Subject: [PATCH v4 3/3] dma: Add Freescale eDMA engine driver support

From: [email-masked] (Vinod Koul)
Date: Wed, 28 Aug 2013 13:47:42 +0530

On Fri, Aug 16, 2013 at 02:07:54PM +0800, Jingchang Lu wrote:
> Add Freescale enhanced direct memory(eDMA) controller support.
> The eDMA controller deploys DMAMUXs routing DMA request sources(slot)
> to eDMA channels.
> This module can be found on Vybrid and LS-1 SoCs.
> 
+ devicetree at vger.kernel.org, need the binding acked by DT folks...

> Signed-off-by: Alison Wang <[email-masked]>
> Signed-off-by: Jingchang Lu <[email-masked]>
> ---
> changes in v4:
>   using exact compatible string in binding document.
> 
> changes in v3:
>   handle all pending interrupt one time.
>   add protect lock on dma transfer complete handling.
>   change desc and tcd alloc flag to GFP_NOWAIT.
>   add sanity check and error messages.
> 
> changes in v2:
>   using generic dma-channels property instead of fsl,dma-channel.
>   rename the binding document to fsl-edma.txt.
> 
>  Documentation/devicetree/bindings/dma/fsl-edma.txt |  84 ++
>  drivers/dma/Kconfig                                |  10 +
>  drivers/dma/Makefile                               |   1 +
>  drivers/dma/fsl-edma.c                             | 855 +++++++++++++++++++++
>  4 files changed, 950 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/fsl-edma.txt
>  create mode 100644 drivers/dma/fsl-edma.c
> 
> diff --git a/Documentation/devicetree/bindings/dma/fsl-edma.txt b/Documentation/devicetree/bindings/dma/fsl-edma.txt
> new file mode 100644
> index 0000000..95159da
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/fsl-edma.txt
> @@ -0,0 +1,84 @@
> +* Freescale enhanced direct memory access(eDMA) Controller
> +
> +The eDMA engine deploys DMAMUXs routing request sources(slot) to
> +eDMA controller channels.
> +
> +* eDMA Controller
> +Required properties:
> +- compatible :
> +  - "fsl,vf610-edma" for eDMA used similar to that on Vybrid vf610 SoC
> +- reg : Should contain eDMA registers location and length
> +- interrupts : Should contain eDMA interrupt
> +- interrupt-names : Should be "edma-tx" for tx interrupt and
> +  "edma-err" for err interrupt
> +- #dma-cells : Must be <2>.
> +  The first cell specifies the DMAMUX ID. Specific request source
> +  can only be routed by specific DMAMUXs.
> +  the second cell specifies the request source(slot) ID.
> +  See include/dt-bindings/dma/<soc>-edma.h for all the supported
> +  request source IDs.
> +- dma-channels : Number of channels supported by the controller
> +- fsl,dma-mux : Phandle of the DMAMUXs deployed by the controller
> +
> +
> +* DMAMUX
> +Required properties:
> +- reg : Should contain DMAMUX registers location and length
> +- fsl,dmamux-id : DMAMUX ID. DMAMUX IDs are unique in each eDMA controller.
> +  inside one eDMA controller, specific request source can only be routed by
> +  one of its DMAMUXs.
> +  However Specific request source may be routed to different eDMA controller,
> +  thus all the DMAMUXs sharing a the same request sources have the same ID.
> +- clocks : Phandle of the clock used by the DMAMUX
> +- clock-names : The clock names
> +
> +Below is the eDMA controller and DMAMUX association, and DMAMUX IDs assignment
> +On Vybrid vf610 SoC, DMAMUX0 and DMAMU3 share the same request source group,
> +and DMAMUX1 and DMAMU2 share the same request source group.
> +
> +eDMA controller		DMAMUXs		DMAMUX ID
> +-------------------------------------------------
> +eDMA0			DMAMUX0		0
> +			DMAMUX1		1
> +
> +eDMA1			DMAMUX2		1
> +			DMAMUX3		0
> +
> +Examples:
> +
> +edma0: edma at 40018000 {
> +	#dma-cells = <2>;
> +	compatible = "fsl,vf610-edma";
> +	reg = <0x40018000 0x2000>;
> +	interrupts = <0 8 0x04>, <0 9 0x04>;
> +	interrupt-names = "edma-tx", "edma-err";
> +	dma-channels = <32>;
> +	fsl,edma-mux = <&dmamux0>, <&dmamux1>;
> +};
> +
> +dmamux0: dmamux at 40024000 {
> +	reg = <0x40024000 0x1000>;
> +	fsl,dmamux-id = <0>;
> +	clocks = <&clks VF610_CLK_DMAMUX0>;
> +	clock-names = "dmamux";
> +};
> +
> +
> +* DMA clients
> +DMA client drivers that uses the DMA function must use the format described
> +in the dma.txt file, using a three-cell specifier for each channel: a phandle
> +plus two integer cells as described above.
> +
> +Examples:
> +
> +sai2: sai at 40031000 {
> +	compatible = "fsl,vf610-sai";
> +	reg = <0x40031000 0x1000>;
> +	interrupts = <0 86 0x04>;
> +	clocks = <&clks VF610_CLK_SAI2>;
> +	clock-names = "sai";
> +	dma-names = "tx", "rx";
> +	dmas = <&edma0 0 VF610_EDMA_MUXID0_SAI2_TX>,
> +		<&edma0 0 VF610_EDMA_MUXID0_SAI2_RX>;
> +	status = "disabled";
> +};
> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
> index 6825957..f9a6e06 100644
> --- a/drivers/dma/Kconfig
> +++ b/drivers/dma/Kconfig
> @@ -300,6 +300,16 @@ config DMA_JZ4740
>  	select DMA_ENGINE
>  	select DMA_VIRTUAL_CHANNELS
>  
> +config FSL_EDMA
> +	tristate "Freescale eDMA engine support"
> +	depends on OF
> +	select DMA_ENGINE
> +	select DMA_VIRTUAL_CHANNELS
> +	help
> +	  Support the Freescale eDMA engine with DMAMUXs managing route
> +	  between request sources(slot) and eDMA engine channels.
