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

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Message-ID: <37b059dcb67d1c83c2193acecef0ab96@codeaurora.org>
Date:   Fri, 19 Aug 2016 07:13:43 -0400
From:   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 2016-08-19 01:52, Vinod Koul wrote:
> On Thu, Aug 18, 2016 at 11:48:52PM -0400, Sinan Kaya wrote:
>> 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.
> 
> You didn't answer my question!
> 
> On error you said you flush, so who does that?

This is done by the driver in interrupt context when an error interrupt 
is received. All transactions are posted and hw is reset.

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