- 07 Jul, 2016 4 commits
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Simon Horman authored
Basic support for the Gen 3 R-Car M3-W SoC. Based on work for the r8a7795 and r8a7796 SoCs by Takeshi Kihara, Dirk Behme and Geert Uytterhoeven. Signed-off-by: Simon Horman <horms+renesas@verge.net.au> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
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Ramesh Shanmugasundaram authored
Adds CAN FD controller node for r8a7795. Note: CAN FD controller register base address specified in R-Car Gen3 Hardware User Manual v0.5E is incorrect. The correct address is: CAN FD - 0xe66c0000 Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Geert Uytterhoeven authored
For consistency with a57_0/a57_1 cpu nodes, and all other nodes. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Simon Horman authored
clk: renesas: Updates for v4.8 (take two) - Add support for R-Car V2H, - Add FDP1, DRIF, and thermal clocks on R-Car H3, - Correct a wrong parent clock.
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- 21 Jun, 2016 7 commits
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Khiem Nguyen authored
Signed-off-by: Khiem Nguyen <khiem.nguyen.xt@rvc.renesas.com> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
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Ramesh Shanmugasundaram authored
This patch adds DRIF module clocks for r8a7795 SoC. Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
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Geert Uytterhoeven authored
According to the latest information, the parent clock of the LVDS module clock is the S0D4 clock, not the S2D1 clock. Note that this change has no influence on actual operation, as the rcar-du LVDS encoder driver doesn't use the parent clock's rate. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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Kieran Bingham authored
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Kieran Bingham <kieran@bingham.xyz> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
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Sergei Shtylyov authored
Renesas R-Car V2H (R8A7792) clocks are handled by R-Car gen2 clock driver. Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
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Sergei Shtylyov authored
Renesas R8A7792 SoC also has the CPG MSTP clocks... Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> Acked-by: Simon Horman <horms+renesas@verge.net.au> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
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Sergei Shtylyov authored
Renesas R8A7792 SoC is a member of the R-Car gen2 family and so has CPG... Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> Acked-by: Simon Horman <horms+renesas@verge.net.au> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
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- 06 Jun, 2016 4 commits
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Geert Uytterhoeven authored
Initial support for R-Car M3-W (r8a7796), including basic core clocks, and SCIF2 (console) and INTC-AP (GIC) module clocks. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Tested-by: Simon Horman <horms+renesas@verge.net.au>
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Geert Uytterhoeven authored
Extract the code to support parts common to all members of the R-Car Gen3 SoC family into a separate file, to ease sharing among SoC-specific drivers. Note that while the cpg_pll_configs[] arrays and the selection of the config based on the MODE bits are identical on R-Car H3 and R-Car M3-W, they are not common, and may be different on other R-Car Gen3 SoCs. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Tested-by: Simon Horman <horms+renesas@verge.net.au>
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Geert Uytterhoeven authored
Add all R-Car M3-W Clock Pulse Generator Core Clock Outputs, as listed in Table 8.2b ("List of Clocks [R-Car M3-W]") of the R-Car Gen3 datasheet (rev. 0.51 + Errata for Rev051 Mar 31 2016). Note that internal CPG clocks (S0, S1, S2, S3, SDSRC, and SSPSRC) are not included, as they are used as internal clock sources only, and never referenced from DT. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Tested-by: Simon Horman <horms+renesas@verge.net.au>
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Geert Uytterhoeven authored
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: Rob Herring <robh@kernel.org> Tested-by: Simon Horman <horms+renesas@verge.net.au>
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- 30 May, 2016 9 commits
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Simon Horman authored
Drop 0x from unit address of gic as this is the desired form for a unit address. Signed-off-by: Simon Horman <horms+renesas@verge.net.au> Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
