[RFC,1/5] dmaengine: Add support for reporting DMA cached data amount

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

On 2018-10-09 13:47, Vinod wrote:
> On 24-09-18, 16:00, 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
> 
> this looks okay to me, but not really up for 'cached', better
> alternates?

It is after all the amount of bytes cached within the DMA fabric, but I
agree it is a bit awkward.

Recently I tried to come up with something better, but did not went too
far...
dma_cached_bytes?
dma_held_bytes?
in_flight_bytes?
not_in_source_but_not_yet_in_destination_bytes :D ?

I try to come up with something for the initial series.

> Also we need to update Documentation for this..

Sure, I tend to forget that.

> 
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
>> ---
>>  drivers/dma/dmaengine.h   | 7 +++++++
>>  include/linux/dmaengine.h | 2 ++
>>  2 files changed, 9 insertions(+)
>>
>> diff --git a/drivers/dma/dmaengine.h b/drivers/dma/dmaengine.h
>> index 501c0b063f85..80214270b70e 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->cached = 0;
>>  	}
>>  	return dma_async_is_complete(cookie, complete, used);
>>  }
>> @@ -87,6 +88,12 @@ static inline void dma_set_residue(struct dma_tx_state *state, u32 residue)
>>  		state->residue = residue;
>>  }
>>  
>> +static inline void dma_set_cached(struct dma_tx_state *state, u32 cached)
>> +{
>> +	if (state)
>> +		state->cached = cached;
>> +}
>> +
>>  struct dmaengine_desc_callback {
>>  	dma_async_tx_callback callback;
>>  	dma_async_tx_callback_result callback_result;
>> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
>> index 10ff71b13eef..16c9d021988a 100644
>> --- a/include/linux/dmaengine.h
>> +++ b/include/linux/dmaengine.h
>> @@ -701,11 +701,13 @@ static inline struct dma_async_tx_descriptor *txd_next(struct dma_async_tx_descr
>>   * @residue: the remaining number of bytes left to transmit
>>   *	on the selected transfer for states DMA_IN_PROGRESS and
>>   *	DMA_PAUSED if this is implemented in the driver, else 0
>> + * @cached: amount of data in bytes cached by the DMA.
>>   */
>>  struct dma_tx_state {
>>  	dma_cookie_t last;
>>  	dma_cookie_t used;
>>  	u32 residue;
>> +	u32 cached;
>>  };
>>  
>>  /**
>> -- 
>> Peter
>>
>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> 

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki