linux-kernel - Re: [PATCH V2 2/2] dmaengine: tegra-adma: Add support for Tegra210 ADMA

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Date:	Wed, 14 Oct 2015 16:57:59 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	Laxman Dewangan <ldewangan@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Arnd Bergmann <arnd@...db.de>, dmaengine@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/2] dmaengine: tegra-adma: Add support for Tegra210
 ADMA

On Mon, Oct 05, 2015 at 01:10:07PM +0100, Jon Hunter wrote:

> +static enum dma_status tegra_adma_tx_status(struct dma_chan *dc,
> +					    dma_cookie_t cookie,
> +					    struct dma_tx_state *txstate)
> +{
> +	struct tegra_adma_chan *tdc = to_tegra_adma_chan(dc);
> +	struct tegra_adma_desc *desc;
> +	struct virt_dma_desc *vd;
> +	enum dma_status ret;
> +	unsigned long flags;
> +	unsigned int residual;
> +
> +	spin_lock_irqsave(&tdc->lock, flags);
> +
> +	ret = dma_cookie_status(dc, cookie, txstate);
> +	if (ret == DMA_COMPLETE) {
> +		spin_unlock_irqrestore(&tdc->lock, flags);
> +		return ret;
> +	}

txstate can be NULL, upon which below code doesn't help in getting executed
so bailing here or above case is fine

> +static struct dma_async_tx_descriptor *tegra_adma_prep_dma_cyclic(
> +	struct dma_chan *dc, dma_addr_t buf_addr, size_t buf_len,
> +	size_t period_len, enum dma_transfer_direction direction,
> +	unsigned long flags)
> +{
> +	struct tegra_adma_chan *tdc = to_tegra_adma_chan(dc);
> +	struct tegra_adma_desc *desc = NULL;
> +
> +	if (!tdc->config_valid) {
> +		dev_err(tdc2dev(tdc), "ADMA slave configuration not set\n");
> +		return NULL;
> +	}
> +
> +	if (!buf_len || !period_len || period_len > ADMA_CH_TC_COUNT_MASK) {
> +		dev_err(tdc2dev(tdc), "invalid buffer/period len\n");
> +		return NULL;
> +	}
> +
> +	if (buf_len % period_len) {
> +		dev_err(tdc2dev(tdc), "buf_len not a multiple of period_len\n");
> +		return NULL;
> +	}
> +
> +	if (!IS_ALIGNED(buf_addr, 4)) {
> +		dev_err(tdc2dev(tdc), "invalid buffer alignment\n");
> +		return NULL;
> +	}
> +
> +	desc = kzalloc(sizeof(*desc), GFP_ATOMIC);

we recommend GFP_NOWAIT for the subsystem

> +static int tegra_adma_remove(struct platform_device *pdev)
> +{
> +	struct tegra_adma *tdma = platform_get_drvdata(pdev);
> +	struct tegra_adma_chan *tdc;
> +	int i;
> +
> +	dma_async_device_unregister(&tdma->dma_dev);
> +
> +	for (i = 0; i < tdma->nr_channels; ++i) {
> +		tdc = &tdma->channels[i];
> +		tasklet_kill(&tdc->vc.task);
> +	}
this is good, but your irq is still active and can fire and thus trigger
more tasklets!

-- 
~Vinod
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