Re: [PATCH 1/3] i2c: add DMA support for freescale i2c driver

[Marek Vasut]

On Monday, March 03, 2014 at 11:23:33 AM, Yao Yuan wrote:
> Hi, Marek
> 
> Marek Vasut wrote:
> > On Thursday, February 27, 2014 at 07:05:14 AM, Yuan Yao wrote:
> > 
> > [...]
> > 
> > > +static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx) {
> > > +	struct imx_i2c_dma *dma = i2c_imx->dma;
> > > +	struct dma_chan *dma_chan;
> > > +
> > > +	dma_chan = dma->chan_tx;
> > > +	dma->chan_tx = NULL;
> > > +	dma->buf_tx = 0;
> > > +	dma->len_tx = 0;
> > > +	dma_release_channel(dma_chan);
> > > +
> > > +	dma_chan = dma->chan_rx;
> > > +	dma->chan_tx = NULL;
> > > +	dma->buf_rx = 0;
> > > +	dma->len_rx = 0;
> > > +	dma_release_channel(dma_chan);
> > 
> > You must make _DEAD_ _SURE_ this function is not ever called while the
> > DMA is still active. In your case, I have a feeling that's not handled.
> 
> Thanks for your attention.
> This few days I look up the code for the realization of
> dma_release_channel(). I found that it will disable the dma request first.
> So it's may safe. And drivers hadn't check whether dma is still active
> before dma_release_channel() as a usually usage. Because it will be
> disabled automatic.
> 
> The only problem is that, it will be forced to cancel the transfer which
> was not yet completed. Looking forward to hearing from you.

OK

Best regards,
Marek Vasut
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