linux-kernel - Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the callback

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Date:   Thu, 18 Aug 2016 23:48:52 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        linux-arm-msm@...r.kernel.org, timur@...eaurora.org,
        linux-kernel@...r.kernel.org,
        Christopher Covington <cov@...eaurora.org>,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the
 callback

On 8/18/2016 11:42 PM, Vinod Koul wrote:
> On Thu, Aug 18, 2016 at 11:26:28PM -0400, Sinan Kaya wrote:
>> On 8/18/2016 10:48 PM, Vinod Koul wrote:
>>>> Keep a size limited list with error cookies and flush them in terminate all?
>>> I think so, terminate_all anyway cleans up the channel. Btw what is the
>>> behaviour on error? Do you terminate or somthing else?
>>>
>>
>> On error, I flush all outstanding transactions with an error code and I reset
>> the channel. After the reset, the DMA channel is functional again. The client
>> doesn't need to shutdown anything.
> 
> You mean from the client context or driver?
> 

The client doesn't need to call device_free_chan_resources and device_terminate_all
to be specific. Client can certainly call these if it needs to but it is not
required to recover the channel.

After the reset in error condition, the client can continue issuing new requests
with tx_submit and device_issue_pending as usual.

-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.