> +	  This module can be found on Freescale Vybrid and LS-1 SoCs.
> +
>  config DMA_ENGINE
>  	bool
>  
> diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
> index 5e0f2ef..fcbbac9 100644
> --- a/drivers/dma/Makefile
> +++ b/drivers/dma/Makefile
> @@ -39,3 +39,4 @@ obj-$(CONFIG_MMP_TDMA) += mmp_tdma.o
>  obj-$(CONFIG_DMA_OMAP) += omap-dma.o
>  obj-$(CONFIG_MMP_PDMA) += mmp_pdma.o
>  obj-$(CONFIG_DMA_JZ4740) += dma-jz4740.o
> +obj-$(CONFIG_FSL_EDMA) += fsl-edma.o
> diff --git a/drivers/dma/fsl-edma.c b/drivers/dma/fsl-edma.c
> new file mode 100644
> index 0000000..5104e5e
> --- /dev/null
> +++ b/drivers/dma/fsl-edma.c
> @@ -0,0 +1,855 @@
> +/*
> + * drivers/dma/fsl-edma.c
> + *
> + * Copyright 2013 Freescale Semiconductor, Inc.
> + *
> + * Driver for the Freescale eDMA engine with DMAMUXs managing route between
> + * request sources(slot) and eDMA engine channels, this module can be found
> + * on some Vybrid and Layerscape SoCs.
> + *
> + * This program is free software; you can redistribute  it and/or modify it
> + * under  the terms of  the GNU General  Public License as published by the
> + * Free Software Foundation;  either version 2 of the  License, or (at your
> + * option) any later version.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/interrupt.h>
> +#include <linux/clk.h>
> +#include <linux/spinlock.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/slab.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_dma.h>
> +#include <linux/dmapool.h>
> +
> +#include "virt-dma.h"
> +
> +#define EDMA_CR			0x00
> +#define EDMA_ES			0x04
> +#define EDMA_ERQ		0x0C
> +#define EDMA_EEI		0x14
> +#define EDMA_SERQ		0x1B
> +#define EDMA_CERQ		0x1A
> +#define EDMA_SEEI		0x19
> +#define EDMA_CEEI		0x18
> +#define EDMA_CINT		0x1F
> +#define EDMA_CERR		0x1E
> +#define EDMA_SSRT		0x1D
> +#define EDMA_CDNE		0x1C
> +#define EDMA_INTR		0x24
> +#define EDMA_ERR		0x2C
> +
> +#define EDMA_TCD_SADDR(x)	(0x1000 + 32 * (x))
> +#define EDMA_TCD_SOFF(x)	(0x1004 + 32 * (x))
> +#define EDMA_TCD_ATTR(x)	(0x1006 + 32 * (x))
> +#define EDMA_TCD_NBYTES(x)	(0x1008 + 32 * (x))
> +#define EDMA_TCD_SLAST(x)	(0x100C + 32 * (x))
> +#define EDMA_TCD_DADDR(x)	(0x1010 + 32 * (x))
> +#define EDMA_TCD_DOFF(x)	(0x1014 + 32 * (x))
> +#define EDMA_TCD_CITER_ELINK(x)	(0x1016 + 32 * (x))
> +#define EDMA_TCD_CITER(x)	(0x1016 + 32 * (x))
> +#define EDMA_TCD_DLAST_SGA(x)	(0x1018 + 32 * (x))
> +#define EDMA_TCD_CSR(x)		(0x101C + 32 * (x))
> +#define EDMA_TCD_BITER_ELINK(x)	(0x101E + 32 * (x))
> +#define EDMA_TCD_BITER(x)	(0x101E + 32 * (x))
> +
> +#define EDMA_CR_EDBG		BIT(1)
> +#define EDMA_CR_ERCA		BIT(2)
> +#define EDMA_CR_ERGA		BIT(3)
> +#define EDMA_CR_HOE		BIT(4)
> +#define EDMA_CR_HALT		BIT(5)
> +#define EDMA_CR_CLM		BIT(6)
> +#define EDMA_CR_EMLM		BIT(7)
> +#define EDMA_CR_ECX		BIT(16)
> +#define EDMA_CR_CX		BIT(17)
> +
> +#define EDMA_SEEI_SEEI(x)	((x) & 0x1F)
> +#define EDMA_CEEI_CEEI(x)	((x) & 0x1F)
> +#define EDMA_CINT_CINT(x)	((x) & 0x1F)
> +#define EDMA_CERR_CERR(x)	((x) & 0x1F)
> +
> +#define EDMA_TCD_ATTR_DSIZE(x)		(((x) & 0x0007))
> +#define EDMA_TCD_ATTR_DMOD(x)		(((x) & 0x001F) << 3)
> +#define EDMA_TCD_ATTR_SSIZE(x)		(((x) & 0x0007) << 8)
> +#define EDMA_TCD_ATTR_SMOD(x)		(((x) & 0x001F) << 11)
> +#define EDMA_TCD_ATTR_SSIZE_8BIT	(0x0000)
