[U-Boot] [PATCH RFC] NAND: Improve read performance from Large Page NAND devices

[Josh Gelinske]

What kind of CPU usage are you seeing? I am throughput of ~1.9MBs for writes
on a Samsung K9WBG08U1M 4GB with 4K page but with high cpu usage.



Nick Thompson-9 wrote:
> 
> On 09/12/09 11:02, Wolfgang Denk wrote:
>> Dear Nick Thompson,
>> 
>> In message <4B1E71D9.6080802 at ge.com> you wrote:
>>> Improve read performance from Large Page NAND devices.
>>>
>>> This patch produces a ~31% improvement in oob_first read speed (on a
>>> 300MHz ARM9). The time for a mid-buffer 2k page read is now 293us,
>>> 6.99MB/s (was 385us, 5.31MB/s). oob_first is probably the best case
>>> improvement.
>>>
>>> Signed-off-by: Nick Thompson <nick.thompson at ge.com>
>> 
>> Also tested on Canyonlands (460EX); here I actually see a slightj
>> improvement (5.5% faster, i. e. time to read 126 MB from NAND goes
>> down from 28.8 to 27.2 seconds (4.4 -> 4.6 MiB/s).
>> 
>> Tested-by: Wolfgang Denk <wd at denx.de>
> 
> Hi Wolfgang,
> 
> Thanks again.
> 
> It seems the raw page data transfer rate is quite low on that board.
> The patch saves time between page data transfers, so the percentage
> improvement seen is better if you can get the page data out quicker.
> 
> The default read_buf (and write_buf) in nand_base.c are safe, but slow.
> I put in davinci specific optimised versions (DMA or multibyte read
> ticks might be used) to double my raw transfer rate. Without that, my
> measurements would show ~15% improvement only.
> 
> In total on da830evm I'm getting a >300% speed improvement. 1.69MB/s
> changes to 6.99MB/s. (5.31MB/s without this patch.)
> 
> Nick.
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> 
> 

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