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Geert Uytterhoeven authored
Warning (unit_address_vs_reg): Node /regulator@1 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /regulator@2 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /regulator@3 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /regulator@4 has a unit name, but no reg property Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Geert Uytterhoeven authored
Warning (unit_address_vs_reg): Node /cache-controller@0 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /cache-controller@1 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,dvc/dvc@0 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,dvc/dvc@1 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@0 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@1 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@2 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@3 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@4 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@5 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@6 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@7 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@8 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,src/src@9 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@0 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@1 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@2 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@3 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@4 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@5 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@6 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@7 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@8 has a unit name, but no reg property Warning (unit_address_vs_reg): Node /soc/sound@ec500000/rcar_sound,ssi/ssi@9 has a unit name, but no reg property Move the cache-controller nodes under the cpus node, and make their unit names and reg properties match the MPIDR values. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Geert Uytterhoeven authored
Hook up the RWDT device node to the SYSC "always-on" PM Domain, for a more consistent device-power-area description in DT. Cfr. commit 38dbb45e ("arm64: dts: r8a7795: Use SYSC "always-on" PM Domain") Fixes: f43838a7ae014cba ("arm64: dts: r8a7795: Add RWDT node") Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Wolfram Sang authored
This patch enables watchdog timer for Salvator-X board. Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Acked-by: Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Wolfram Sang authored
This patch adds the RWDT device node for r8a7795. Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Niklas Söderlund authored
Add DMA properties to the I2C nodes. Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Pooya Keshavarzi authored
There are some requirements about the GIC-400 memory layout and its mapping if using 64k aligned base addresses like on r8a7795. See e.g. http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=21550029f709072aacf3b9 Map the whole memory range instead of only 0x2000. This will fix the issue that some hypervisors, e.g. Xen, fail to handle the interrupts correctly. Signed-off-by: Pooya Keshavarzi <Pooya.Keshavarzi@de.bosch.com> Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com> Acked-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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Geert Uytterhoeven authored
On the Salvator-X development board, the RTS and CTS pins of debug serial-1 port SCIF1 are wired to the CP2102 Serial-USB bridge. Reflect this in the DTS by adding the "uart-has-rtscts" property to the scif1 device node. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
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- 29 May, 2016 3 commits
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Linus Torvalds authored
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George Spelvin authored
The self-test was updated to cover zero-length strings; the function needs to be updated, too. Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: George Spelvin <linux@sciencehorizons.net> Fixes: fcfd2fbf ("fs/namei.c: Add hashlen_string() function") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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George Spelvin authored
The original name was simply hash_string(), but that conflicted with a function with that name in drivers/base/power/trace.c, and I decided that calling it "hashlen_" was better anyway. But you have to do it in two places. [ This caused build errors for architectures that don't define CONFIG_DCACHE_WORD_ACCESS - Linus ] Signed-off-by: George Spelvin <linux@sciencehorizons.net> Reported-by: Guenter Roeck <linux@roeck-us.net> Fixes: fcfd2fbf ("fs/namei.c: Add hashlen_string() function") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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- 28 May, 2016 13 commits
