linux-kernel - Re: [Patch v4 1/2] dmaengine: add Qualcomm BAM dma driver

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Message-ID: <20140204192426.GA16943@qualcomm.com>
Date:	Tue, 4 Feb 2014 13:24:26 -0600
From:	Andy Gross <agross@...eaurora.org>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [Patch v4 1/2] dmaengine: add Qualcomm BAM dma driver

On Tue, Feb 04, 2014 at 12:58:25PM +0100, Lars-Peter Clausen wrote:
> On 02/04/2014 12:04 AM, Andy Gross wrote:
> [...]
> >+static int bam_dma_remove(struct platform_device *pdev)
> >+{
> >+	struct bam_device *bdev = platform_get_drvdata(pdev);
> >+	u32 i;
> >+
> >+	dma_async_device_unregister(&bdev->common);
> >+	of_dma_controller_free(pdev->dev.of_node);
> 
> The controller should first be removed from the of lookup table,
> then free the device.
> 
Ah right, had this reversed.

> >+
> >+	/* mask all interrupts for this execution environment */
> >+	writel_relaxed(0, bdev->regs + BAM_IRQ_SRCS_MSK_EE(bdev->ee));
> 
> You still need to free the interrupt to make this race free,
> especially on a multi-processor system. free_irq() acts as a
> synchronization point that makes sure that interrupt handler has
> finished running and that no new interrupt handlers are being run
> after this point. Just masking the interrupt in the control register
> does not provide these guarantees.

ok i'll just add in a devm_free_irq().  The only good thing then about using the
devm_request_irq is the cleanup on error paths in the probe.

> >+
> >+	for (i = 0; i < bdev->num_channels; i++) {
> >+		bam_dma_terminate_all(&bdev->channels[i]);
> >+		tasklet_kill(&bdev->channels[i].vc.task);
> >+	}
> >+
> >+	tasklet_kill(&bdev->task);
> >+
> >+	clk_disable_unprepare(bdev->bamclk);
> >+
> >+	return 0;
> >+}
> [...]
> 

-- 
sent by an employee of the Qualcomm Innovation Center, Inc.
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