linux-kernel - Re: [PATCH char-misc-next 11/19] dma: Add support to program MIC x100 status descriptiors

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Date:	Thu, 20 Aug 2015 10:50:14 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Ashutosh Dixit <ashutosh.dixit@...el.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dan Williams <dan.j.williams@...el.com>,
	linux-kernel@...r.kernel.org, Sudeep Dutt <sudeep.dutt@...el.com>,
	Nikhil Rao <nikhil.rao@...el.com>,
	Siva Yerramreddy <yshivakrishna@...il.com>
Subject: Re: [PATCH char-misc-next 11/19] dma: Add support to program MIC
 x100 status descriptiors

On Mon, Jul 27, 2015 at 04:58:17PM -0700, Ashutosh Dixit wrote:
> +/* Program a status descriptor with phys as address and value to be written */
> +static int mic_dma_do_status_update(struct mic_dma_chan *ch, dma_addr_t phys,
> +				    u64 value)
> +{
> +	int ret = mic_dma_avail_desc_ring_space(ch, 4);
> +
> +	if (ret < 0)
> +		return ret;
> +	ret = 0;
?
> +	mic_dma_prep_status_desc(&ch->desc_ring[ch->head],
> +				 value, phys, false);
> +	mic_dma_hw_ring_inc_head(ch);
> +	return ret;

return 0 then?

> +}
> +
>  static inline void mic_dma_issue_pending(struct dma_chan *ch)
>  {
>  	struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
> @@ -287,9 +310,28 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
>  		return NULL;
>  
>  	spin_lock(&mic_ch->prep_lock);
> +	if (len == 8) {
magic number?

> +		/*
> +		 * This is a hack to program status descriptor since
> +		 * DMA engine API doesn't have support for this.
> +		 */
what do you mean by programming status descriptor, what do you need to
program?

-- 
~Vinod

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