> +#define EDMA_TCD_ATTR_SSIZE_16BIT	(0x0100)
> +#define EDMA_TCD_ATTR_SSIZE_32BIT	(0x0200)
> +#define EDMA_TCD_ATTR_SSIZE_64BIT	(0x0300)
> +#define EDMA_TCD_ATTR_SSIZE_32BYTE	(0x0500)
> +#define EDMA_TCD_ATTR_DSIZE_8BIT	(0x0000)
> +#define EDMA_TCD_ATTR_DSIZE_16BIT	(0x0001)
> +#define EDMA_TCD_ATTR_DSIZE_32BIT	(0x0002)
> +#define EDMA_TCD_ATTR_DSIZE_64BIT	(0x0003)
> +#define EDMA_TCD_ATTR_DSIZE_32BYTE	(0x0005)
> +
> +#define EDMA_TCD_CITER_MASK		0x7FFF
> +#define EDMA_TCD_BITER_MASK		0x7FFF
> +
> +#define EDMA_TCD_SOFF_SOFF(x)		(x)
> +#define EDMA_TCD_NBYTES_NBYTES(x)	(x)
> +#define EDMA_TCD_SLAST_SLAST(x)		(x)
> +#define EDMA_TCD_DADDR_DADDR(x)		(x)
> +#define EDMA_TCD_CITER_CITER(x)		((x) & 0x7FFF)
> +#define EDMA_TCD_DOFF_DOFF(x)		(x)
> +#define EDMA_TCD_DLAST_SGA_DLAST_SGA(x)	(x)
> +#define EDMA_TCD_BITER_BITER(x)		((x) & 0x7FFF)
> +
> +#define EDMA_TCD_CSR_START		BIT(0)
> +#define EDMA_TCD_CSR_INT_MAJOR		BIT(1)
> +#define EDMA_TCD_CSR_INT_HALF		BIT(2)
> +#define EDMA_TCD_CSR_D_REQ		BIT(3)
> +#define EDMA_TCD_CSR_E_SG		BIT(4)
> +#define EDMA_TCD_CSR_E_LINK		BIT(5)
> +#define EDMA_TCD_CSR_ACTIVE		BIT(6)
> +#define EDMA_TCD_CSR_DONE		BIT(7)
> +
> +#define EDMAMUX_CHCFG_DIS		0x0
> +#define EDMAMUX_CHCFG_ENBL		0x80
> +#define EDMAMUX_CHCFG_SOURCE(n)		((n) & 0x3F)
> +
> +struct fsl_edma_hw_tcd {
> +	u32	saddr;
> +	u16	soff;
> +	u16	attr;
> +	u32	nbytes;
> +	u32	slast;
> +	u32	daddr;
> +	u16	doff;
> +	u16	citer;
> +	u32	dlast_sga;
> +	u16	csr;
> +	u16	biter;
> +} __packed;
> +
> +struct fsl_edma_sw_tcd {
> +	dma_addr_t			ptcd;
> +	struct fsl_edma_hw_tcd		*vtcd;
> +};
> +
> +struct fsl_edma_slave_config {
> +	enum dma_transfer_direction	dir;
> +	enum dma_slave_buswidth		addr_width;
> +	u32				dev_addr;
> +	u32				burst;
> +	u32				attr;
> +};
> +
> +struct fsl_edma_dmamux {
> +	void __iomem			*membase;
> +	struct clk			*clk;
> +	u32				mux_id;
> +};
> +
> +struct fsl_edma_chan {
> +	struct virt_dma_chan		vchan;
> +	enum dma_status			status;
> +	struct fsl_edma_engine		*edma;
> +	struct fsl_edma_dmamux		*edmamux;
> +	struct fsl_edma_desc		*edesc;
> +
> +	u32				slot_id;
> +	struct fsl_edma_slave_config	fsc;
> +	struct dma_pool			*tcd_pool;
> +};
> +
> +struct fsl_edma_desc {
> +	struct virt_dma_desc		vdesc;
> +	struct fsl_edma_chan		*echan;
> +	bool				iscyclic;
> +	unsigned int			n_tcds;
> +	struct fsl_edma_sw_tcd		tcd[];
> +};
> +
> +struct fsl_edma_irq {
> +	int	txirq;
> +	int	errirq;
> +};
> +
> +struct fsl_edma_engine {
> +	struct dma_device	dma_dev;
> +	void __iomem		*membase;
> +	u32			n_chans;
> +	u32			n_muxes;
> +	struct fsl_edma_dmamux	*edmamux;
> +	struct fsl_edma_irq	edmairq;
> +	struct fsl_edma_chan	chans[];
> +};
> +
> +struct fsl_edma_filter_param {
> +	int	mux_id;
> +	int	slot_id;
> +};
> +
> +static inline struct fsl_edma_chan *to_fsl_edma_chan(struct dma_chan *chan)
> +{
> +	return container_of(chan, struct fsl_edma_chan, vchan.chan);
> +}
> +
> +static inline struct fsl_edma_desc *to_fsl_edma_desc(struct virt_dma_desc *vd)
> +{
> +	return container_of(vd, struct fsl_edma_desc, vdesc);
> +}
> +
> +static inline void fsl_edma_enable_request(struct fsl_edma_chan *fsl_chan)
> +{
> +	void __iomem *addr = fsl_chan->edma->membase;
> +	u32 ch = fsl_chan->vchan.chan.chan_id;
> +
> +	writeb(EDMA_SEEI_SEEI(ch), addr + EDMA_SEEI);
