linux-kernel - Re: [PATCH v4 2/4] dmaengine: Add STM32 MDMA driver

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Date:   Thu, 28 Sep 2017 13:43:11 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Pierre-Yves MORDRET <pierre-yves.mordret@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Russell King <linux@...linux.org.uk>,
        Dan Williams <dan.j.williams@...el.com>,
        M'boumba Cedric Madianga <cedric.madianga@...il.com>,
        Fabrice GASNIER <fabrice.gasnier@...com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Fabien DESSENNE <fabien.dessenne@...com>,
        Amelie Delaunay <amelie.delaunay@...com>,
        dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/4] dmaengine: Add STM32 MDMA driver

On Fri, Aug 25, 2017 at 04:31:04PM +0200, Pierre-Yves MORDRET wrote:
> +static int stm32_mdma_probe(struct platform_device *pdev)
> +{

[snip]

> +	dmadev = devm_kzalloc(&pdev->dev, sizeof(*dmadev) + sizeof(u32) * count,
> +			      GFP_KERNEL);
> +	if (!dmadev)
> +		return -ENOMEM;
> +
> +	dmadev->nr_channels = nr_channels;
> +	dmadev->nr_requests = nr_requests;
> +	device_property_read_u32_array(&pdev->dev, "st,ahb-addr-masks",
> +				       dmadev->ahb_addr_masks,
> +				       count);
> +	dmadev->nr_ahb_addr_masks = count;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	dmadev->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(dmadev->base))
> +		return PTR_ERR(dmadev->base);
> +
> +	dmadev->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(dmadev->clk)) {
> +		dev_err(&pdev->dev, "Error: Missing controller clock\n");
> +		return PTR_ERR(dmadev->clk);
> +	}

I am assuming if clk is not availble at this point of time you return clk
error which maybe defer probe, right?

> +static struct platform_driver stm32_mdma_driver = {
> +	.driver = {
> +		.name = "stm32-mdma",
> +		.of_match_table = stm32_mdma_of_match,
> +	},
> +};
> +
> +static int __init stm32_mdma_init(void)
> +{
> +	return platform_driver_probe(&stm32_mdma_driver, stm32_mdma_probe);

and you register platform_driver_probe() which per
drivers/base/platform.c:760 is incompatible with defer probing.
So this need a fix

-- 
~Vinod