Author: wmb Date: Wed Nov 9 06:00:22 2011 New Revision: 2678 URL: http://tracker.coreboot.org/trac/openfirmware/changeset/2678
Log: OLPC XO-1.75 - fixed high speed TWSI operation based on new information about how the registers work.
Modified: cpu/arm/mmp2/twsi.fth
Modified: cpu/arm/mmp2/twsi.fth ============================================================================== --- cpu/arm/mmp2/twsi.fth Tue Nov 8 20:20:58 2011 (r2677) +++ cpu/arm/mmp2/twsi.fth Wed Nov 9 06:00:22 2011 (r2678) @@ -15,11 +15,13 @@ : sr@ ( -- n ) twsi-chip h# 18 + io@ ; : sar@ ( -- n ) twsi-chip h# 20 + io@ ; : lcr@ ( -- n ) twsi-chip h# 28 + io@ ; +: wcr@ ( -- n ) twsi-chip h# 30 + io@ ; : dbr! ( n -- ) twsi-chip h# 08 + io! ; : cr! ( n -- ) twsi-chip h# 10 + io! ; : sr! ( n -- ) twsi-chip h# 18 + io! ; : sar! ( n -- ) twsi-chip h# 20 + io! ; : lcr! ( n -- ) twsi-chip h# 28 + io! ; +: wcr! ( -- n ) twsi-chip h# 30 + io! ;
create channel-bases h# 011000 , h# 031000 , h# 032000 , h# 033000 , h# 033800 , h# 034000 , @@ -58,6 +60,10 @@
h# 1000 constant BBU_TWSI_TimeOut \ TWSI bus timeout loop counter value
+d# 26 constant ftwsi-mhz \ +d# 1400 constant tlow-nsec \ The I2C spec calls for Tlow >= 1300 ns +ftwsi-mhz tlow-nsec d# 1000 */ constant tlow-ticks + bbu_ICR_IUE bbu_ICR_SCLE or value cr-set \ bits to maintain as set : init-twsi-channel ( channel# -- ) set-twsi-channel @@ -67,6 +73,9 @@ cr-set cr! \ Release the reset 0 sar! \ Set host slave address 0 cr! \ Disable interrupts + \ The COUNT field of TWSI_WCR establishes a minimum value for the SCL low time. + \ The minimum Tlow is the clock period * (12 + 2*COUNT) + wcr@ h# 1f invert and tlow-ticks d# 12 - 2/ or wcr! \ Setup and hold times ; : init-twsi ( -- ) 7 1 do i init-twsi-channel loop @@ -177,25 +186,25 @@ twsi-out ;
-: set-bus-standard cr-set h# fffe7fff and to cr-set ; -: set-bus-fast cr-set h# fffe7fff and h# 8000 or to cr-set ;
-\ The dividends below (12,600,000 and 11,600,000) are chosen to give the -\ same values that the LCR defaults to for the data rates 100,000 and 400,000 -\ The TWSI input clock is the 26 MHz VCXO, and the divided value generates -\ both the low phase and the high phase, so you would think that the dividend -\ should be 13,000,000 (half of 26M), but that doesn't give the right result. -\ Perhaps there is an additive factor in the divisor; the manual is quite vague. +: set-bus-standard cr-set h# 18000 invert and to cr-set ; +: set-bus-fast cr-set h# 18000 invert and h# 8000 or to cr-set ; + : set-bus-speed ( hz -- ) \ Useful range is 25K .. 400K - 100K and 400K are typical child-address set-twsi-target ( hz ) - dup d# 100,000 <= if ( hz ) - set-bus-standard ( hz ) - d# 12,600,000 swap / h# 1ff min h# 7e max ( divisor ) + ftwsi-mhz d# 1,000,000 2 pick */ ( hz ticks ) + swap d# 100,000 <= if ( ticks ) + \ In slow mode, Thi = Tclk * (8+slv), Tlow = Tclk * (1+slv) + 9 - 2/ 1+ ( slv ) lcr@ h# 1ff invert and or lcr! ( ) - else ( hz ) - set-bus-fast ( hz ) - d# 11,600,000 swap / h# 1ff min h# 1d max ( divisor ) - lcr@ h# 3.fe00 invert and swap 9 lshift or lcr! ( ) + set-bus-standard ( ) + else ( ticks ) + \ (The information below is poorly documented and was determined empirically) + \ In fast mode, Thi = Tclk * (10+flv), Tlo = Tclk * max(1+flv, tlow_ticks)) + dup d# 11 - 2/ 1+ tlow-ticks max ( ticks ticks-low ) + - d# 10 - ( flv ) + 9 lshift lcr@ h# 3.fe00 invert and or lcr! ( ) + set-bus-fast ( ) then ( ) ; : decode-unit ( adr len -- low high ) parse-2int ;