> +	writeb(ch, addr + EDMA_SERQ);
> +}
> +
> +static inline void fsl_edma_disable_request(struct fsl_edma_chan *fsl_chan)
> +{
> +	void __iomem *addr = fsl_chan->edma->membase;
> +	u32 ch = fsl_chan->vchan.chan.chan_id;
> +
> +	writeb(ch, addr + EDMA_CERQ);
> +	writeb(EDMA_CEEI_CEEI(ch), addr + EDMA_CEEI);
> +}
> +
> +static
> +void fsl_edmamux_config_chan(struct fsl_edma_chan *fsl_chan, unsigned char val)
> +{
> +	void __iomem *mux_addr = fsl_chan->edmamux->membase;
> +	unsigned chans_per_mux, ch;
> +
> +	chans_per_mux = fsl_chan->edma->n_chans / fsl_chan->edma->n_muxes;
> +	ch = fsl_chan->vchan.chan.chan_id % chans_per_mux;
> +
> +	writeb(val, mux_addr + ch);
> +}
> +
> +static unsigned int fsl_edma_get_tcd_attr(enum dma_slave_buswidth addr_width)
> +{
> +	switch (addr_width) {
> +	case 1:
> +		return EDMA_TCD_ATTR_SSIZE_8BIT | EDMA_TCD_ATTR_DSIZE_8BIT;
> +	case 2:
> +		return EDMA_TCD_ATTR_SSIZE_16BIT | EDMA_TCD_ATTR_DSIZE_16BIT;
> +	case 4:
> +		return EDMA_TCD_ATTR_SSIZE_32BIT | EDMA_TCD_ATTR_DSIZE_32BIT;
> +	case 8:
> +		return EDMA_TCD_ATTR_SSIZE_64BIT | EDMA_TCD_ATTR_DSIZE_64BIT;
> +	default:
> +		return EDMA_TCD_ATTR_SSIZE_32BIT | EDMA_TCD_ATTR_DSIZE_32BIT;
> +	}
> +}
> +
> +static void fsl_edma_free_desc(struct virt_dma_desc *vdesc)
> +{
> +	struct fsl_edma_desc *fsl_desc;
> +	int i;
> +
> +	fsl_desc = to_fsl_edma_desc(vdesc);
> +	for (i = 0; i < fsl_desc->n_tcds; i++)
> +			dma_pool_free(fsl_desc->echan->tcd_pool,
> +					fsl_desc->tcd[i].vtcd,
> +					fsl_desc->tcd[i].ptcd);
> +	kfree(fsl_desc);
> +}
> +
> +static int fsl_edma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> +		unsigned long arg)
> +{
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +	struct dma_slave_config *cfg = (void *)arg;
> +
> +	switch (cmd) {
> +	case DMA_TERMINATE_ALL:
> +		fsl_edma_disable_request(fsl_chan);
> +		fsl_chan->edesc = NULL;
> +		vchan_free_chan_resources(&fsl_chan->vchan);
> +		return 0;
> +
> +	case DMA_SLAVE_CONFIG:
> +		fsl_chan->fsc.dir = cfg->direction;
> +		if (cfg->direction == DMA_DEV_TO_MEM) {
> +			fsl_chan->fsc.dev_addr = cfg->src_addr;
> +			fsl_chan->fsc.addr_width = cfg->src_addr_width;
> +			fsl_chan->fsc.burst = cfg->src_maxburst;
> +			fsl_chan->fsc.attr = fsl_edma_get_tcd_attr(cfg->src_addr_width);
> +		} else if (cfg->direction == DMA_MEM_TO_DEV) {
> +			fsl_chan->fsc.dev_addr = cfg->dst_addr;
> +			fsl_chan->fsc.addr_width = cfg->dst_addr_width;
> +			fsl_chan->fsc.burst = cfg->dst_maxburst;
> +			fsl_chan->fsc.attr = fsl_edma_get_tcd_attr(cfg->dst_addr_width);
> +		} else {
since you support cyclic, is there a reasonw why you dont support pause/resume?
is it hw issue or planned in future?

> +			return -EINVAL;
> +		}
> +		return 0;
> +
> +	default:
> +		return -ENXIO;
> +	}
> +}
> +
> +static enum dma_status fsl_edma_tx_status(struct dma_chan *chan,
> +		dma_cookie_t cookie, struct dma_tx_state *txstate)
> +{
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +
> +	if (fsl_chan->status == DMA_ERROR)
> +		return DMA_ERROR;
> +
> +	return dma_cookie_status(chan, cookie, txstate);
this will tell if the DMA is completed or not only.
You also need to calculate residue for the pending dma

Since you support cyclic this should be done properly...

also you cna take more help from vchan support to make your life simpler...

