linux-kernel - Re: [PATCH V2] dmaengine: imx-sdma: Add device to device support

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Date:	Fri, 10 Jul 2015 13:28:07 +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 V2] dmaengine: imx-sdma: Add device to device support

On Tue, Jul 07, 2015 at 05:20:04PM +0800, Shengjiu Wang wrote:

> +/*
> + *  p_2_p watermark_level description
> + *	Bits		Name			Description
> + *	0-7		Lower WML		Lower watermark level
> + *	8		PS			1: Pad Swallowing
> + *						0: No Pad Swallowing
> + *	9		PA			1: Pad Adding
> + *						0: No Pad Adding
> + * 	10		SPDIF			If this bit is set both source
> + *						and destination are on SPBA
> + *	11		Source Bit(SP)		1: Source on SPBA
> + *						0: Source on AIPS
> + *	12		Destination Bit(DP)	1: Destination on SPBA
> + *						0: Destination on AIPS
> + *	13-15		---------		MUST BE 0
> + *	16-23		Higher WML		HWML
> + *	24-27		N			Total number of samples after
> + *						which Pad adding/Swallowing
> + *						must be done. It must be odd.
> + *	28		Lower WML Event(LWE)	SDMA events reg to check for
> + *						LWML event mask
> + *						0: LWE in EVENTS register
> + *						1: LWE in EVENTS2 register
> + *	29		Higher WML Event(HWE)	SDMA events reg to check for
> + *						HWML event mask
> + *						0: HWE in EVENTS register
> + *						1: HWE in EVENTS2 register
> + *	30		---------		MUST BE 0
> + *	31		CONT			1: Amount of samples to be
> + *						transferred is unknown and
> + *						script will keep on
> + *						transferring samples as long as
> + *						both events are detected and
> + *						script must be manually stopped
> + *						by the application
> + *						0: The amount of samples to be
> + *						transferred is equal to the
> + *						count field of mode word
> + */
> +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;
> +
> +	__set_bit(sdmac->event_id0 % 32, &sdmac->event_mask[1]);
> +	__set_bit(sdmac->event_id1 % 32, &sdmac->event_mask[0]);
> +
> +	if (sdmac->event_id0 > 31)
> +		__set_bit(28, &sdmac->watermark_level);
> +
> +	if (sdmac->event_id1 > 31)
> +		__set_bit(29, &sdmac->watermark_level);
> +
> +	/*
> +	 * 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;
> +		sdmac->watermark_level |= hwml;
> +		sdmac->watermark_level |= lwml << 16;
> +		swap(sdmac->event_mask[0], sdmac->event_mask[1]);
so typical practice is to define macros for these. For example above can be
defined as
#define SDMA_WATERMARK_LWML BIT(X)
#define SDMA_WATERMARK_PA BIT(Y)

Then here you can say
	sdmac->watermark_level &= SDMA_WATERMARK_PA | ....

That way it is easier to read, review and maintain


> +	}
> +
> +	if (sdmac->per_address2 >= sdma->spba_start_addr &&
> +			sdmac->per_address2 <= sdma->spba_end_addr)
> +		__set_bit(11, &sdmac->watermark_level);
> +
> +	if (sdmac->per_address >= sdma->spba_start_addr &&
> +			sdmac->per_address <= sdma->spba_end_addr)
> +		__set_bit(12, &sdmac->watermark_level);
> +
> +	__set_bit(31, &sdmac->watermark_level);
All these and few more below will look much better by have defines above

> @@ -1221,6 +1311,14 @@ static int sdma_config(struct dma_chan *chan,
>  		sdmac->watermark_level = dmaengine_cfg->src_maxburst *
>  			dmaengine_cfg->src_addr_width;
>  		sdmac->word_size = dmaengine_cfg->src_addr_width;
> +	} else if (dmaengine_cfg->direction == DMA_DEV_TO_DEV) {
> +		sdmac->per_address2 = dmaengine_cfg->src_addr;
> +		sdmac->per_address = dmaengine_cfg->dst_addr;
> +		sdmac->watermark_level =
> +			dmaengine_cfg->src_maxburst & 0xff;
> +		sdmac->watermark_level |=
> +			(dmaengine_cfg->dst_maxburst & 0xff) << 16;
> +		sdmac->word_size = dmaengine_cfg->dst_addr_width;
Please fix this as well

-- 
~Vinod
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