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Mikulas Patocka authored
The HPFS filesystem used generic_show_options to produce string that is displayed in /proc/mounts. However, there is a problem that the options may disappear after remount. If we mount the filesystem with option1 and then remount it with option2, /proc/mounts should show both option1 and option2, however it only shows option2 because the whole option string is replaced with replace_mount_options in hpfs_remount_fs. To fix this bug, implement the hpfs_show_options function that prints options that are currently selected. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Mikulas Patocka authored
Commit c8f33d0b ("affs: kstrdup() memory handling") checks if the kstrdup function returns NULL due to out-of-memory condition. However, if we are remounting a filesystem with no change to filesystem-specific options, the parameter data is NULL. In this case, kstrdup returns NULL (because it was passed NULL parameter), although no out of memory condition exists. The mount syscall then fails with ENOMEM. This patch fixes the bug. We fail with ENOMEM only if data is non-NULL. The patch also changes the call to replace_mount_options - if we didn't pass any filesystem-specific options, we don't call replace_mount_options (thus we don't erase existing reported options). Fixes: c8f33d0b ("affs: kstrdup() memory handling") Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org # v4.1+ Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Mikulas Patocka authored
Commit ce657611 ("hpfs: kstrdup() out of memory handling") checks if the kstrdup function returns NULL due to out-of-memory condition. However, if we are remounting a filesystem with no change to filesystem-specific options, the parameter data is NULL. In this case, kstrdup returns NULL (because it was passed NULL parameter), although no out of memory condition exists. The mount syscall then fails with ENOMEM. This patch fixes the bug. We fail with ENOMEM only if data is non-NULL. The patch also changes the call to replace_mount_options - if we didn't pass any filesystem-specific options, we don't call replace_mount_options (thus we don't erase existing reported options). Fixes: ce657611 ("hpfs: kstrdup() out of memory handling") Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.linux-mips.org/pub/scm/ralf/upstream-linusLinus Torvalds authored
Pull more MIPS updates from Ralf Baechle: "This is the secondnd batch of MIPS patches for 4.7. Summary: CPS: - Copy EVA configuration when starting secondary VPs. EIC: - Clear Status IPL. Lasat: - Fix a few off by one bugs. lib: - Mark intrinsics notrace. Not only are the intrinsics uninteresting, it would cause infinite recursion. MAINTAINERS: - Add file patterns for MIPS BRCM device tree bindings. - Add file patterns for mips device tree bindings. MT7628: - Fix MT7628 pinmux typos. - wled_an pinmux gpio. - EPHY LEDs pinmux support. Pistachio: - Enable KASLR VDSO: - Build microMIPS VDSO for microMIPS kernels. - Fix aliasing warning by building with `-fno-strict-aliasing' for debugging but also tracing them might result in recursion. Misc: - Add missing FROZEN hotplug notifier transitions. - Fix clk binding example for varioius PIC32 devices. - Fix cpu interrupt controller node-names in the DT files. - Fix XPA CPU feature separation. - Fix write_gc0_* macros when writing zero. - Add inline asm encoding helpers. - Add missing VZ accessor microMIPS encodings. - Fix little endian microMIPS MSA encodings. - Add 64-bit HTW fields and fix its configuration. - Fix sigreturn via VDSO on microMIPS kernel. - Lots of typo fixes. - Add definitions of SegCtl registers and use them" * 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (49 commits) MIPS: Add missing FROZEN hotplug notifier transitions MIPS: Build microMIPS VDSO for microMIPS kernels MIPS: Fix sigreturn via VDSO on microMIPS kernel MIPS: devicetree: fix cpu interrupt controller node-names MIPS: VDSO: Build with `-fno-strict-aliasing' MIPS: Pistachio: Enable KASLR MIPS: lib: Mark intrinsics notrace MIPS: Fix 64-bit HTW configuration MIPS: Add 64-bit HTW fields MAINTAINERS: Add file patterns for mips device tree bindings MAINTAINERS: Add file patterns for mips brcm device tree bindings MIPS: Simplify DSP instruction encoding macros MIPS: Add missing tlbinvf/XPA microMIPS encodings MIPS: Fix little endian microMIPS MSA encodings MIPS: Add missing VZ accessor microMIPS encodings MIPS: Add inline asm encoding helpers MIPS: Spelling fix lets -> let's MIPS: VR41xx: Fix typo MIPS: oprofile: Fix typo MIPS: math-emu: Fix typo ...
