linux-kernel - Re: [PATCH 2/2] dmaengine: milbeaut-hdmac: Add HDMAC driver for Milbeaut platforms

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Date:   Mon, 24 Jun 2019 12:14:42 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     jassisinghbrar@...il.com
Cc:     dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org,
        mark.rutland@....com, orito.takao@...ionext.com,
        masami.hiramatsu@...aro.org, kasai.kazuhiro@...ionext.com,
        Jassi Brar <jaswinder.singh@...aro.org>
Subject: Re: [PATCH 2/2] dmaengine: milbeaut-hdmac: Add HDMAC driver for
 Milbeaut platforms

On 12-06-19, 19:52, jassisinghbrar@...il.com wrote:

> +#include <linux/bits.h>
> +#include <linux/clk.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/dmaengine.h>
> +#include <linux/interrupt.h>
> +#include <linux/iopoll.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_dma.h>

Do we need both, IIRC of_dma.h does include of.h!

> +/* mc->vc.lock must be held by caller */
> +static void milbeaut_chan_start(struct milbeaut_hdmac_chan *mc,
> +				struct milbeaut_hdmac_desc *md)
> +{
> +	struct scatterlist *sg;
> +	u32  cb, ca, src_addr, dest_addr, len;
           ^^
double space

> +static irqreturn_t milbeaut_hdmac_interrupt(int irq, void *dev_id)
> +{
> +	struct milbeaut_hdmac_chan *mc = dev_id;
> +	struct milbeaut_hdmac_desc *md;
> +	irqreturn_t ret = IRQ_HANDLED;
> +	u32 val;
> +
> +	spin_lock(&mc->vc.lock);
> +
> +	/* Ack and Disable irqs */
> +	val = readl_relaxed(mc->reg_ch_base + MLB_HDMAC_DMACB);
> +	val &= ~(FIELD_PREP(MLB_HDMAC_SS, 0x7));
                                         ^^^^
Magic ..?

> +static int milbeaut_hdmac_chan_pause(struct dma_chan *chan)
> +{
> +	struct virt_dma_chan *vc = to_virt_chan(chan);
> +	struct milbeaut_hdmac_chan *mc = to_milbeaut_hdmac_chan(vc);
> +	u32 val;
> +
> +	spin_lock(&mc->vc.lock);
> +	val = readl_relaxed(mc->reg_ch_base + MLB_HDMAC_DMACA);
> +	val |= MLB_HDMAC_PB;
> +	writel_relaxed(val, mc->reg_ch_base + MLB_HDMAC_DMACA);

We really should have an updatel() and friends in kernel, feel free to
add in your driver though!

> +static int milbeaut_hdmac_chan_init(struct platform_device *pdev,
> +				    struct milbeaut_hdmac_device *mdev,
> +				    int chan_id)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct milbeaut_hdmac_chan *mc = &mdev->channels[chan_id];
> +	char *irq_name;
> +	int irq, ret;
> +
> +	irq = platform_get_irq(pdev, chan_id);
> +	if (irq < 0) {
> +		dev_err(&pdev->dev, "failed to get IRQ number for ch%d\n",
> +			chan_id);
> +		return irq;
> +	}
> +
> +	irq_name = devm_kasprintf(dev, GFP_KERNEL, "milbeaut-hdmac-%d",
> +				  chan_id);
> +	if (!irq_name)
> +		return -ENOMEM;
> +
> +	ret = devm_request_irq(dev, irq, milbeaut_hdmac_interrupt,
> +			       IRQF_SHARED, irq_name, mc);

I tend to dislike using devm_request_irq(), we have no control over when
the irq is freed and what is a spirious irq is running while we are
unrolling, so IMHO it make sense to free up and ensure all tasklets are
quiesced when remove returns

> +	if (ret)
> +		return ret;
> +
> +	mc->mdev = mdev;
> +	mc->reg_ch_base = mdev->reg_base + MLB_HDMAC_CH_STRIDE * (chan_id + 1);
> +	mc->vc.desc_free = milbeaut_hdmac_desc_free;
> +	vchan_init(&mc->vc, &mdev->ddev);

who kills the vc->task?

> +static int milbeaut_hdmac_remove(struct platform_device *pdev)
> +{
> +	struct milbeaut_hdmac_device *mdev = platform_get_drvdata(pdev);
> +	struct dma_chan *chan;
> +	int ret;
> +
> +	/*
> +	 * Before reaching here, almost all descriptors have been freed by the
> +	 * ->device_free_chan_resources() hook. However, each channel might
> +	 * be still holding one descriptor that was on-flight at that moment.
> +	 * Terminate it to make sure this hardware is no longer running. Then,
> +	 * free the channel resources once again to avoid memory leak.
> +	 */
> +	list_for_each_entry(chan, &mdev->ddev.channels, device_node) {
> +		ret = dmaengine_terminate_sync(chan);
> +		if (ret)
> +			return ret;
> +		milbeaut_hdmac_free_chan_resources(chan);
> +	}
> +
> +	of_dma_controller_free(pdev->dev.of_node);
> +	dma_async_device_unregister(&mdev->ddev);
> +	clk_disable_unprepare(mdev->clk);

And as suspected we have active tasklets and irq at this time :(
-- 
~Vinod