Embedded module TQMa28 - PTXdist Linux BSP documentation

Known Issues

RS485 bus block in half-duplex mode
Affects	RS485 via UARTx
Issue	During i.MX28 reset the UARTx.CTS# pin is low by default (CPU internal pull down)
Effect	Using the MBa28 RS485 circuitry in a half-duplex slave device or half-duplex multi-master environment may block the RS485 bus during i.MX28 reset. The bus is released as soon as the UARTx.CTS# pin is properly configured by software (e.g. U-Boot, Linux, etc.)
Solution / Workaround	Add a 10k pull up to the UARTx.CTS# signal on carrier board

Affected hardware revisions: TQMa28 module REV0200
Impact: eMMC drive strength (card to host) is too high in card default configuration. This degrades signal integrity and has the potential to degrade the lifetime.
Solution: use only new linux / u-boot from BSP REV0106 or port the required changes to your bootloader /operating system.
Details: Starting with hardware REV0200 a new eMMC type with better performance characteristics is used on TQMa28. This eMMC features a configurable drive strength (MMC CMD4 - SET_DSR, see JEDEC Standard No. 84-A441, Table 22)
To keep signal integrity and prevent degrading the lifetime of the processor the following configuration step for the eMMC must be implemented:
- Write 0x0100 + 16 Stuff bits using CMD4 to the card everytime the card is selected using CMD7

The current state of the changes needed in BSP REV0106 for:
- U-Boot 2013.04 (TQMa28/28L): modifies device tree before booting linux to incorporate DSR value for eMMC value
- U-Boot 2009.08 (TQMa28-fsl): modifies linux command-line to incorporate DSR value for eMMC value
- Linux 3.10 (TQMa28/28L): value of DSR parsed from device tree property
- Linux 2.6.35 (TQMa28-fsl): value of DSR parsed from kernel command-line

Both device tree and command-line implement the value as “tq,dsr”.

Affected Revisions: 0100, 0101
Issue: Unable to extract sizes of images on SD card ⇒ Unable to calculate required sectors to save image
Workaround: whole uboot/kernel partitions copied

Affected Revisions: 0101
Issue: The brownout value of register HW_POWER_VDDA is set to 100 mV below 1.8 V. During boot voltage drops >100mV occur. For the VDDA_BO being too close the device powers down and thus stops after the Kernel line “TCP established hash table entries”.
Workaround: Increase brownout span to 150 mV.
–> At the U-Boot prompt type: mw 80044050 0x0008260c
–> You may also automate this by changing default boot command: setenv bootcmd “mw 80044050 0x0008260c; $bootcmd”; saveenv

Affected Revisions: 0101
Issue: Ethernet link cannot be established to 10 mbit half duplex counterpart
Workaround: none - fixed in future release

Affected Revisions: 0101
Issue: GPIOs on Bank 0 are unusable as interrupt source
Workaround: Patch included into next BSP revision. See https://community.freescale.com/thread/231371

Affected Revisions: all up to 0103
Issue: “adduser X; login X” results in message “Killed”
Workaround: This issue will be fixed in BSP 0103.
Until then set Kernel config option CONFIG_DEFAULT_MMAP_MIN_ADDR to 32768. Find it at Kernel features - Low address space to protect from user allocation

Affected Revisions: BSP 0102
Issue: The Operating System does not recognize USB devices if they are plugged in before boot.
Workaround: Modify the Devicetree. Add/change at usb@80090000 the following property “dr_mode” to “dr_mode = host”