Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

5 files changed, 353 insertions, 0 deletions

diff --git a/Documentation/arm/nwfpe/index.rst b/Documentation/arm/nwfpe/index.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+===================================
+NetWinder's floating point emulator
+===================================
+
+.. toctree::
+   :maxdepth: 1
+
+   nwfpe
+   netwinder-fpe
+   notes
+   todo
diff --git a/Documentation/arm/nwfpe/netwinder-fpe.rst b/Documentation/arm/nwfpe/netwinder-fpe.rst
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+=============
+Current State
+=============
+
+The following describes the current state of the NetWinder's floating point
+emulator.
+
+In the following nomenclature is used to describe the floating point
+instructions.  It follows the conventions in the ARM manual.
+
+::
+
+  <S|D|E> = <single|double|extended>, no default
+  {P|M|Z} = {round to +infinity,round to -infinity,round to zero},
+            default = round to nearest
+
+Note: items enclosed in {} are optional.
+
+Floating Point Coprocessor Data Transfer Instructions (CPDT)
+------------------------------------------------------------
+
+LDF/STF - load and store floating
+
+<LDF|STF>{cond}<S|D|E> Fd, Rn
+<LDF|STF>{cond}<S|D|E> Fd, [Rn, #<expression>]{!}
+<LDF|STF>{cond}<S|D|E> Fd, [Rn], #<expression>
+
+These instructions are fully implemented.
+
+LFM/SFM - load and store multiple floating
+
+Form 1 syntax:
+<LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn]
+<LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn, #<expression>]{!}
+<LFM|SFM>{cond}<S|D|E> Fd, <count>, [Rn], #<expression>
+
+Form 2 syntax:
+<LFM|SFM>{cond}<FD,EA> Fd, <count>, [Rn]{!}
+
+These instructions are fully implemented.  They store/load three words
+for each floating point register into the memory location given in the
+instruction.  The format in memory is unlikely to be compatible with
+other implementations, in particular the actual hardware.  Specific
+mention of this is made in the ARM manuals.
+
+Floating Point Coprocessor Register Transfer Instructions (CPRT)
+----------------------------------------------------------------
+
+Conversions, read/write status/control register instructions
+
+FLT{cond}<S,D,E>{P,M,Z} Fn, Rd          Convert integer to floating point
+FIX{cond}{P,M,Z} Rd, Fn                 Convert floating point to integer
+WFS{cond} Rd                            Write floating point status register
+RFS{cond} Rd                            Read floating point status register
+WFC{cond} Rd                            Write floating point control register
+RFC{cond} Rd                            Read floating point control register
+
+FLT/FIX are fully implemented.
+
+RFS/WFS are fully implemented.
+
+RFC/WFC are fully implemented.  RFC/WFC are supervisor only instructions, and
+presently check the CPU mode, and do an invalid instruction trap if not called
+from supervisor mode.
+
+Compare instructions
+
+CMF{cond} Fn, Fm        Compare floating
+CMFE{cond} Fn, Fm       Compare floating with exception
+CNF{cond} Fn, Fm        Compare negated floating
+CNFE{cond} Fn, Fm       Compare negated floating with exception
+
+These are fully implemented.
+
+Floating Point Coprocessor Data Instructions (CPDT)
+---------------------------------------------------
+
+Dyadic operations:
+
+ADF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - add
+SUF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - subtract
+RSF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse subtract
+MUF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - multiply
+DVF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - divide
+RDV{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse divide
+
+These are fully implemented.
+
+FML{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast multiply
+FDV{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast divide
+FRD{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - fast reverse divide
+
+These are fully implemented as well.  They use the same algorithm as the
+non-fast versions.  Hence, in this implementation their performance is
+equivalent to the MUF/DVF/RDV instructions.  This is acceptable according
+to the ARM manual.  The manual notes these are defined only for single
+operands, on the actual FPA11 hardware they do not work for double or
+extended precision operands.  The emulator currently does not check
+the requested permissions conditions, and performs the requested operation.
+
+RMF{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - IEEE remainder
+
+This is fully implemented.
+
+Monadic operations:
+
+MVF{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - move
+MNF{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - move negated
+
+These are fully implemented.
+
+ABS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - absolute value
+SQT{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - square root
+RND{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - round
+
+These are fully implemented.
+
+URD{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - unnormalized round
+NRM{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - normalize
+
+These are implemented.  URD is implemented using the same code as the RND
+instruction.  Since URD cannot return a unnormalized number, NRM becomes
+a NOP.
