Re: [PATCH] dmaengine: qcom: bam_dma: Add LOCK and UNLOCK flag bit support

[Thara Gopinath]

On 12/21/20 2:35 AM, mdalam@xxxxxxxxxxxxxx wrote:
> On 2020-12-19 09:05, Thara Gopinath wrote:
> > On 12/17/20 9:37 AM, 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.
> > Hi,
> >
> > This is a generic question. What is the point of LOCK/UNLOCK with
> > allocating LOCK groups to the individual dma channels? By default
> > doesn't all channels fall in the same group. This would mean that
> > a lock does not prevent the dma controller from not executing a
> > transaction on the other channels.
>
> The Pipe Locking/Unlocking will be only on command-descriptor.
> Upon encountering a command 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.

So unless you assign pipe groups, this will not work as intended right? 
So this patch is only half of the solution. There should also be a patch 
allowing pipe groups to be assigned. Without that extra bit this patch 
does nothing , right ?


--
Warm Regards
Thara