Re: [PATCH v6 3/3] dma: Add Freescale eDMA engine driver support

Mark Rutland
2013-11-14T10:46:57Z

On Wed, Sep 18, 2013 at 10:57:59AM +0100, 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.
>
> Signed-off-by: Alison Wang <b18965@freescale.com>
> Signed-off-by: Jingchang Lu <b35083@freescale.com>
> ---
> changes in v6:
> holding lock in dma_control to prevent race.
>
> changes in v5:
> config slave_id when dmaengine_slave_config intead of channel request.
> adding residue calculation and dma pause/resume device control.
>
> 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 | 944 +++++++++++++++++++++
> 4 files changed, 1039 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..60a8cb2
> --- /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

- interrupts: A list of interrupt-specifiers, one for each entry in
interrupt-names.

> +- 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:

No compatible?

Where are DMAMUX nodes expected to live?

How to they relate to the eDMA controller in HW? Are they a
subcomponent, or a logically separate unit that happens to be connected?

> +- 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

_which_ clock names do you expect? From the looks of the example, you
expect "dmamux".

>From the view of the DMAMUX, what is its clock input called? "dmamux"
doesn't look like what I'd expect for a clock name, but if the
documentation for the eDMA doesn't provide a name for it, "dmamux" is
fine.

If you're not using clock-names, it's useless. You _must_ define the set
of names you expect or it's unusable. If you do define a set of names,
then you should request clocks by name in the driver.

> +
> +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: dma-controller@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@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.

Nit: the phandle isn't part of the specifier. The cells after the
phandle are the specifier associated with the phandle.

[...]

> +static bool fsl_edma_filter_fn(struct dma_chan *chan, void *mux_id)
> +{
> + struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +
> + if (fsl_chan->edmamux->mux_id != (u32)mux_id)
> + return false;
> +
> + return true;

Why not:

return fsl_chan->edmamux->mux_id == (u32)mux_id;

[...]

> +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;

That's confusing, a node is not a phandle. Why not mux_np?

> + 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);

It would be nicer if we had a variant of of_count_phandle_with_args that
cound handle a fixed count of 0 args for this sort of thing.

> + 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);
> + }

Please acquire the clock by name:

fsl_edmamux->clk = of_clk_get_byname(phandle, "dmamux");

> +
> + 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);

Why not just of_property_read_u32?

> + 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_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);

Use of_property_read_u32.

Thanks,
Mark.