linux-kernel - Re: [PATCH_V3 2/3] dma: jz4780: add driver for the Ingenic JZ4780 DMA controller

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Date:	Mon, 16 Mar 2015 16:16:46 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Zubair Lutfullah Kakakhel <Zubair.Kakakhel@...tec.com>
Cc:	dan.j.williams@...el.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, alex@...x-smith.me.uk
Subject: Re: [PATCH_V3 2/3] dma: jz4780: add driver for the Ingenic JZ4780
 DMA controller

On Thu, Feb 26, 2015 at 12:43:33PM +0000, Zubair Lutfullah Kakakhel wrote:
> +/* Per-channel registers. */
> +#define JZ_DMA_REG_DSA(n)	(0x00 + (n) * 0x20)
> +#define JZ_DMA_REG_DTA(n)	(0x04 + (n) * 0x20)
> +#define JZ_DMA_REG_DTC(n)	(0x08 + (n) * 0x20)
> +#define JZ_DMA_REG_DRT(n)	(0x0c + (n) * 0x20)
> +#define JZ_DMA_REG_DCS(n)	(0x10 + (n) * 0x20)
> +#define JZ_DMA_REG_DCM(n)	(0x14 + (n) * 0x20)
> +#define JZ_DMA_REG_DDA(n)	(0x18 + (n) * 0x20)
> +#define JZ_DMA_REG_DSD(n)	(0x1c + (n) * 0x20)
shouldn't this be a macro rather than copy paste n * 0x20

> +
> +#define JZ_DMA_DMAC_DMAE	BIT(0)
> +#define JZ_DMA_DMAC_AR		BIT(2)
> +#define JZ_DMA_DMAC_HLT		BIT(3)
> +#define JZ_DMA_DMAC_FMSC	BIT(31)
> +
> +#define JZ_DMA_DRT_AUTO		0x8
not consistent in BIT?

> +static struct jz4780_dma_desc *jz4780_dma_desc_alloc(
> +	struct jz4780_dma_chan *jzchan, unsigned int count,
> +	enum dma_transaction_type type)
> +{
> +	struct jz4780_dma_desc *desc;
> +
> +	if (count > JZ_DMA_MAX_DESC)
> +		return NULL;
> +
> +	desc = kzalloc(sizeof(*desc), GFP_ATOMIC);
GFP_NOWAIT pls

> +	if (!desc)
> +		return NULL;
> +
> +	desc->desc = dma_pool_alloc(jzchan->desc_pool, GFP_ATOMIC,
ditto

> +static uint32_t jz4780_dma_width(enum dma_slave_buswidth width)
> +{
> +	switch (width) {
> +	case DMA_SLAVE_BUSWIDTH_1_BYTE:
> +		return JZ_DMA_WIDTH_8_BIT;
> +	case DMA_SLAVE_BUSWIDTH_2_BYTES:
> +		return JZ_DMA_WIDTH_16_BIT;
these are same as dmaengine defines so should this be:

	case DMA_SLAVE_BUSWIDTH_1_BYTE:
	case DMA_SLAVE_BUSWIDTH_2_BYTES:
		return width;
> +	default:
> +		return JZ_DMA_WIDTH_32_BIT;
> +	}
> +}
> +
> +static uint32_t jz4780_dma_transfer_size(unsigned long val, int *ord)
> +{
> +	*ord = ffs(val) - 1;
> +
> +	/* 8 byte transfer sizes unsupported so fall back on 4. */
okay falling back is not a good idea, same applies for default in
jz4780_dma_width(). The slave dma parameters are match with devices, so
programming something which you dont support, falling back or using defaults
is not a good idea

> +	default:
> +		WARN_ON(1);
> +		return -1; /* Can never happen. See previous comment */
-1?? what happened to kernel error codes?

> +	}
> +}
> +
> +static void jz4780_dma_setup_hwdesc(struct jz4780_dma_chan *jzchan,
> +	struct jz4780_dma_hwdesc *desc, dma_addr_t addr, size_t len)
> +{
> +	struct dma_slave_config *config = &jzchan->config;
> +	uint32_t width, maxburst, tsz;
> +	int ord;
> +
> +	if (config->direction == DMA_MEM_TO_DEV) {
this is a wrong idea, use the direction from the prep_ call

> +static enum dma_status jz4780_dma_tx_status(struct dma_chan *chan,
> +	dma_cookie_t cookie, struct dma_tx_state *txstate)
> +{
> +	struct jz4780_dma_chan *jzchan = to_jz4780_dma_chan(chan);
> +	struct virt_dma_desc *vdesc;
> +	enum dma_status status;
> +	unsigned long flags;
> +
> +	status = dma_cookie_status(chan, cookie, txstate);
> +	if (status == DMA_COMPLETE)
or if the txstate is NULL



-- 
~Vinod
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