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

[Vinod Koul <vkoul@kernel.org>]

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?

Also we need to update Documentation for this..

> 
> 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
> 
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