> +}
> +
> +static void fsl_edma_set_tcd_params(struct fsl_edma_chan *fsl_chan,
> +		u32 src, u32 dst, u16 attr, u16 soff, u32 nbytes,
> +		u32 slast, u16 citer, u16 biter, u32 doff, u32 dlast_sga,
> +		u16 csr)
> +{
> +	void __iomem *addr = fsl_chan->edma->membase;
> +	u32 ch = fsl_chan->vchan.chan.chan_id;
> +
> +	writew(0, addr + EDMA_TCD_CSR(ch));
> +	writel(src, addr + EDMA_TCD_SADDR(ch));
> +	writel(dst, addr + EDMA_TCD_DADDR(ch));
> +	writew(attr, addr + EDMA_TCD_ATTR(ch));
> +	writew(EDMA_TCD_SOFF_SOFF(soff), addr + EDMA_TCD_SOFF(ch));
> +	writel(EDMA_TCD_NBYTES_NBYTES(nbytes), addr + EDMA_TCD_NBYTES(ch));
> +	writel(EDMA_TCD_SLAST_SLAST(slast), addr + EDMA_TCD_SLAST(ch));
> +	writew(EDMA_TCD_CITER_CITER(citer), addr + EDMA_TCD_CITER(ch));
> +	writew(EDMA_TCD_BITER_BITER(biter), addr + EDMA_TCD_BITER(ch));
> +	writew(EDMA_TCD_DOFF_DOFF(doff), addr + EDMA_TCD_DOFF(ch));
> +	writel(EDMA_TCD_DLAST_SGA_DLAST_SGA(dlast_sga),
> +					addr + EDMA_TCD_DLAST_SGA(ch));
> +	writew(csr, addr + EDMA_TCD_CSR(ch));
> +}
> +
> +static void fill_tcd_params(struct fsl_edma_hw_tcd *tcd, u32 src, u32 dst,
> +		u16 attr, u16 soff, u32 nbytes, u32 slast, u16 citer,
> +		u16 biter, u16 doff, u32 dlast_sga, bool major_int,
> +		bool disable_req, bool enable_sg)
> +{
> +	tcd->saddr = src;
> +	tcd->attr = attr;
> +	tcd->soff = soff;
> +	tcd->nbytes = nbytes;
> +	tcd->slast = slast;
> +	tcd->daddr = dst;
> +	tcd->citer = citer;
> +	tcd->doff = doff;
> +	tcd->dlast_sga = dlast_sga;
> +	tcd->biter = biter;
> +	tcd->csr = 0;
> +	if (major_int)
> +		tcd->csr |= EDMA_TCD_CSR_INT_MAJOR;
> +
> +	if (disable_req)
> +		tcd->csr |= EDMA_TCD_CSR_D_REQ;
> +
> +	if (enable_sg)
> +		tcd->csr |= EDMA_TCD_CSR_E_SG;
> +}
> +
> +static struct fsl_edma_desc *fsl_edma_alloc_desc(struct fsl_edma_chan *fsl_chan,
> +		int sg_len)
> +{
> +	struct fsl_edma_desc *fsl_desc;
> +	int i;
> +
> +	fsl_desc = kzalloc(sizeof(*fsl_desc) + sizeof(struct fsl_edma_sw_tcd) * sg_len,
> +				GFP_NOWAIT);
> +	if (!fsl_desc)
> +		return NULL;
> +
> +	fsl_desc->echan = fsl_chan;
> +	fsl_desc->n_tcds = sg_len;
> +	for (i = 0; i < sg_len; i++) {
> +		fsl_desc->tcd[i].vtcd = dma_pool_alloc(fsl_chan->tcd_pool,
> +					GFP_NOWAIT, &fsl_desc->tcd[i].ptcd);
> +		if (!fsl_desc->tcd[i].vtcd)
> +			goto free_on_err;
> +	}
> +	return fsl_desc;
> +
> +free_on_err:
> +	while (--i >= 0)
> +		dma_pool_free(fsl_chan->tcd_pool, fsl_desc->tcd[i].vtcd,
> +				fsl_desc->tcd[i].ptcd);
> +	kfree(fsl_desc);
> +	return NULL;
> +}
> +
> +static struct dma_async_tx_descriptor *fsl_edma_prep_dma_cyclic(
> +		struct dma_chan *chan, dma_addr_t dma_addr, size_t buf_len,
> +		size_t period_len, enum dma_transfer_direction direction,
> +		unsigned long flags, void *context)
> +{
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +	struct fsl_edma_desc *fsl_desc;
> +	dma_addr_t dma_buf_next;
> +	int sg_len, i;
> +	u32 src_addr, dst_addr, last_sg, nbytes;
> +	u16 soff, doff, iter;
> +
> +	if (!fsl_chan->fsc.dir == DMA_MEM_TO_DEV &&
> +			!fsl_chan->fsc.dir == DMA_DEV_TO_MEM)
> +		return NULL;
you are ignoring the direction arg. Also use is_slave_direction() helper
> +
> +	sg_len = buf_len / period_len;
> +	fsl_desc = fsl_edma_alloc_desc(fsl_chan, sg_len);
> +	if (!fsl_desc)
> +		return NULL;
> +	fsl_desc->iscyclic = true;
> +
> +	dma_buf_next = dma_addr;
> +	nbytes = fsl_chan->fsc.addr_width * fsl_chan->fsc.burst;
> +	iter = period_len / nbytes;
> +	for (i = 0; i < sg_len; i++) {
> +		if (dma_buf_next >= dma_addr + buf_len)
> +			dma_buf_next = dma_addr;
> +
> +		/* get next sg's physical address */
> +		last_sg = fsl_desc->tcd[(i + 1) % sg_len].ptcd;
> +
> +		if (fsl_chan->fsc.dir == DMA_MEM_TO_DEV) {
> +			src_addr = dma_buf_next;
> +			dst_addr = fsl_chan->fsc.dev_addr;
> +			soff = fsl_chan->fsc.addr_width;
> +			doff = 0;
> +		} else {
> +			src_addr = fsl_chan->fsc.dev_addr;
> +			dst_addr = dma_buf_next;
> +			soff = 0;
> +			doff = fsl_chan->fsc.addr_width;
> +		}
> +
> +		fill_tcd_params(fsl_desc->tcd[i].vtcd, src_addr, dst_addr,
> +				fsl_chan->fsc.attr, soff, nbytes, 0,
> +				iter, iter, doff, last_sg, true, false, true);
> +		dma_buf_next += period_len;
> +	}
> +
> +	return vchan_tx_prep(&fsl_chan->vchan, &fsl_desc->vdesc, flags);
> +}
> +
> +static struct dma_async_tx_descriptor *fsl_edma_prep_slave_sg(
> +		struct dma_chan *chan, struct scatterlist *sgl,
> +		unsigned int sg_len, enum dma_transfer_direction direction,
