DMA engine driver. The user
of the
DMA
  driver like (in case of IPQ5018) Crypto can use flag
"DMA_PREP_LOCK" &
"DMA_PREP_UNLOCK"
  while preparing CMD descriptor before submitting to the DMA
engine. In DMA
engine driver
  we are checking these flasgs on CMD descriptor and setting actual
LOCK/UNLOCK flag on hardware
  descriptor.

I am not sure I comprehend this yet.. when is that we would need to do
this... is this for each txn submitted to dmaengine.. or something
else..

 Its not for each transaction submitted to dmaengine. We have to set 
this
only
 once on CMD descriptor. So when A53 crypto driver need to change the 
crypto
configuration
 then first it will lock the all other pipes using setting the LOCK 
flag bit
on CMD
 descriptor and then it can start the transaction , on data 
descriptor this
flag will
 not get set once all transaction will be completed the A53 crypto 
driver
release the lock on
 all other pipes using UNLOCK flag on CMD descriptor. So LOCK/UNLOCK 
will be
only once and not for
 the each transaction.

Okay so why cant the bam driver check cmd descriptor and do 
lock/unlock
as below, why do we need users to do this.

        if (flags & DMA_PREP_CMD) {
                do_lock_bam();

 User will not decide to do this LOCK/UNLOCK mechanism. It depends on 
use case.
 This LOCK/UNLOCK mechanism not required always. It needs only when
hardware will be shared
 between different core with different driver.
 The LOCK/UNLOCK flags provides SW to enter ordering between pipes 
execution.
 (Generally, the BAM pipes are total independent from each other and
work in parallel manner).
 This LOCK/UNLOCK flags are part of actual pipe hardware descriptor.

 Pipe descriptor having the following flags:
 INT : Interrupt
 EOT: End of transfer
 EOB: End of block
 NWD: Notify when done
 CMD: Command
 LOCK: Lock
 UNLOCK: Unlock
 etc.

 Here the BAM driver is common driver for (QPIC, Crypto, QUP etc. in 
IPQ5018)
 So here only Crypto will be shared b/w multiple cores so For crypto
request only the LOCK/UNLOCK
 mechanism required.
 For other request like for QPIC driver, QUPT driver etc. its not
required. So Crypto driver has to raise the flag for
 LOCK/UNLOCK while preparing CMD descriptor. The actual locking will
happen in BAM driver only using condition
 if (flags & DMA_PREP_CMD) {
     if (flags & DMA_PREP_LOCK)
        desc->flags |= cpu_to_le16(DESC_FLAG_LOCK);
 }

 So Crypto driver should set this flag DMA_PREP_LOCK while preparing
CMD descriptor.
 So LOCK should be set on actual hardware pipe descriptor with
descriptor type CMD.

quoted

The point here is that this seems to be internal to dma and should be
handled by dma driver.

  This LOCK/UNLOK flags are part of actual hardware descriptor so this
should be handled by BAM driver only.
  If we set condition like this
  if (flags & DMA_PREP_CMD) {
                do_lock_bam();
  Then LOCK/UNLOCK will be applied for all the CMD descriptor
including (QPIC driver, QUP driver , Crypto driver etc.).
  So this is not our intension. So we need to set this LOCK/UNLOCK
only for the drivers it needs. So Crypto driver needs
  locking mechanism so we will set LOCK/UNLOCK flag on Crypto driver
request only for other driver request like QPIC driver,
  QUP driver will not set this.

    ping! Do you need any further info on this?

quoted

Also if we do this, it needs to be done for specific platforms..

quoted

Thanks