+
+Library calls:
+
+POW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - power
+RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power
+POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2)
+
+LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10
+LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e
+EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent
+SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine
+COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine
+TAN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - tangent
+ASN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arcsine
+ACS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arccosine
+ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent
+
+These are not implemented.  They are not currently issued by the compiler,
+and are handled by routines in libc.  These are not implemented by the FPA11
+hardware, but are handled by the floating point support code.  They should
+be implemented in future versions.
+
+Signalling:
+
+Signals are implemented.  However current ELF kernels produced by Rebel.com
+have a bug in them that prevents the module from generating a SIGFPE.  This
+is caused by a failure to alias fp_current to the kernel variable
+current_set[0] correctly.
+
+The kernel provided with this distribution (vmlinux-nwfpe-0.93) contains
+a fix for this problem and also incorporates the current version of the
+emulator directly.  It is possible to run with no floating point module
+loaded with this kernel.  It is provided as a demonstration of the
+technology and for those who want to do floating point work that depends
+on signals.  It is not strictly necessary to use the module.
+
+A module (either the one provided by Russell King, or the one in this
+distribution) can be loaded to replace the functionality of the emulator
+built into the kernel.
diff --git a/Documentation/arm/nwfpe/notes.rst b/Documentation/arm/nwfpe/notes.rst
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+Notes
+=====
+
+There seems to be a problem with exp(double) and our emulator.  I haven't
+been able to track it down yet.  This does not occur with the emulator
+supplied by Russell King.
+
+I also found one oddity in the emulator.  I don't think it is serious but
+will point it out.  The ARM calling conventions require floating point
+registers f4-f7 to be preserved over a function call.  The compiler quite
+often uses an stfe instruction to save f4 on the stack upon entry to a
+function, and an ldfe instruction to restore it before returning.
+
+I was looking at some code, that calculated a double result, stored it in f4
+then made a function call. Upon return from the function call the number in
+f4 had been converted to an extended value in the emulator.
+
+This is a side effect of the stfe instruction.  The double in f4 had to be
+converted to extended, then stored.  If an lfm/sfm combination had been used,
+then no conversion would occur.  This has performance considerations.  The
+result from the function call and f4 were used in a multiplication.  If the
+emulator sees a multiply of a double and extended, it promotes the double to
+extended, then does the multiply in extended precision.
+
+This code will cause this problem:
+
+double x, y, z;
+z = log(x)/log(y);
+
+The result of log(x) (a double) will be calculated, returned in f0, then
+moved to f4 to preserve it over the log(y) call.  The division will be done
+in extended precision, due to the stfe instruction used to save f4 in log(y).
diff --git a/Documentation/arm/nwfpe/nwfpe.rst b/Documentation/arm/nwfpe/nwfpe.rst
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+Introduction
+============
+
+This directory contains the version 0.92 test release of the NetWinder
+Floating Point Emulator.
+
+The majority of the code was written by me, Scott Bambrough It is
+written in C, with a small number of routines in inline assembler
+where required.  It was written quickly, with a goal of implementing a
+working version of all the floating point instructions the compiler
+emits as the first target.  I have attempted to be as optimal as
+possible, but there remains much room for improvement.
+
+I have attempted to make the emulator as portable as possible.  One of
+the problems is with leading underscores on kernel symbols.  Elf
+kernels have no leading underscores, a.out compiled kernels do.  I
+have attempted to use the C_SYMBOL_NAME macro wherever this may be
+important.
+
+Another choice I made was in the file structure.  I have attempted to
+contain all operating system specific code in one module (fpmodule.*).
+All the other files contain emulator specific code.  This should allow
+others to port the emulator to NetBSD for instance relatively easily.
+
+The floating point operations are based on SoftFloat Release 2, by
+John Hauser.  SoftFloat is a software implementation of floating-point
+that conforms to the IEC/IEEE Standard for Binary Floating-point
+Arithmetic.  As many as four formats are supported: single precision,
+double precision, extended double precision, and quadruple precision.
+All operations required by the standard are implemented, except for
+conversions to and from decimal.  We use only the single precision,
+double precision and extended double precision formats.  The port of
+SoftFloat to the ARM was done by Phil Blundell, based on an earlier
+port of SoftFloat version 1 by Neil Carson for NetBSD/arm32.
+
+The file README.FPE contains a description of what has been implemented
+so far in the emulator.  The file TODO contains a information on what
+remains to be done, and other ideas for the emulator.
