linux-kernel - Re: [PATCH v4 02/14] dmaengine: tegra-apb: Implement synchronization callback

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Date:   Wed, 15 Jan 2020 10:25:45 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
CC:     <dmaengine@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 02/14] dmaengine: tegra-apb: Implement synchronization
 callback


On 15/01/2020 09:18, Jon Hunter wrote:
> 
> On 14/01/2020 21:02, Dmitry Osipenko wrote:
>> 14.01.2020 18:15, Jon Hunter пишет:
>>>
>>> On 12/01/2020 17:29, Dmitry Osipenko wrote:
>>>> The ISR tasklet could be kept scheduled after DMA transfer termination,
>>>> let's add synchronization callback which blocks until tasklet is finished.
>>>>
>>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>>> ---
>>>>  drivers/dma/tegra20-apb-dma.c | 8 ++++++++
>>>>  1 file changed, 8 insertions(+)
>>>>
>>>> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
>>>> index 319f31d27014..664e9c5df3ba 100644
>>>> --- a/drivers/dma/tegra20-apb-dma.c
>>>> +++ b/drivers/dma/tegra20-apb-dma.c
>>>> @@ -798,6 +798,13 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
>>>>  	return 0;
>>>>  }
>>>>  
>>>> +static void tegra_dma_synchronize(struct dma_chan *dc)
>>>> +{
>>>> +	struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
>>>> +
>>>> +	tasklet_kill(&tdc->tasklet);
>>>> +}
>>>> +
>>>
>>> Wouldn't there need to be some clean-up here? If the tasklet is
>>> scheduled, seems that there would be some other house-keeping that needs
>>> to be done after killing it.
>>
>> I'm not seeing anything to clean-up, could you please clarify?
> 
> Clean-up with regard to the descriptors. I was concerned if you will the
> tasklet the necessary clean-up of the descriptors is not handled.

Ah I see that tasklet_kill, unlike tasklet_kill_immediate, does wait for
the tasklet to run if scheduled. OK, then this should be fine.

Acked-by: Jon Hunter <jonathanh@...dia.com>

Cheers
Jon

-- 
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