]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
i2c: OMAP2/3: Fix scll/sclh calculations
authorAaro Koskinen <aaro.koskinen@nokia.com>
Wed, 27 May 2009 14:54:45 +0000 (17:54 +0300)
committerBen Dooks <ben-linux@fluff.org>
Sat, 13 Jun 2009 09:39:25 +0000 (10:39 +0100)
commitbaf46b4e378d7950dff7ba30cfd50ff585987cb4
tree571bd77cb953d1fc6a206c250b3cf8dd4718546f
parente0cd2dd5dd2b7c6512e46ce0b4f119cd7b0c74a4
i2c: OMAP2/3: Fix scll/sclh calculations

Fix scll/sclh calculations for HS and fast modes. Currently the driver
uses equal (roughly) low/high times which will result in too short
low time.

OMAP3430 TRM gives the following equations:

F/S: tLow  = (scll + 7) * internal_clk
     tHigh = (sclh + 5) * internal_clk
HS:  tLow  = (scll + 7) * fclk
     tHigh = (sclh + 5) * fclk

Furthermore, the I2C specification sets the following minimum values
for HS tLow/tHigh for capacitive bus loads 100 pF (maximum speed 3400)
and 400 pF (maximum speed 1700):

speed tLow tHigh
3400 160 ns 60 ns
1700 320 ns 120 ns

and for F/S:

speed tLow tHigh
400 1300 ns 600 ns
100 4700 ns 4000 ns

By using duty cycles 33/66 (HS, F) and 50/50 (S) we stay above these
minimum values.

Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
drivers/i2c/busses/i2c-omap.c