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Date: Thu, 17 Oct 2013 22:56:53 -0700
Message-ID: <CA+7tXihUBXK61cRDmn3tnY9FM7FUSZrhPpLry2VAfvwWJpJ6gQ@mail.gmail.com>
Subject: Re: [PATCH 1/3] spi/qspi: Add memory mapped read support.
From: Trent Piepho <tpiepho@gmail.com>
To: Sourav Poddar <sourav.poddar@ti.com>
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Cc: Peter Korsgaard <peter@korsgaard.com>, "Balbi, Felipe" <balbi@ti.com>,
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 Pekon" <pekon@ti.com>, "spi-devel-general@lists.sourceforge.net"
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On Thu, Oct 17, 2013 at 9:06 PM, Sourav Poddar <sourav.poddar@ti.com> wrote:
> On Friday 18 October 2013 05:12 AM, Mark Brown wrote:
>>> 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.

Hardware limitation or driver limitation?  Adding DMA support to the
driver might be much more useful than adding memory mapped read
support.