From: Thara Gopinath <thara.gopinath@linaro.org>
To: mdalam@codeaurora.org
Cc: vkoul@kernel.org, corbet@lwn.net, agross@kernel.org,
bjorn.andersson@linaro.org, dan.j.williams@intel.com,
dmaengine@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
sricharan@codeaurora.org
Subject: Re: [PATCH] dmaengine: qcom: bam_dma: Add LOCK and UNLOCK flag bit support
Date: Mon, 21 Dec 2020 13:09:50 -0500 [thread overview]
Message-ID: <8c86f4db-9956-10d1-b380-a207137b50ef@linaro.org> (raw)
In-Reply-To: <9769c54acf54617a17346fea60ee38b6@codeaurora.org>
On 12/21/20 2:35 AM, mdalam@codeaurora.org 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
next prev parent reply other threads:[~2020-12-21 18:10 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 14:37 [PATCH] dmaengine: qcom: bam_dma: Add LOCK and UNLOCK flag bit support Md Sadre Alam
2020-12-19 3:35 ` Thara Gopinath
2020-12-21 7:35 ` mdalam
2020-12-21 18:09 ` Thara Gopinath [this message]
2020-12-22 12:18 ` mdalam
2021-01-12 9:30 ` mdalam
2020-12-21 9:23 ` Vinod Koul
2020-12-21 17:33 ` mdalam
2021-01-12 9:31 ` mdalam
2021-01-12 10:10 ` Vinod Koul
2021-01-13 19:50 ` mdalam
2021-01-15 5:58 ` Vinod Koul
2021-01-18 3:51 ` mdalam
2021-01-19 16:45 ` Vinod Koul
2021-01-27 18:26 ` mdalam
2021-02-01 6:05 ` Vinod Koul
2021-02-01 6:22 ` mdalam
2021-02-01 6:43 ` Vinod Koul
2021-02-01 15:50 ` mdalam
2021-02-09 16:39 ` mdalam
2021-02-09 17:35 ` Bjorn Andersson
2021-02-11 4:01 ` mdalam
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