xtensa: add support for the 'xtfpga' evaluation board

The 'xtfpga' board is actually a set of FPGA evaluation boards that
can be configured to run an Xtensa processor.

 - Avnet Xilinx LX60
 - Avnet Xilinx LX110
 - Avnet Xilinx LX200
 - Xilinx ML605
 - Xilinx KC705

These boards share the same components (open-ethernet, ns16550 serial,
lcd display, flash, etc.).

Signed-off-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

1 files changed, 125 insertions, 0 deletions

diff --git a/board/cadence/xtfpga/README b/board/cadence/xtfpga/README
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+		Tensilica 'xtfpga' Evaluation Boards
+		====================================
+
+Tensilica's 'xtfpga' evaluation boards are actually a set of different
+boards that share configurations. The following is a list of supported
+hardware by this board type:
+
+- XT-AV60  / LX60
+- XT-AV110 / LX110
+- XT-AV200 / LX200
+- ML605
+- KC705
+
+All boards provide the following common configurations:
+
+- An Xtensa or Diamond processor core.
+- An on-chip-debug (OCD) JTAG interface.
+- A 16550 compatible UART and serial port.
+- An OpenCores Wishbone 10/100-base-T ethernet interface.
+- A 32 char two line LCD display. (except for the LX200)
+
+LX60/LX110/LX200:
+
+- Virtex-4 (XC4VLX60 / XCV4LX200) / Virtext-5 (XC5VLX110)
+- 128MB / 64MB (LX60) memory
+- 16MB / 4MB (LX60) Linear Flash
+
+ML605
+
+- Virtex-6 (XC6VLX240T)
+- 512MB DDR3 memory
+- 16MB Linear BPI Flash
+
+KC705 (Xilinx)
+
+- Kintex-7 XC7K325T FPGA
+- 1GB DDR3 memory
+- 128MB Linear BPI Flash
+
+
+Setting up the Board
+--------------------
+
+The serial port defaults to 115200 baud, no parity and 1 stop bit.
+A terminal emulator must be set accordingly to see the U-Boot prompt.
+
+
+Board Configurations LX60/LX110/LX200/ML605/KC705
+-------------------------------------------------
+
+The LX60/LX110/LX200/ML605 contain an 8-way DIP switch that controls
+the boot mapping and selects from a range of default ethernet MAC
+addresses.
+
+Boot Mapping (DIP switch 8):
+
+    DIP switch 8 maps the system ROM address space (in which the
+    reset vector resides) to either SRAM (off, 0, down) or Flash
+    (on, 1, up).  This mapping is implemented in the FPGA bitstream
+    and cannot be disabled by software, therefore DIP switch 8 is no
+    available for application use. Note DIP switch 7 is reserved by
+    Tensilica for future possible hardware use.
+
+    Mapping to SRAM allows U-Boot to be debugged with an OCD/JTAG
+    tool such as the Xtensa OCD Daemon connected via a suppored probe.
+    See the tools documentation for supported probes and how to
+    connect them.  Be aware that the board has only 128 KB of SRAM,
+    therefore U-Boot must fit within this space to debug an image
+    intended for the Flash.  This issues is discussed in a separate
+    section toward the end.
+
+    Mapping to flash allows U-Boot to start on reset, provided it
+    has been programmed into the first two 64 KB sectors of the Flash.
+
+    The Flash is always mapped at a device (memory mapped I/O) address
+    (the address is board specific and is expressed as CFG_FLASH_BASE).
+    The device address is used by U-Boot to program the flash, and may
+    be used to specify an application to run or U-Boot image to boot.
+
+Default MAC Address (DIP switches 1-6):
+
+    When the board is first powered on, or after the environment has
+    been reinitialized, the ethernet MAC address receives a default
+    value whose least significant 6 bits come from DIP switches 1-6.
+    The default is 00:50:C2:13:6F:xx where xx ranges from 0..3F
+    according to the DIP switches, where "on"==1 and "off"==0, and
+    switch 1 is the least-significant bit.
+
+    After initial startup, the MAC address is stored in the U-Boot
+    environment variable 'ethaddr'. The user may change this to any
+    other address with the "setenv" comamnd. After the environment
+    has been saved to Flash by the "saveenv" command, this will be
+    used and the DIP switches no longer consulted. DIP swithes 1-6
+    may then be used for application purposes.
+
+The KC705 board contains 4-way DIP switch, way 1 is the boot mapping
+switch and ways 2-4 control the low three bits of the MAC address.
+
+
+Limitation of SDRAM Size for OCD Debugging on the LX60
+------------------------------------------------------
+
+The XT-AV60 board has only 128 KB of SDRAM that can be mapped
+to the system ROM address space for debugging a ROM image under
+OCD/JTAG. This limits the useful size of U-Boot to 128 KB (0x20000)
+or the first 2 sectors of the flash.
+
+This can pose a problem if all the sources are compiled with -O0
+for debugging. The code size is then too large, in which case it
+would be necessary to temporarily alter the linker script to place
+the load addresses (LMA) in the RAM (VMA) so that OCD loads U-Boot
+directly there and does not unpack. In practice this is not really
+necessary as long as only a limited set of sources need to be
+debugged, because the image can still fit into the 128 KB SRAM.
+
+The recommended procedure for debugging is to first build U-Boot
+with the default optimization level (-Os), and then touch and
+rebuild incrementally with -O0 so that only the touched sources
+are recompiled with -O0. To build with -O0, pass it in the KCFLAGS
+variable to make.
+
+Because this problem is easy to fall into and difficult to debug
+if one doesn't expect it, the linker script provides a link-time
+check and fatal error message if the image size exceeds 128 KB.
+