linux-kernel - Re: [PATCH v7 05/12] dmaengine: Add support for reporting DMA cached data amount

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Date:   Fri, 20 Dec 2019 10:49:52 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Vinod Koul <vkoul@...nel.org>
CC:     <robh+dt@...nel.org>, <nm@...com>, <ssantosh@...nel.org>,
        <dan.j.williams@...el.com>, <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <grygorii.strashko@...com>, <lokeshvutla@...com>,
        <t-kristo@...com>, <tony@...mide.com>, <j-keerthy@...com>,
        <vigneshr@...com>
Subject: Re: [PATCH v7 05/12] dmaengine: Add support for reporting DMA cached
 data amount



On 20/12/2019 10.37, Vinod Koul wrote:
> On 09-12-19, 11:43, Peter Ujfalusi wrote:
>> A DMA hardware can have big cache or FIFO and the amount of data sitting in
>> the DMA fabric can be an interest for the clients.
>>
>> For example in audio we want to know the delay in the data flow and in case
>> the DMA have significantly large FIFO/cache, it can affect the latenc/delay
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
>> Reviewed-by: Tero Kristo <t-kristo@...com>
>> ---
>>  drivers/dma/dmaengine.h   | 8 ++++++++
>>  include/linux/dmaengine.h | 2 ++
>>  2 files changed, 10 insertions(+)
>>
>> diff --git a/drivers/dma/dmaengine.h b/drivers/dma/dmaengine.h
>> index 501c0b063f85..b0b97475707a 100644
>> --- a/drivers/dma/dmaengine.h
>> +++ b/drivers/dma/dmaengine.h
>> @@ -77,6 +77,7 @@ static inline enum dma_status dma_cookie_status(struct dma_chan *chan,
>>  		state->last = complete;
>>  		state->used = used;
>>  		state->residue = 0;
>> +		state->in_flight_bytes = 0;
>>  	}
>>  	return dma_async_is_complete(cookie, complete, used);
>>  }
>> @@ -87,6 +88,13 @@ static inline void dma_set_residue(struct dma_tx_state *state, u32 residue)
>>  		state->residue = residue;
>>  }
>>  
>> +static inline void dma_set_in_flight_bytes(struct dma_tx_state *state,
>> +					   u32 in_flight_bytes)
>> +{
>> +	if (state)
>> +		state->in_flight_bytes = in_flight_bytes;
>> +}
> 
> This would be used by dmaengine drivers right, so lets move it to drivers/dma/dmaengine.h
> 
> lets not expose this to users :)

I have put it where the dma_set_residue() was.
I can add a patch first to move dma_set_residue() then add
dma_set_in_flight_bytes() there as well?

- Péter

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