[PATCH v7 2/3] I2C: mediatek: Add driver for MediaTek I2C controller

Wolfram Sang wsa at the-dreams.de
Sun May 17 23:37:42 PDT 2015

> > > +		rpaddr = dma_map_single(i2c->adap.dev.parent, msgs->buf,
> > > +						msgs->len, DMA_FROM_DEVICE);
> > 
> > I think you shouldn't use the adapter device here and later, but the dma
> > channel device.
> > 
> In MTK SoC, each I2C controller has its own DMA, and this DMA can't be
> used by other hardware.
> So I tend to use DMA directly, not through DMA channel.
> Even so, "i2c->adap.dev.parent" is not suitable here. I will change to
> use i2c->dev here. (Reference i2c-at91.c).

The better reference would be i2c-sh_mobile.c, especially commit
8cfcae9f0595bf0d145a67cfaa1051804a301d7c ("i2c: sh_mobile: use proper
device for mapping DMA memory") ;) The request to use the DMA channel
device came from the DMA folks, so if there is no real reason for an
exception, please use the channel device.

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