> +		unsigned long flags, void *context)
> +{
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +	struct fsl_edma_desc *fsl_desc;
> +	struct scatterlist *sg;
> +	u32 src_addr, dst_addr, last_sg, nbytes;
> +	u16 soff, doff, iter;
> +	int i;
> +
> +	if (!fsl_chan->fsc.dir == DMA_MEM_TO_DEV &&
> +			!fsl_chan->fsc.dir == DMA_DEV_TO_MEM)
> +		return NULL;
ditto

> +
> +	fsl_desc = fsl_edma_alloc_desc(fsl_chan, sg_len);
> +	if (!fsl_desc)
> +		return NULL;
> +	fsl_desc->iscyclic = false;
> +
> +	nbytes = fsl_chan->fsc.addr_width * fsl_chan->fsc.burst;
> +	for_each_sg(sgl, sg, sg_len, i) {
> +		/* get next sg's physical address */
> +		last_sg = fsl_desc->tcd[(i + 1) % sg_len].ptcd;
> +
> +		if (fsl_chan->fsc.dir == DMA_MEM_TO_DEV) {
> +			src_addr = sg_dma_address(sg);
> +			dst_addr = fsl_chan->fsc.dev_addr;
> +			soff = fsl_chan->fsc.addr_width;
> +			doff = 0;
> +		} else {
> +			src_addr = fsl_chan->fsc.dev_addr;
> +			dst_addr = sg_dma_address(sg);
> +			soff = 0;
> +			doff = fsl_chan->fsc.addr_width;
> +		}
> +
> +		iter = sg_dma_len(sg) / nbytes;
> +		if (i < sg_len - 1) {
> +			last_sg = fsl_desc->tcd[(i + 1)].ptcd;
> +			fill_tcd_params(fsl_desc->tcd[i].vtcd, src_addr,
> +				dst_addr, fsl_chan->fsc.attr, soff, nbytes, 0,
> +				iter, iter, doff, last_sg, false, false, true);
> +		} else {
> +			last_sg = 0;
> +			fill_tcd_params(fsl_desc->tcd[i].vtcd, src_addr,
> +				dst_addr, fsl_chan->fsc.attr, soff, nbytes, 0,
> +				iter, iter, doff, last_sg, true, true, false);
> +		}
> +	}
> +
> +	return vchan_tx_prep(&fsl_chan->vchan, &fsl_desc->vdesc, flags);
> +}
> +
> +static void fsl_edma_xfer_desc(struct fsl_edma_chan *fsl_chan)
> +{
> +	struct fsl_edma_hw_tcd *tcd;
> +	struct virt_dma_desc *vdesc;
> +
> +	vdesc = vchan_next_desc(&fsl_chan->vchan);
> +	if (!vdesc)
> +		return;
> +	fsl_chan->edesc = to_fsl_edma_desc(vdesc);
> +	tcd = fsl_chan->edesc->tcd[0].vtcd;
> +	fsl_edma_set_tcd_params(fsl_chan, tcd->saddr, tcd->daddr, tcd->attr,
> +			tcd->soff, tcd->nbytes, tcd->slast, tcd->citer,
> +			tcd->biter, tcd->doff, tcd->dlast_sga, tcd->csr);
> +	fsl_edma_enable_request(fsl_chan);
> +	fsl_chan->status = DMA_IN_PROGRESS;
> +}
> +
> +static irqreturn_t fsl_edma_irq_handler(int irq, void *dev_id)
> +{
> +	struct fsl_edma_engine *fsl_edma = dev_id;
> +	unsigned int intr, ch;
> +	void __iomem *base_addr;
> +	struct fsl_edma_chan *fsl_chan;
> +
> +	base_addr = fsl_edma->membase;
> +
> +	intr = readl(base_addr + EDMA_INTR);
> +	if (!intr)
> +		return IRQ_NONE;
> +
> +	for (ch = 0; ch < fsl_edma->n_chans; ch++) {
> +		if (intr & (0x1 << ch)) {
> +			writeb(EDMA_CINT_CINT(ch), base_addr + EDMA_CINT);
> +
> +			fsl_chan = &fsl_edma->chans[ch];
> +
> +			spin_lock(&fsl_chan->vchan.lock);
> +			if (!fsl_chan->edesc->iscyclic) {
> +				list_del(&fsl_chan->edesc->vdesc.node);
> +				vchan_cookie_complete(&fsl_chan->edesc->vdesc);
> +				fsl_chan->edesc = NULL;
> +				fsl_chan->status = DMA_SUCCESS;
> +			} else {
> +				vchan_cyclic_callback(&fsl_chan->edesc->vdesc);
> +			}
> +
> +			if (!fsl_chan->edesc)
> +				fsl_edma_xfer_desc(fsl_chan);
> +
> +			spin_unlock(&fsl_chan->vchan.lock);
> +		}
> +	}
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t fsl_edma_err_handler(int irq, void *dev_id)
> +{
> +	struct fsl_edma_engine *fsl_edma = dev_id;
> +	unsigned int err, ch;
> +
> +	err = readl(fsl_edma->membase + EDMA_ERR);
> +	if (!err)
> +		return IRQ_NONE;
> +
> +	for (ch = 0; ch < fsl_edma->n_chans; ch++) {
> +		if (err & (0x1 << ch)) {
> +			fsl_edma_disable_request(&fsl_edma->chans[ch]);
> +			writeb(EDMA_CERR_CERR(ch), fsl_edma->membase + EDMA_CERR);
> +			fsl_edma->chans[ch].status = DMA_ERROR;
> +		}
> +	}
> +	return IRQ_HANDLED;
> +}
> +
> +
> +static void fsl_edma_issue_pending(struct dma_chan *chan)
> +{
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&fsl_chan->vchan.lock, flags);
> +
> +	if (vchan_issue_pending(&fsl_chan->vchan) && !fsl_chan->edesc)
> +		fsl_edma_xfer_desc(fsl_chan);
> +
> +	spin_unlock_irqrestore(&fsl_chan->vchan.lock, flags);
> +}
> +
> +static bool fsl_edma_filter_fn(struct dma_chan *chan, void *fn_param)
> +{
> +	struct fsl_edma_filter_param *fparam = fn_param;
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +
> +	if (fsl_chan->edmamux->mux_id != fparam->mux_id)
> +		return false;
> +
> +	fsl_chan->slot_id = fparam->slot_id;
> +	chan->private = fn_param;
why do you need to use chan->private?
