RE: [PATCH V9 3/5] i2c: tegra: Add DMA support

[Sowjanya Komatineni]

>	rx_chan = dma_request_slave_channel_reason(i2c_dev->dev, "rx");
>	if (IS_ERR(rx_chan))
>		return PTR_ERR(rx_chan);
>
>
> > +
> > +	dma_chan = dma_request_slave_channel_reason(i2c_dev->dev, "tx");
> > +	if (IS_ERR(dma_chan)) {
> > +		err = PTR_ERR(dma_chan);
> > +		goto error;
>
> It's a good practice to release resources in opposite order to the allocation. Hence better to write this as:
>
>		goto err_release_rx;
>
> > +	}
> > +
> > +	i2c_dev->tx_dma_chan = dma_chan;
> > +
> > +	dma_buf = dma_alloc_coherent(i2c_dev->dev,
> > +				     i2c_dev->dma_buf_size, &dma_phys,
> > +				     GFP_KERNEL | __GFP_NOWARN);
> > +
> > +	if (!dma_buf) {
> > +		dev_err(i2c_dev->dev, "failed to allocate the DMA buffer\n");
> > +		err = -ENOMEM;
> > +		goto error;
>
>		goto err_release_tx;
>
> > +	}
> > +
> > +	i2c_dev->dma_buf = dma_buf;
> > +	i2c_dev->dma_phys = dma_phys;	i2c_dev->rx_dma_chan = rx_chan;
>	i2c_dev->tx_dma_chan = tx_chan;
>
> > +	return 0;
> > +
> > +error:
> > +	if (i2c_dev->tx_dma_chan)
> > +		dma_release_channel(i2c_dev->tx_dma_chan);
> > +
> > +	if (i2c_dev->rx_dma_chan)
> > +		dma_release_channel(i2c_dev->rx_dma_chan);
>
> error_release_tx:
>	dma_release_channel(tx_chan);
> error_release_rx:
>	dma_release_channel(rx_chan);
>
> > +
> > +	return err;

I am releasing resources in reverse order to allocation.
Trying for rx allocation followed by tx allocation
During release releasing tx and then rx.
In case if tx allocation fails, doesnât go thru release. If rx or buf allocation fails, releases tx first and then rx