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

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Date:	Tue, 13 Oct 2015 13:50:11 +0200
From:	"M'boumba Cedric Madianga" <cedric.madianga@...il.com>
To:	Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc:	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, Kumar Gala <galak@...eaurora.org>,
	linux@....linux.org.uk, vinod.koul@...el.com,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org
Subject: Re: [PATCH 2/4] dmaengine: Add STM32 DMA driver

 Hi Maxime,

2015-10-13 13:25 GMT+02:00 M'boumba Cedric Madianga <cedric.madianga@...il.com>:

>>> +static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
>>> +                                   enum dma_transfer_direction direction,
>>> +                                   enum dma_slave_buswidth *buswidth)
>>> +{
>>> +       enum dma_slave_buswidth src_addr_width, dst_addr_width;
>>> +       u32 src_bus_width, dst_bus_width, src_burst_size, dst_burst_size;
>>> +       u32 src_maxburst, dst_maxburst;
>>> +       dma_addr_t src_addr, dst_addr;
>>> +
>>> +       src_addr_width = chan->dma_sconfig.src_addr_width;
>>> +       dst_addr_width = chan->dma_sconfig.dst_addr_width;
>>> +       src_maxburst = chan->dma_sconfig.src_maxburst;
>>> +       dst_maxburst = chan->dma_sconfig.dst_maxburst;
>>> +       src_addr = chan->dma_sconfig.src_addr;
>>> +       dst_addr = chan->dma_sconfig.dst_addr;
>>> +
>>> +       switch (direction) {
>>> +       case DMA_MEM_TO_DEV:
>>> +               dst_bus_width = stm32_get_dma_width(chan, dst_addr_width);
>>> +               if (dst_bus_width < 0)
>>> +                       return -EINVAL;
>>
>> dst_bus_width is a u32, so cannot be negative.
>> Also, you should propagate de error returned by stm32_get_dma_width().

> Good point. Thanks.
> I am going to replace u32 by int in the v2.
> It will be done in v2.
>
Finally, I prefer to return a default value from stm32_get_dma_width()
and stm32_get_dma_burst().
In that way, I will always be able to configure DMA transfer parameters.

BR,
Cedric
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