+
+Bug reports, comments, suggestions should be directed to me at
+<scottb@netwinder.org>.  General reports of "this program doesn't
+work correctly when your emulator is installed" are useful for
+determining that bugs still exist; but are virtually useless when
+attempting to isolate the problem.  Please report them, but don't
+expect quick action.  Bugs still exist.  The problem remains in isolating
+which instruction contains the bug.  Small programs illustrating a specific
+problem are a godsend.
+
+Legal Notices
+-------------
+
+The NetWinder Floating Point Emulator is free software.  Everything Rebel.com
+has written is provided under the GNU GPL.  See the file COPYING for copying
+conditions.  Excluded from the above is the SoftFloat code.  John Hauser's
+legal notice for SoftFloat is included below.
+
+-------------------------------------------------------------------------------
+
+SoftFloat Legal Notice
+
+SoftFloat was written by John R. Hauser.  This work was made possible in
+part by the International Computer Science Institute, located at Suite 600,
+1947 Center Street, Berkeley, California 94704.  Funding was partially
+provided by the National Science Foundation under grant MIP-9311980.  The
+original version of this code was written as part of a project to build
+a fixed-point vector processor in collaboration with the University of
+California at Berkeley, overseen by Profs. Nelson Morgan and John Wawrzynek.
+
+THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE.  Although reasonable effort
+has been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT
+TIMES RESULT IN INCORRECT BEHAVIOR.  USE OF THIS SOFTWARE IS RESTRICTED TO
+PERSONS AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ANY
+AND ALL LOSSES, COSTS, OR OTHER PROBLEMS ARISING FROM ITS USE.
+-------------------------------------------------------------------------------
diff --git a/Documentation/arm/nwfpe/todo.rst b/Documentation/arm/nwfpe/todo.rst
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+TODO LIST
+=========
+
+::
+
+  POW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - power
+  RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power
+  POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2)
+
+  LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10
+  LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e
+  EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent
+  SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine
+  COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine
+  TAN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - tangent
+  ASN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arcsine
+  ACS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arccosine
+  ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent
+
+These are not implemented.  They are not currently issued by the compiler,
+and are handled by routines in libc.  These are not implemented by the FPA11
+hardware, but are handled by the floating point support code.  They should
+be implemented in future versions.
+
+There are a couple of ways to approach the implementation of these.  One
+method would be to use accurate table methods for these routines.  I have
+a couple of papers by S. Gal from IBM's research labs in Haifa, Israel that
+seem to promise extreme accuracy (in the order of 99.8%) and reasonable speed.
+These methods are used in GLIBC for some of the transcendental functions.
+
+Another approach, which I know little about is CORDIC.  This stands for
+Coordinate Rotation Digital Computer, and is a method of computing
+transcendental functions using mostly shifts and adds and a few
+multiplications and divisions.  The ARM excels at shifts and adds,
+so such a method could be promising, but requires more research to
+determine if it is feasible.
+
+Rounding Methods
+----------------
+
+The IEEE standard defines 4 rounding modes.  Round to nearest is the
+default, but rounding to + or - infinity or round to zero are also allowed.
+Many architectures allow the rounding mode to be specified by modifying bits
+in a control register.  Not so with the ARM FPA11 architecture.  To change
+the rounding mode one must specify it with each instruction.
+
+This has made porting some benchmarks difficult.  It is possible to
+introduce such a capability into the emulator.  The FPCR contains
+bits describing the rounding mode.  The emulator could be altered to
+examine a flag, which if set forced it to ignore the rounding mode in
+the instruction, and use the mode specified in the bits in the FPCR.
+
+This would require a method of getting/setting the flag, and the bits
+in the FPCR.  This requires a kernel call in ArmLinux, as WFC/RFC are
+supervisor only instructions.  If anyone has any ideas or comments I
+would like to hear them.
+
+NOTE:
+ pulled out from some docs on ARM floating point, specifically
+ for the Acorn FPE, but not limited to it:
+
+ The floating point control register (FPCR) may only be present in some
+ implementations: it is there to control the hardware in an implementation-
+ specific manner, for example to disable the floating point system.  The user
+ mode of the ARM is not permitted to use this register (since the right is
+ reserved to alter it between implementations) and the WFC and RFC
+ instructions will trap if tried in user mode.
+
+ Hence, the answer is yes, you could do this, but then you will run a high
+ risk of becoming isolated if and when hardware FP emulation comes out
+
+		-- Russell.