[U-Boot] [PATCH] DaVinci: Improve DaVinci SPI speed.

[Nick Thompson <nick.thompson@ge.com>]

On 17/06/10 16:10, Paulraj, Sandeep wrote:
> 
> 
>>
>> On 01/06/10 12:36, Delio Brignoli wrote:
>>> I have updated this patch based on the comments [1] by Wolfgang Denk and
>>> removed unused variables.
>>> [1][http://lists.denx.de/pipermail/u-boot/2010-May/071728.html]
>>>
>>> Reduce the number of reads per byte transferred on the BUF register from
>> 2 to 1 and
>>> take advantage of the TX buffer in the SPI module. On LogicPD OMAP-L138
>> EVM,
>>> SPI read throughput goes up from ~0.8Mbyte/s to ~1.3Mbyte/s. Tested with
>> a 2Mbyte image file.
>>> Remove unused variables in the spi_xfer() function.
>>>
>>> Signed-off-by: Delio Brignoli <dbrignoli@audioscience.com>
>>> Tested-by: Ben Gardiner <bengardiner@nanometrics.ca>
>>
>> Sorry, I'm a bit late to the party on this.
> 
> It is late. Pull request already sent to Wolfgang
>>
>> I have an alternative patch that tries to be even quicker, but I
>> don't have the same platform as Delio, so can't compare like with
>> like.
> 
> Compare it on your platform. I believe you have the OMAP L137.
> And post the results.

I don't have a scope to get an accurate measure. The best I can do
right now is use a serial snooper to time between me pressing return
and the next prompt turning up.

To try and drown out inaccuracies and delays, I ran:

	sf read 0xc0008000 0 0x800000

So 8MiB in a reasonably consistent 5.62 - 5.63 seconds, which is about
1.49MiB/s by my reckoning. A bit faster, but way short of 6.25MiB/s.

Nick.