linux-kernel - Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver

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Date:   Wed, 26 Jul 2017 07:38:02 +0000
From:   Pierre Yves MORDRET <pierre-yves.mordret@...com>
To:     Vinod Koul <vinod.koul@...el.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" <dmaengine@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/5] dmaengine: Add STM32 DMAMUX driver



On 07/26/2017 07:29 AM, Vinod Koul wrote:
> On Mon, Jul 24, 2017 at 01:55:10PM +0000, Pierre Yves MORDRET wrote:
> 
>>>> +
>>>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>> +	if (!res)
>>>> +		return -ENODEV;
>>>> +
>>>> +	iomem = devm_ioremap_resource(&pdev->dev, res);
>>>> +	if (!iomem)
>>>> +		return -ENOMEM;
>>>> +
>>>> +	spin_lock_init(&stm32_dmamux->lock);
>>>> +
>>>> +	stm32_dmamux->clk = devm_clk_get(&pdev->dev, NULL);
>>>> +	if (IS_ERR(stm32_dmamux->clk)) {
>>>> +		dev_info(&pdev->dev, "Missing controller clock\n");
>>>
>>> Can you check for EPROBE_DEFER and print only for if that is not the error
>>> otherwise we end up sapmming with defered probe issues
>>>
>>
>> This is what you meant ?
>> 	if (IS_ERR(stm32_dmamux->clk) != EPROBE_DEFER) {
>> 		dev_info(&pdev->dev, "Missing controller clock\n");
>> 		return PTR_ERR(stm32_dmamux->clk);
>> 	}
>>
>> OR
>>
>> 	if (IS_ERR(stm32_dmamux->clk)) {
>> 		if (IS_ERR(stm32_dmamux->clk) != EPROBE_DEFER)
>> 			dev_info(&pdev->dev, "Missing controller clock\n");
>> 		return PTR_ERR(stm32_dmamux->clk);
>> 	}
> 
> This one please
> 

ok

>>
>>>> +
>>>> +#ifndef __DMA_STM32_DMAMUX_H
>>>> +#define __DMA_STM32_DMAMUX_H
>>>> +
>>>> +#if defined(CONFIG_STM32_DMAMUX)
>>>> +int stm32_dmamux_set_config(struct device *dev, void *route_data, u32 chan_id);
>>>
>>> Why do we need a custom API in this case?
>>>
>>
>> This API is called by DMA when a slave is requested by client. DMA can work
>> without DMAMUX this API has been put in place to configure DMAMUX whether client
>> is requesting a DMAMUX Channel instead of a DMA one.
> 
> You mean the dmaengine driver right?
> 

Yes. The API is mainly called by "device_config" through out STM32 DMA Driver
when a router is in place for client.
Please refer to Patch 4/5 on this set.

Thanks
Py