[PATCH 1/3] spi/qspi: Add memory mapped read support.

Sourav Poddar sourav.poddar at ti.com
Thu Oct 17 21:06:06 PDT 2013

On Friday 18 October 2013 05:12 AM, Mark Brown wrote:
> On Thu, Oct 17, 2013 at 01:03:26PM +0000, Gupta, Pekon wrote:
>> mtd_read() {
>> 	if (flash->mmap_mode)
>> 		if (dma_available)
>> 			read_via_dma(destination, source, length);
>> 		else
>> 			memcpy(destination, source, length);
>> 	else
>> 		/* use spi frame-work by default */
>> }
>> Are you looking for comparison between  read_via_dma() v/s memcpy() ?
> No, I'm looking for a comparison of normal SPI mode (which I'd have
> expected to DMA) and the memcpy() mode.
>> If yes, then unfortunately we are bit constrained because our controller
>> does not support DMA. So, we have to depend on CPU based memcpy()
>> only. However, use of DMA can be added as an independent patch on
>> top of this CASE-2 patch.
> However if the controller can't DMA at all then that's not going to be
> possible...  am I understanding you correctly that normal SPI can't DMA?
Yes, you are correct, the normal SPI cant DMA.

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