From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vinod Koul <vinod.koul@intel.com>
Subject: Re: [PATCH v4 2/4] dmaengine: Add STM32 MDMA driver
Date: Thu, 28 Sep 2017 13:43:11 +0530
Message-ID: <20170928081310.GA30097@localhost>
References: <1503671466-32029-1-git-send-email-pierre-yves.mordret@st.com>
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Sender: linux-kernel-owner@vger.kernel.org
To: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Cc: Rob Herring <robh+dt@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Maxime Coquelin <mcoquelin.stm32@gmail.com>, Alexandre Torgue <alexandre.torgue@st.com>, Russell King <linux@armlinux.org.uk>, Dan Williams <dan.j.williams@intel.com>, M'boumba Cedric Madianga <cedric.madianga@gmail.com>, Fabrice GASNIER <fabrice.gasnier@st.com>, Herbert Xu <herbert@gondor.apana.org.au>, Fabien DESSENNE <fabien.dessenne@st.com>, Amelie Delaunay <amelie.delaunay@st.com>, dmaengine@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
List-Id: devicetree@vger.kernel.org

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