Hi everyone, I am seeing a strange issue that someone may have bumped into before. I am running a modified version of Freescale's v2008.10 U-boot release from the December 2008 LTIB package on our 8572E based board. Under normal reset conditions (power up or reset switch), the board boots and runs fine including loading and running linux.
If however I connect a JTAG emulator (WindRiver probe) and reset the target using the "inn" command, which should reset the core without loading any registers, and follow up with a "go" command which starts the core fetching from the reset vector, the read of the DIMM SPD data fails. Further analysis shows that the serial EEPROM doesn't answer the bell because the I2C bus clock is running at something close to 4MHz instead of the 400KHz specified. While the target is in this state, I can use the emulator to jack up the I2C divider to its max (0x3F) and run a dummy I2C read. Changing the divider does have an effect on the I2C clock frequency. It is almost as though the input clock to the I2C block is running way too fast. From the Freescale documentation, the I2C clock is half the CCB clock. The UART prints without problem so the baud rate dividers and CCB clock frequency would seem to be all right. The U-boot banner portion which reads all of the clock ratios is not different between and hard reset and an emulator reset. A read of the PORPLLSR returns the correct ratios even when the I2C clock speed is way off. I have an older version of U-boot for the board which is based of the initial port that Kumar did (no MP support, etc.). With this version of U-boot in flash, the "inn" "go" sequence works fine. The only thing that I can think of is that the older U-boot has a different init sequence. Does anyone know of way to ensure that the I2C input clock is stable before attempting I2C operations? Thanks in advance, Scott ___________________________________________________________________ Scott N. Coulter Senior Software Engineer Cyclone Microsystems 370 James Street Phone: 203.786.5536 ext. 118 New Haven, CT 06513-3051 Email: scott.coul...@cyclone.com U.S.A. Web: http://www.cyclone.com ___________________________________________________________________ _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
