linux-kernel - Re: [PATCH] dmaengine: imx-sdma: Add device to device support

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Date:	Tue, 7 Jul 2015 09:50:57 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Shengjiu Wang <shengjiu.wang@...escale.com>
Cc:	dan.j.williams@...el.com, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: imx-sdma: Add device to device support

On Tue, Jun 23, 2015 at 04:42:54PM +0800, Shengjiu Wang wrote:
> +static void sdma_set_watermarklevel_for_p2p(struct sdma_channel *sdmac)
> +{
> +	struct sdma_engine *sdma = sdmac->sdma;
> +
> +	int lwml = sdmac->watermark_level & 0xff;
> +	int hwml = (sdmac->watermark_level >> 16) & 0xff;
> +
> +	if (sdmac->event_id0 > 31) {
> +		sdmac->event_mask[0] |= 0;
> +		__set_bit(28, &sdmac->watermark_level);
why not use set_bit(), you are modifying driver memory


> +		sdmac->event_mask[1] |=
> +				BIT(sdmac->event_id0 % 32);
and then why not use set_bit() here too?

> +	} else {
> +		sdmac->event_mask[0] |= 0;
> +		sdmac->event_mask[1] |=
> +				BIT(sdmac->event_id0 % 32);
> +	}
> +	if (sdmac->event_id1 > 31) {
> +		sdmac->event_mask[1] |= 0;
> +		__set_bit(29, &sdmac->watermark_level);
> +		sdmac->event_mask[0] |=
> +			BIT(sdmac->event_id1 % 32);
> +	} else {
> +		sdmac->event_mask[1] |= 0;
> +		sdmac->event_mask[0] |=
> +			BIT(sdmac->event_id1 % 32);
> +	}
pattern for eventidX is repeated, also in that we can make generic macro to
handle and reduce code size

> +
> +	/*
> +	 * If LWML(src_maxburst) > HWML(dst_maxburst), we need
> +	 * swap LWML and HWML of INFO(A.3.2.5.1), also need swap
> +	 * r0(event_mask[1]) and r1(event_mask[0]).
> +	 */
> +	if (lwml > hwml) {
> +		sdmac->watermark_level &= ~0xff00ff;
Magic number?

>  static int sdma_config_channel(struct dma_chan *chan)
>  {
>  	struct sdma_channel *sdmac = to_sdma_chan(chan);
> @@ -869,6 +945,12 @@ static int sdma_config_channel(struct dma_chan *chan)
>  		sdma_event_enable(sdmac, sdmac->event_id0);
>  	}
>  
> +	if (sdmac->event_id1) {
> +		if (sdmac->event_id1 >= sdmac->sdma->drvdata->num_events)
> +			return -EINVAL;
> +		sdma_event_enable(sdmac, sdmac->event_id1);
> +	}
> +
>  	switch (sdmac->peripheral_type) {
>  	case IMX_DMATYPE_DSP:
>  		sdma_config_ownership(sdmac, false, true, true);
> @@ -887,19 +969,21 @@ static int sdma_config_channel(struct dma_chan *chan)
>  			(sdmac->peripheral_type != IMX_DMATYPE_DSP)) {
>  		/* Handle multiple event channels differently */
>  		if (sdmac->event_id1) {
> -			sdmac->event_mask[1] = BIT(sdmac->event_id1 % 32);
> -			if (sdmac->event_id1 > 31)
> -				__set_bit(31, &sdmac->watermark_level);
> -			sdmac->event_mask[0] = BIT(sdmac->event_id0 % 32);
> -			if (sdmac->event_id0 > 31)
> -				__set_bit(30, &sdmac->watermark_level);
> -		} else {
> +			if (sdmac->peripheral_type == IMX_DMATYPE_ASRC_SP ||
> +			    sdmac->peripheral_type == IMX_DMATYPE_ASRC)
> +				sdma_set_watermarklevel_for_p2p(sdmac);
> +		} else
>  			__set_bit(sdmac->event_id0, sdmac->event_mask);
> -		}
> +
>  		/* Watermark Level */
>  		sdmac->watermark_level |= sdmac->watermark_level;
>  		/* Address */
> -		sdmac->shp_addr = sdmac->per_address;
> +		if (sdmac->direction == DMA_DEV_TO_DEV) {
Okay the direction is depreciated, so can you store both source and
destination and use them based on direction in prepare()

Also I see driver is not doing this, so while at it, can you fix this is
current code as well

-- 
~Vinod

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