linux-kernel - Re: [PATCH v2 2/2] dmaengine: hdmac: Add scatter-gathered memset support

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Date:	Thu, 22 Oct 2015 12:18:51 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
CC:	<dmaengine@...r.kernel.org>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] dmaengine: hdmac: Add scatter-gathered memset
 support

Le 22/10/2015 11:41, Maxime Ripard a écrit :
> Just like memset support, the HDMAC might be used to do a memset over a
> discontiguous memory area.
> 
> In such a case, we'll just build up a chain of memset descriptors over the
> contiguous chunks of memory to set, in order to allow such a support.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>

Yep, seems good!
Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>

Thanks Maxime, bye.


> ---
>  drivers/dma/at_hdmac.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 79 insertions(+)
> 
> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
> index cad18f3660ae..4e55239c7a30 100644
> --- a/drivers/dma/at_hdmac.c
> +++ b/drivers/dma/at_hdmac.c
> @@ -986,6 +986,83 @@ err_free_buffer:
>  	return NULL;
>  }
>  
> +static struct dma_async_tx_descriptor *
> +atc_prep_dma_memset_sg(struct dma_chan *chan,
> +		       struct scatterlist *sgl,
> +		       unsigned int sg_len, int value,
> +		       unsigned long flags)
> +{
> +	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
> +	struct at_dma		*atdma = to_at_dma(chan->device);
> +	struct at_desc		*desc = NULL, *first = NULL, *prev = NULL;
> +	struct scatterlist	*sg;
> +	void __iomem		*vaddr;
> +	dma_addr_t		paddr;
> +	size_t			total_len = 0;
> +	int			i;
> +
> +	dev_vdbg(chan2dev(chan), "%s: v0x%x l0x%zx f0x%lx\n", __func__,
> +		 value, sg_len, flags);
> +
> +	if (unlikely(!sgl || !sg_len)) {
> +		dev_dbg(chan2dev(chan), "%s: scatterlist is empty!\n",
> +			__func__);
> +		return NULL;
> +	}
> +
> +	vaddr = dma_pool_alloc(atdma->memset_pool, GFP_ATOMIC, &paddr);
> +	if (!vaddr) {
> +		dev_err(chan2dev(chan), "%s: couldn't allocate buffer\n",
> +			__func__);
> +		return NULL;
> +	}
> +	*(u32*)vaddr = value;
> +
> +	for_each_sg(sgl, sg, sg_len, i) {
> +		dma_addr_t dest = sg_dma_address(sg);
> +		size_t len = sg_dma_len(sg);
> +
> +		dev_vdbg(chan2dev(chan), "%s: d0x%08x, l0x%zx\n",
> +			 __func__, dest, len);
> +
> +		if (!is_dma_fill_aligned(chan->device, dest, 0, len)) {
> +			dev_err(chan2dev(chan), "%s: buffer is not aligned\n",
> +				__func__);
> +			goto err_put_desc;
> +		}
> +
> +		desc = atc_create_memset_desc(chan, paddr, dest, len);
> +		if (!desc)
> +			goto err_put_desc;
> +
> +		atc_desc_chain(&first, &prev, desc);
> +
> +		total_len += len;
> +	}
> +
> +	/*
> +	 * Only set the buffer pointers on the last descriptor to
> +	 * avoid free'ing while we have our transfer still going
> +	 */
> +	desc->memset_paddr = paddr;
> +	desc->memset_vaddr = vaddr;
> +	desc->memset_buffer = true;
> +
> +	first->txd.cookie = -EBUSY;
> +	first->total_len = total_len;
> +
> +	/* set end-of-link on the descriptor */
> +	set_desc_eol(desc);
> +
> +	first->txd.flags = flags;
> +
> +	return &first->txd;
> +
> +err_put_desc:
> +	atc_desc_put(atchan, first);
> +	return NULL;
> +}
> +
>  /**
>   * atc_prep_slave_sg - prepare descriptors for a DMA_SLAVE transaction
>   * @chan: DMA channel
> @@ -1868,6 +1945,7 @@ static int __init at_dma_probe(struct platform_device *pdev)
>  	dma_cap_set(DMA_INTERLEAVE, at91sam9g45_config.cap_mask);
>  	dma_cap_set(DMA_MEMCPY, at91sam9g45_config.cap_mask);
>  	dma_cap_set(DMA_MEMSET, at91sam9g45_config.cap_mask);
> +	dma_cap_set(DMA_MEMSET_SG, at91sam9g45_config.cap_mask);
>  	dma_cap_set(DMA_PRIVATE, at91sam9g45_config.cap_mask);
>  	dma_cap_set(DMA_SLAVE, at91sam9g45_config.cap_mask);
>  	dma_cap_set(DMA_SG, at91sam9g45_config.cap_mask);
> @@ -1989,6 +2067,7 @@ static int __init at_dma_probe(struct platform_device *pdev)
>  
>  	if (dma_has_cap(DMA_MEMSET, atdma->dma_common.cap_mask)) {
>  		atdma->dma_common.device_prep_dma_memset = atc_prep_dma_memset;
> +		atdma->dma_common.device_prep_dma_memset_sg = atc_prep_dma_memset_sg;
>  		atdma->dma_common.fill_align = DMAENGINE_ALIGN_4_BYTES;
>  	}
>  
> 


-- 
Nicolas Ferre
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