On Tuesday 09 August 2016 05:03 PM, Mark Brown wrote:
> On Tue, Aug 09, 2016 at 04:33:11PM +0530, Vignesh R wrote:
>
>> +static int ti_qspi_map_buf(struct ti_qspi *qspi, void *buf,
>> + unsigned int len, struct sg_table *sgt)
>> +{
>> + unsigned int max_seg_size =
>> + dma_get_max_seg_size(qspi->rx_chan->device->dev);
>> + unsigned int desc_len = min_t(int, max_seg_size, PAGE_SIZE);
>> + int sgs = DIV_ROUND_UP(len + offset_in_page(buf), desc_len);
>> + struct page *vm_page;
>> + size_t min;
>> + int i, ret;
>> +
>> + ret = sg_alloc_table(sgt, sgs, GFP_KERNEL);
>> + if (ret)
>> + return ret;
>> +
>> + for (i = 0; i < sgs; i++) {
>> + min = min_t(size_t, len, desc_len -
>> + offset_in_page(buf));
>> + vm_page = kmap_to_page(buf);
>> + if (!vm_page) {
>> + sg_free_table(sgt);
>> + return -ENOMEM;
>> + }
>> + sg_set_page(&sgt->sgl[i], vm_page, min,
>> + offset_in_page(buf));
>> + buf += min;
>> + len -= min;
>
> This looks a lot like the core code for mapping the buffers - why is
> this open coded rather than reused?
According to this thread[1], converting virtual address
pointer into scatterlist which is then DMA mapped is unsafe on systems
with certain cache architecture. Hence, I added code to handle kmap
buffers inside the driver rather than updating generic spi-core code.
If its okay to update the spi_map_buf() to handle kmap buffers as above
then I can submit the patch accordingly.
[1]https://patchwork.kernel.org/patch/8712161/
--
Regards
Vignesh
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