[PATCH 0/2] Improve GTA02 NAND read performance by 41%

[Harald Welte]

Hi Micael,

On Mon, Oct 20, 2008 at 10:29:24PM +0200, Micael Henriksson wrote:
 
> Does this only concern GTA02 or can a similar thing be applied to GTA01 as well?

GTA01 uses an external flash memory which has different timings.  However,
it is certainly useful to investigate if the timings are optimal or not.

According to the data sheet, the following timings should be sufficient:

Tacls = 0ns, Twrph0 = 25ns, Twrph1 = 25ns

The GTA01 kernel currently uses 20ns / 60ns / 20ns (according to
gta01_nand_info).  So there should be room for improvement, too!

However, since the HCLK runs at 133MHz on GTA01, there's a 7.52ns granularity,
i.e. the actual values used should be
* old kernel: Tacls = 3 (22.53ns), Twrph0 = 8 (60.16ns), Twrph1 = 3 (22.53ns)
* optimized: Tacls = 0 (0ns), Twrph0 = 4 (30.08ns), Twrph1 = 4 (30.08ns)

It _should_ even be possible to reduce Twrph0 to 3 (22.53ns), resulting in a
total cycle time of 52.64ns, well above the 45ns minimum requirement of the
NAND flash.

My current work for Swisscom limits me to GTA02, so I cannot test this myself.
But it should be very straight-forward to test it by yourself with a custom
kernel.

Cheers,
-- 
- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
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