> +	return true;
> +}
> +
> +static struct dma_chan *fsl_edma_xlate(struct of_phandle_args *dma_spec,
> +		struct of_dma *ofdma)
> +{
> +	dma_cap_mask_t mask;
> +	struct fsl_edma_filter_param fparam;
> +
> +	if (dma_spec->args_count != 2)
> +		return NULL;
> +
> +	fparam.mux_id = dma_spec->args[0];
> +	fparam.slot_id = dma_spec->args[1];
> +
> +	dma_cap_zero(mask);
> +	dma_cap_set(DMA_SLAVE, mask);
> +	dma_cap_set(DMA_CYCLIC, mask);
> +	return dma_request_channel(mask, fsl_edma_filter_fn, (void *)&fparam);
> +}
> +
> +static int fsl_edma_alloc_chan_resources(struct dma_chan *chan)
> +{
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +	struct fsl_edma_filter_param *data = chan->private;
> +	unsigned char val;
> +
> +	val = EDMAMUX_CHCFG_ENBL | EDMAMUX_CHCFG_SOURCE(data->slot_id);
okay, so what does the slot_id mean?

> +	fsl_edmamux_config_chan(fsl_chan, val);
> +
> +	fsl_chan->tcd_pool = dma_pool_create("tcd_pool", chan->device->dev,
> +				sizeof(struct fsl_edma_hw_tcd),
> +				32, 0);
> +	return 0;
> +}
> +
> +static void fsl_edma_free_chan_resources(struct dma_chan *chan)
> +{
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +
> +	fsl_edma_disable_request(fsl_chan);
> +	fsl_edmamux_config_chan(fsl_chan, EDMAMUX_CHCFG_DIS);
> +	fsl_chan->edesc = NULL;
> +	vchan_free_chan_resources(&fsl_chan->vchan);
> +	dma_pool_destroy(fsl_chan->tcd_pool);
> +	fsl_chan->tcd_pool = NULL;
> +}
> +
> +static int
> +fsl_init_edmamux(struct platform_device *pdev, struct fsl_edma_engine *fsl_edma)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct fsl_edma_dmamux *fsl_edmamux;
> +	struct device_node *phandle;
> +	const void *prop;
> +	struct resource res;
> +	int len, n_muxes, chans_per_mux, ch_off;
> +	int i, j;
> +	int ret;
> +
> +	prop = of_get_property(np, "fsl,dma-mux", &len);
> +	if (!prop) {
> +		dev_err(&pdev->dev, "Can't get DMAMUX.\n");
> +		return -EINVAL;
> +	}
> +
> +	n_muxes = len / sizeof(u32);
> +	chans_per_mux = fsl_edma->n_chans / n_muxes;
> +	fsl_edmamux = devm_kzalloc(&pdev->dev,
> +			sizeof(struct fsl_edma_dmamux) * n_muxes, GFP_KERNEL);
> +	if (!fsl_edmamux)
> +		return -ENOMEM;
> +
> +	fsl_edma->n_muxes = 0;
> +	fsl_edma->edmamux = fsl_edmamux;
> +	for (i = 0; i < n_muxes; i++) {
> +		phandle = of_parse_phandle(np, "fsl,dma-mux", i);
> +		ret = of_address_to_resource(phandle, 0, &res);
> +		if (ret)
> +			return ret;
> +		fsl_edmamux->membase = devm_ioremap_resource(&pdev->dev, &res);
> +		if (IS_ERR(fsl_edmamux->membase))
> +			return PTR_ERR(fsl_edmamux->membase);
> +
> +		fsl_edmamux->clk = of_clk_get(phandle, 0);
> +		if (IS_ERR(fsl_edmamux->clk)) {
> +			dev_err(&pdev->dev, "Missing DMAMUX clock.\n");
> +			return PTR_ERR(fsl_edmamux->clk);
> +		}
> +
> +		ret = clk_prepare_enable(fsl_edmamux->clk);
> +		if (ret) {
> +			dev_err(&pdev->dev, "DMAMUX clk enable failed.\n");
> +			return ret;
> +		}
> +
> +		ret = of_property_read_u32_index(phandle, "fsl,dmamux-id", 0,
> +				&fsl_edmamux->mux_id);
> +		if (ret) {
> +			dev_err(&pdev->dev, "Can't get dmamux-id.\n");
> +			return ret;
> +		}
> +
> +		ch_off = fsl_edma->n_muxes * chans_per_mux;
> +		for (j = 0; j < chans_per_mux; j++)
> +			fsl_edma->chans[ch_off + j].edmamux = fsl_edmamux;
> +
> +		fsl_edmamux++;
> +		fsl_edma->n_muxes++;
> +	}
> +	return 0;
> +}
> +
> +static int
> +fsl_edma_init_irq(struct platform_device *pdev, struct fsl_edma_engine *fsl_edma)
> +{
> +	int ret;
> +
> +	fsl_edma->edmairq.txirq = platform_get_irq_byname(pdev, "edma-tx");
> +	if (fsl_edma->edmairq.txirq < 0) {
> +		dev_err(&pdev->dev, "Can't get edma-tx irq.\n");
> +		return fsl_edma->edmairq.txirq;
> +	}
> +
> +	ret = devm_request_irq(&pdev->dev, fsl_edma->edmairq.txirq,
> +			fsl_edma_irq_handler, IRQF_SHARED, "eDMA tx", fsl_edma);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Can't register eDMA tx IRQ.\n");
> +		return  ret;
> +	}
> +
> +	fsl_edma->edmairq.errirq = platform_get_irq_byname(pdev, "edma-err");
> +	if (fsl_edma->edmairq.errirq < 0) {
