[ PATCH V2 4/7] MTD : add the common code for GPMI controller driver

[Russell King - ARM Linux]

On Fri, Mar 25, 2011 at 06:22:58PM +0800, Huang Shijie wrote:
> +/* Can we use the upper's buffer directly for DMA? */
> +void prepare_data_dma(struct gpmi_nfc_data *this, enum dma_data_direction dr)
> +{
> +	struct mil *mil = &this->mil;
> +	struct scatterlist *sgl = &mil->data_sgl;
> +	int ret;
> +
> +	mil->direct_dma_map_ok = true;
> +
> +	/* first try to map the upper buffer directly */
> +	sg_init_one(sgl, mil->upper_buf, mil->upper_len);
> +	ret = dma_map_sg(this->dev, sgl, 1, dr);
> +	if (ret == 0) {
> +		/* We have to use our own DMA buffer. */
> +		sg_init_one(sgl, mil->data_buffer_dma, PAGE_SIZE);
> +		ret = dma_map_sg(this->dev, sgl, 1, dr);
> +		BUG_ON(ret == 0);
> +
> +		if (dr == DMA_TO_DEVICE)
> +			memcpy(mil->data_buffer_dma, mil->upper_buf,
> +				mil->upper_len);

Buggy.  Ensure data is present in the buffers _before_ mapping.

> +	case DMA_FOR_READ_DATA:
> +		if (mil->direct_dma_map_ok == false)
> +			memcpy(mil->upper_buf, (char *)mil->data_buffer_dma,
> +				mil->upper_len);
> +		dma_unmap_sg(this->dev, &mil->data_sgl, 1, DMA_FROM_DEVICE);

Buggy.  Only read data from buffers _after_ unmapping.