Move target-* CPU file into a target/ folder

We've currently got 18 architectures in QEMU, and thus 18 target-xxx
folders in the root folder of the QEMU source tree. More architectures
(e.g. RISC-V, AVR) are likely to be included soon, too, so the main
folder of the QEMU sources slowly gets quite overcrowded with the
target-xxx folders.
To disburden the main folder a little bit, let's move the target-xxx
folders into a dedicated target/ folder, so that target-xxx/ simply
becomes target/xxx/ instead.

Acked-by: Laurent Vivier <laurent@vivier.eu> [m68k part]
Acked-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de> [tricore part]
Acked-by: Michael Walle <michael@walle.cc> [lm32 part]
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> [s390x part]
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> [s390x part]
Acked-by: Eduardo Habkost <ehabkost@redhat.com> [i386 part]
Acked-by: Artyom Tarasenko <atar4qemu@gmail.com> [sparc part]
Acked-by: Richard Henderson <rth@twiddle.net> [alpha part]
Acked-by: Max Filippov <jcmvbkbc@gmail.com> [xtensa part]
Reviewed-by: David Gibson <david@gibson.dropbear.id.au> [ppc part]
Acked-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com> [cris&microblaze part]
Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn> [unicore32 part]
Signed-off-by: Thomas Huth <thuth@redhat.com>

1 files changed, 150 insertions, 0 deletions

diff --git a/target/sh4/README.sh4 b/target/sh4/README.sh4
new file mode 100644
index 0000000000..a192ca7540
--- /dev/null
+++ b/target/sh4/README.sh4
@@ -0,0 +1,150 @@
+qemu target:   sh4
+author:        Samuel Tardieu <sam@rfc1149.net>
+last modified: Tue Dec  6 07:22:44 CET 2005
+
+The sh4 target is not ready at all yet for integration in qemu. This
+file describes the current state of implementation.
+
+Most places requiring attention and/or modification can be detected by
+looking for "XXXXX" or "abort()".
+
+The sh4 core is located in target/sh4/*, while the 7750 peripheral
+features (IO ports for example) are located in hw/sh7750.[ch]. The
+main board description is in hw/shix.c, and the NAND flash in
+hw/tc58128.[ch].
+
+All the shortcomings indicated here will eventually be resolved. This
+is a work in progress. Features are added in a semi-random order: if a
+point is blocking to progress on booting the Linux kernel for the shix
+board, it is addressed first; if feedback is necessary and no progress
+can be made on blocking points until it is received, a random feature
+is worked on.
+
+Goals
+-----
+
+The primary model being worked on is the soft MMU target to be able to
+emulate the Shix 2.0 board by Alexis Polti, described at
+https://web.archive.org/web/20070917001736/http://perso.enst.fr/~polti/realisations/shix20/
+
+Ultimately, qemu will be coupled with a system C or a verilog
+simulator to simulate the whole board functionalities.
+
+A sh4 user-mode has also somewhat started but will be worked on
+afterwards. The goal is to automate tests for GNAT (GNU Ada) compiler
+that I ported recently to the sh4-linux target.
+
+Registers
+---------
+
+16 general purpose registers are available at any time. The first 8
+registers are banked and the non-directly visible ones can be accessed
+by privileged instructions. In qemu, we define 24 general purpose
+registers and the code generation use either [0-7]+[8-15] or
+[16-23]+[8-15] depending on the MD and RB flags in the sr
+configuration register.
+
+Instructions
+------------
+
+Most sh4 instructions have been implemented. The missing ones at this
+time are:
+  - FPU related instructions
+  - LDTLB to load a new MMU entry
+  - SLEEP to put the processor in sleep mode
+
+Most instructions could be optimized a lot. This will be worked on
+after the current model is fully functional unless debugging
+convenience requires that it is done early.
+
+Many instructions did not have a chance to be tested yet. The plan is
+to implement unit and regression testing of those in the future.
+
+MMU
+---
+
+The MMU is implemented in the sh4 core. MMU management has not been
+tested at all yet. In the sh7750, it can be manipulated through memory
+mapped registers and this part has not yet been implemented.
+
+Exceptions
+----------
+
+Exceptions are implemented as described in the sh4 reference manual
+but have not been tested yet. They do not use qemu EXCP_ features
+yet.
+
+IRQ
+---
+
+IRQ are not implemented yet.
+
+Peripheral features
+-------------------
+
+  + Serial ports
+
+Configuration and use of the first serial port (SCI) without
+interrupts is supported. Input has not yet been tested.
+
+Configuration of the second serial port (SCIF) is supported. FIFO
+handling infrastructure has been started but is not completed yet.
+
+  + GPIO ports
+
+GPIO ports have been implemented. A registration function allows
+external modules to register interest in some port changes (see
+hw/tc58128.[ch] for an example) and will be called back. Interrupt
+generation is not yet supported but some infrastructure is in place
+for this purpose. Note that in the current model a peripheral module
+cannot directly simulate a H->L->H input port transition and have an
+interrupt generated on the low level.
+
+  + TC58128 NAND flash
+
+TC58128 NAND flash is partially implemented through GPIO ports. It
+supports reading from flash.
+
+GDB
+---
+
+GDB remote target support has been implemented and lightly tested.
+
+Files
+-----
+
+File names are hardcoded at this time. The bootloader must be stored in
+shix_bios.bin in the current directory. The initial Linux image must
+be stored in shix_linux_nand.bin in the current directory in NAND
+format. Test files can be obtained from
+http://perso.enst.fr/~polti/robot/ as well as the various datasheets I
+use.
+
+qemu disk parameter on the command line is unused. You can supply any
+existing image and it will be ignored. As the goal is to simulate an
+embedded target, it is not clear how this parameter will be handled in
+the future.
+
+To build an ELF kernel image from the NAND image, 16 bytes have to be
+stripped off the end of every 528 bytes, keeping only 512 of them. The
+following Python code snippet does it:
+
+#! /usr/bin/python
+
+def denand (infd, outfd):
+    while True:
+        d = infd.read (528)
+        if not d: return
+        outfd.write (d[:512])
+
+if __name__ == '__main__':
+    import sys
+    denand (open (sys.argv[1], 'rb'),
+            open (sys.argv[2], 'wb'))
+
+Style isssues
+-------------
+
+There is currently a mix between my style (space before opening
+parenthesis) and qemu style. This will be resolved before final
+integration is proposed.