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Message-ID: <20130805165755.GD13091@e106331-lin.cambridge.arm.com>
Date: Mon, 5 Aug 2013 17:57:55 +0100
From: Mark Rutland <mark.rutland@....com>
To: Jonas Jensen <jonas.jensen@...il.com>
Cc: "linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"arm@...nel.org" <arm@...nel.org>,
"vinod.koul@...el.com" <vinod.koul@...el.com>,
"djbw@...com" <djbw@...com>, "arnd@...db.de" <arnd@...db.de>,
"linux@....linux.org.uk" <linux@....linux.org.uk>
Subject: Re: [PATCH v7] dmaengine: Add MOXA ART DMA engine driver
On Mon, Aug 05, 2013 at 03:37:37PM +0100, Jonas Jensen wrote:
> The MOXA ART SoC has a DMA controller capable of offloading expensive
> memory operations, such as large copies. This patch adds support for
> the controller including four channels. Two of these are used to
> handle MMC copy on the UC-7112-LX hardware. The remaining two can be
> used in a future audio driver or client application.
>
> Signed-off-by: Jonas Jensen <jonas.jensen@...il.com>
> ---
>
> Notes:
> Thanks for the replies.
>
> Changes since v6:
>
> 1. move callback from interrupt context to tasklet
> 2. remove callback and callback_param, use those provided by tx_desc
> 3. don't rely on structs for register offsets
> 4. remove local bool "found" variable from moxart_alloc_chan_resources()
> 5. check return value of irq_of_parse_and_map
> 6. use devm_request_irq instead of setup_irq
> 7. elaborate commit message
>
> device tree bindings document:
> 8. in the example, change "#dma-cells" to "<2>"
>
> Applies to next-20130805
>
> .../devicetree/bindings/dma/moxa,moxart-dma.txt | 21 +
> drivers/dma/Kconfig | 7 +
> drivers/dma/Makefile | 1 +
> drivers/dma/moxart-dma.c | 614 +++++++++++++++++++++
> 4 files changed, 643 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/dma/moxa,moxart-dma.txt
> create mode 100644 drivers/dma/moxart-dma.c
>
> diff --git a/Documentation/devicetree/bindings/dma/moxa,moxart-dma.txt b/Documentation/devicetree/bindings/dma/moxa,moxart-dma.txt
> new file mode 100644
> index 0000000..5b9f82c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/moxa,moxart-dma.txt
> @@ -0,0 +1,21 @@
> +MOXA ART DMA Controller
> +
> +See dma.txt first
> +
> +Required properties:
> +
> +- compatible : Must be "moxa,moxart-dma"
> +- reg : Should contain registers location and length
> +- interrupts : Should contain the interrupt number
> +- #dma-cells : Should be 2
> + cell index 0: channel number between 0-3
> + cell index 1: line request number
> +
> +Example:
> +
> + dma: dma@...00000 {
> + compatible = "moxa,moxart-dma";
> + reg = <0x90500000 0x1000>;
> + interrupts = <24 0>;
> + #dma-cells = <2>;
> + };
Thanks for the updates on this. :)
The binding and example look sensible to me; it would be nice if someone
familiar with the dma subsystem could check that this has the necessary
information.
[...]
> +static int moxart_alloc_chan_resources(struct dma_chan *chan)
> +{
> + struct moxart_dma_chan *mchan = to_moxart_dma_chan(chan);
> + int i;
> +
> + for (i = 0; i < APB_DMA_MAX_CHANNEL; i++) {
> + if (i == mchan->ch_num
> + && !mchan->allocated) {
> + dev_dbg(chan2dev(chan), "%s: allocating channel #%d\n",
> + __func__, mchan->ch_num);
> + mchan->allocated = true;
> + return 0;
> + }
> + }
Come to think of it, why do you need to iterate over all of the channels
to handle a particular channel number that you already know, and already
have the struct for?
I'm not familiar with the dma subsystem, and I couldn't spot when the
dma channel is actually assigned/selected prior to this.
[...]
> +static enum dma_status moxart_tx_status(struct dma_chan *chan,
> + dma_cookie_t cookie,
> + struct dma_tx_state *txstate)
> +{
> + enum dma_status ret;
> +
> + ret = dma_cookie_status(chan, cookie, txstate);
> + if (ret == DMA_SUCCESS || !txstate)
> + return ret;
> +
> + return ret;
No special status handling?
This function is equivalent to:
return dma_cookie_status(chan, cookie, txstate);
[...]
> +static int moxart_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct device_node *node = dev->of_node;
> + struct resource *res;
> + static void __iomem *dma_base_addr;
> + int ret, i;
> + unsigned int irq;
> + struct moxart_dma_chan *mchan;
> + struct moxart_dma_container *mdc;
> +
> + mdc = devm_kzalloc(dev, sizeof(*mdc), GFP_KERNEL);
> + if (!mdc) {
> + dev_err(dev, "can't allocate DMA container\n");
> + return -ENOMEM;
> + }
> +
> + irq = irq_of_parse_and_map(node, 0);
> + if (irq <= 0) {
> + dev_err(dev, "irq_of_parse_and_map failed\n");
> + return -EINVAL;
> + }
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + dma_base_addr = devm_ioremap_resource(dev, res);
> + if (IS_ERR(dma_base_addr)) {
> + dev_err(dev, "devm_ioremap_resource failed\n");
> + return PTR_ERR(dma_base_addr);
> + }
> +
> + mdc->ctlr = pdev->id;
> + spin_lock_init(&mdc->dma_lock);
> +
> + dma_cap_zero(mdc->dma_slave.cap_mask);
> + dma_cap_set(DMA_SLAVE, mdc->dma_slave.cap_mask);
> +
> + moxart_dma_init(&mdc->dma_slave, dev);
> +
> + mchan = &mdc->slave_chans[0];
> + for (i = 0; i < APB_DMA_MAX_CHANNEL; i++, mchan++) {
> + mchan->ch_num = i;
> + mchan->base = dma_base_addr + 0x80 + i * REG_CHAN_SIZE;
> + mchan->allocated = 0;
> +
> + dma_cookie_init(&mchan->chan);
> + mchan->chan.device = &mdc->dma_slave;
> + list_add_tail(&mchan->chan.device_node,
> + &mdc->dma_slave.channels);
> +
> + dev_dbg(dev, "%s: mchans[%d]: mchan->ch_num=%d mchan->base=%p\n",
> + __func__, i, mchan->ch_num, mchan->base);
> + }
> +
> + ret = dma_async_device_register(&mdc->dma_slave);
What if this fails?
> + platform_set_drvdata(pdev, mdc);
> +
> + of_dma_controller_register(node, moxart_of_xlate, &moxart_dma_info);
> +
> + tasklet_init(&mdc->tasklet, moxart_dma_tasklet, (unsigned long)mdc);
> +
> + devm_request_irq(dev, irq, moxart_dma_interrupt, 0,
> + "moxart-dma-engine", mdc);
The return value of devm_request_irq should be checked; it might fail.
> +
> + dev_dbg(dev, "%s: IRQ=%d\n", __func__, irq);
> +
> + return ret;
> +}
Thanks,
Mark.
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