On 12-01-21, 15:01, mdalam@xxxxxxxxxxxxxx wrote:
On 2020-12-21 23:03, mdalam@xxxxxxxxxxxxxx wrote:
> On 2020-12-21 14:53, Vinod Koul wrote:
> > Hello,
> >
> > On 17-12-20, 20:07, Md Sadre Alam wrote:
> > > This change will add support for LOCK & UNLOCK flag bit support
> > > on CMD descriptor.
> > >
> > > If DMA_PREP_LOCK flag passed in prep_slave_sg then requester of this
> > > transaction wanted to lock the DMA controller for this transaction so
> > > BAM driver should set LOCK bit for the HW descriptor.
> > >
> > > If DMA_PREP_UNLOCK flag passed in prep_slave_sg then requester
> > > of this
> > > transaction wanted to unlock the DMA controller.so BAM driver
> > > should set
> > > UNLOCK bit for the HW descriptor.
> >
> > Can you explain why would we need to first lock and then unlock..? How
> > would this be used in real world.
> >
> > I have read a bit of documentation but is unclear to me. Also should
> > this be exposed as an API to users, sounds like internal to driver..?
> >
>
> IPQ5018 SoC having only one Crypto Hardware Engine. This Crypto Hardware
> Engine
> will be shared between A53 core & ubi32 core. There is two separate
> driver dedicated
> to A53 core and ubi32 core. So to use Crypto Hardware Engine
> parallelly for encryption/description
> we need bam locking mechanism. if one driver will submit the request
> for encryption/description
> to Crypto then first it has to set LOCK flag bit on command descriptor
> so that other pipes will
> get locked.
>
> The Pipe Locking/Unlocking will be only on command-descriptor. Upon
> encountering a command descriptor
Can you explain what is a cmd descriptor?
> with LOCK bit set, The BAM will lock all other pipes not related to
> the current pipe group, and keep
> handling the current pipe only until it sees the UNLOCK set then it
> will release all locked pipes.
> locked pipe will not fetch new descriptors even if it got event/events
> adding more descriptors for
> this pipe (locked pipe).
>
> No need to expose as an API to user because its internal to driver, so
> while preparing command descriptor
> just we have to update the LOCK/UNLOCK flag.
So IIUC, no api right? it would be internal to driver..?