lkml.org 
[lkml]   [2021]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] dmaengine: qcom: bam_dma: Add LOCK and UNLOCK flag bit support
On 2021-02-01 21:20, mdalam@codeaurora.org wrote:
> On 2021-02-01 12:13, Vinod Koul wrote:
>> On 01-02-21, 11:52, mdalam@codeaurora.org wrote:
>>> On 2021-02-01 11:35, Vinod Koul wrote:
>>> > On 27-01-21, 23:56, mdalam@codeaurora.org wrote:
>>
>>> > > 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.
>
>>
>> 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?

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

\
 
 \ /
  Last update: 2021-02-09 17:42    [W:4.084 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site