> +		dev_err(&pdev->dev, "Can't get edma-err irq.\n");
> +		return fsl_edma->edmairq.errirq;
> +	}
> +
> +	ret = devm_request_irq(&pdev->dev, fsl_edma->edmairq.errirq,
> +			fsl_edma_err_handler, IRQF_SHARED, "eDMA err", fsl_edma);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Can't register eDMA err IRQ.\n");
> +		return  ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int fsl_edma_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct fsl_edma_engine *fsl_edma;
> +	struct fsl_edma_chan *fsl_chan;
> +	struct resource *res;
> +	int len, chans;
> +	int ret, i;
> +
> +	ret = of_property_read_u32_index(np, "dma-channels", 0, &chans);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Can't get dma-channels.\n");
> +		return ret;
> +	}
> +
> +	len = sizeof(*fsl_edma) + sizeof(*fsl_chan) * chans;
> +	fsl_edma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> +	if (!fsl_edma)
> +		return -ENOMEM;
> +
> +	fsl_edma->n_chans = chans;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	fsl_edma->membase = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(fsl_edma->membase))
> +		return PTR_ERR(fsl_edma->membase);
> +
> +	ret = fsl_init_edmamux(pdev, fsl_edma);
> +	if (ret)
> +		return ret;
> +
> +	ret = fsl_edma_init_irq(pdev, fsl_edma);
> +	if (ret)
> +		return ret;
> +
> +	INIT_LIST_HEAD(&fsl_edma->dma_dev.channels);
> +	for (i = 0; i < fsl_edma->n_chans; i++) {
> +		struct fsl_edma_chan *fsl_chan = &fsl_edma->chans[i];
> +
> +		fsl_chan->edma = fsl_edma;
> +
> +		fsl_chan->vchan.desc_free = fsl_edma_free_desc;
> +		vchan_init(&fsl_chan->vchan, &fsl_edma->dma_dev);
> +
> +		writew(0x0, fsl_edma->membase + EDMA_TCD_CSR(i));
> +		fsl_edmamux_config_chan(fsl_chan, EDMAMUX_CHCFG_DIS);
> +	}
> +
> +	dma_cap_set(DMA_SLAVE, fsl_edma->dma_dev.cap_mask);
> +	dma_cap_set(DMA_CYCLIC, fsl_edma->dma_dev.cap_mask);
> +
> +	fsl_edma->dma_dev.dev = &pdev->dev;
> +	fsl_edma->dma_dev.device_alloc_chan_resources
> +		= fsl_edma_alloc_chan_resources;
> +	fsl_edma->dma_dev.device_free_chan_resources
> +		= fsl_edma_free_chan_resources;
> +	fsl_edma->dma_dev.device_tx_status = fsl_edma_tx_status;
> +	fsl_edma->dma_dev.device_prep_slave_sg = fsl_edma_prep_slave_sg;
> +	fsl_edma->dma_dev.device_prep_dma_cyclic = fsl_edma_prep_dma_cyclic;
> +	fsl_edma->dma_dev.device_control = fsl_edma_control;
> +	fsl_edma->dma_dev.device_issue_pending = fsl_edma_issue_pending;
> +
> +	platform_set_drvdata(pdev, fsl_edma);
> +
> +	ret = dma_async_device_register(&fsl_edma->dma_dev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Can't register Freescale eDMA engine.\n");
> +		return ret;
> +	}
> +
> +	ret = of_dma_controller_register(np, fsl_edma_xlate, fsl_edma);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Can't register Freescale eDMA of_dma.\n");
> +		dma_async_device_unregister(&fsl_edma->dma_dev);
> +		return ret;
> +	}
> +
> +	/* enable round robin arbitration */
> +	writel(EDMA_CR_ERGA | EDMA_CR_ERCA, fsl_edma->membase + EDMA_CR);
> +
> +	return 0;
> +}
> +
> +static int fsl_edma_remove(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct fsl_edma_engine *fsl_edma = platform_get_drvdata(pdev);
> +	int i;
> +
> +	of_dma_controller_free(np);
> +	dma_async_device_unregister(&fsl_edma->dma_dev);
> +
> +	for (i = 0; i < fsl_edma->n_muxes; i++) {
> +		clk_disable_unprepare(fsl_edma->edmamux[i].clk);
> +		clk_put(fsl_edma->edmamux[i].clk);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id fsl_edma_dt_ids[] = {
> +	{ .compatible = "fsl,vf610-edma", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, fsl_edma_dt_ids);
> +
> +static struct platform_driver fsl_edma_driver = {
> +	.driver		= {
> +		.name	= "fsl-edma",
> +		.owner  = THIS_MODULE,
> +		.of_match_table = fsl_edma_dt_ids,
> +	},
> +	.probe          = fsl_edma_probe,
> +	.remove		= fsl_edma_remove,
> +};
> +
> +module_platform_driver(fsl_edma_driver);
> +
> +MODULE_ALIAS("platform:fsl-edma");
> +MODULE_DESCRIPTION("Freescale eDMA engine driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.8.0
> 
> 

--