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Guenter Roeck authored
Various builds (such as i386:allmodconfig) fail with fs/binfmt_aout.c:133:2: error: expected identifier or '(' before 'return' fs/binfmt_aout.c:134:1: error: expected identifier or '(' before '}' token [ Oops. My bad, I had stupidly thought that "allmodconfig" covered this on x86-64 too, but it obviously doesn't. Egg on my face. - Linus ] Fixes: 5d22fc25 ("mm: remove more IS_ERR_VALUE abuses") Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://ftp.sciencehorizons.net/linuxLinus Torvalds authored
Pull string hash improvements from George Spelvin: "This series does several related things: - Makes the dcache hash (fs/namei.c) useful for general kernel use. (Thanks to Bruce for noticing the zero-length corner case) - Converts the string hashes in <linux/sunrpc/svcauth.h> to use the above. - Avoids 64-bit multiplies in hash_64() on 32-bit platforms. Two 32-bit multiplies will do well enough. - Rids the world of the bad hash multipliers in hash_32. This finishes the job started in commit 689de1d6 ("Minimal fix-up of bad hashing behavior of hash_64()") The vast majority of Linux architectures have hardware support for 32x32-bit multiply and so derive no benefit from "simplified" multipliers. The few processors that do not (68000, h8/300 and some models of Microblaze) have arch-specific implementations added. Those patches are last in the series. - Overhauls the dcache hash mixing. The patch in commit 0fed3ac8 ("namei: Improve hash mixing if CONFIG_DCACHE_WORD_ACCESS") was an off-the-cuff suggestion. Replaced with a much more careful design that's simultaneously faster and better. (My own invention, as there was noting suitable in the literature I could find. Comments welcome!) - Modify the hash_name() loop to skip the initial HASH_MIX(). This would let us salt the hash if we ever wanted to. - Sort out partial_name_hash(). The hash function is declared as using a long state, even though it's truncated to 32 bits at the end and the extra internal state contributes nothing to the result. And some callers do odd things: - fs/hfs/string.c only allocates 32 bits of state - fs/hfsplus/unicode.c uses it to hash 16-bit unicode symbols not bytes - Modify bytemask_from_count to handle inputs of 1..sizeof(long) rather than 0..sizeof(long)-1. This would simplify users other than full_name_hash" Special thanks to Bruce Fields for testing and finding bugs in v1. (I learned some humbling lessons about "obviously correct" code.) On the arch-specific front, the m68k assembly has been tested in a standalone test harness, I've been in contact with the Microblaze maintainers who mostly don't care, as the hardware multiplier is never omitted in real-world applications, and I haven't heard anything from the H8/300 world" * 'hash' of git://ftp.sciencehorizons.net/linux: h8300: Add <asm/hash.h> microblaze: Add <asm/hash.h> m68k: Add <asm/hash.h> <linux/hash.h>: Add support for architecture-specific functions fs/namei.c: Improve dcache hash function Eliminate bad hash multipliers from hash_32() and hash_64() Change hash_64() return value to 32 bits <linux/sunrpc/svcauth.h>: Define hash_str() in terms of hashlen_string() fs/namei.c: Add hashlen_string() function Pull out string hash to <linux/stringhash.h>
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George Spelvin authored
This will improve the performance of hash_32() and hash_64(), but due to complete lack of multi-bit shift instructions on H8, performance will still be bad in surrounding code. Designing H8-specific hash algorithms to work around that is a separate project. (But if the maintainers would like to get in touch...) Signed-off-by: George Spelvin <linux@sciencehorizons.net> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: uclinux-h8-devel@lists.sourceforge.jp
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George Spelvin authored
Microblaze is an FPGA soft core that can be configured various ways. If it is configured without a multiplier, the standard __hash_32() will require a call to __mulsi3, which is a slow software loop. Instead, use a shift-and-add sequence for the constant multiply. GCC knows how to do this, but it's not as clever as some. Signed-off-by: George Spelvin <linux@sciencehorizons.net> Cc: Alistair Francis <alistair.francis@xilinx.com> Cc: Michal Simek <michal.simek@xilinx.com>
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George Spelvin authored
This provides a multiply by constant GOLDEN_RATIO_32 = 0x61C88647 for the original mc68000, which lacks a 32x32-bit multiply instruction. Yes, the amount of optimization effort put in is excessive. :-) Shift-add chain found by Yevgen Voronenko's Hcub algorithm at http://spiral.ece.cmu.edu/mcm/gen.htmlSigned-off-by: George Spelvin <linux@sciencehorizons.net> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Greg Ungerer <gerg@linux-m68k.org> Cc: Andreas Schwab <schwab@linux-m68k.org> Cc: Philippe De Muyter <phdm@macq.eu> Cc: linux-m68k@lists.linux-m68k.org
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George Spelvin authored
This is just the infrastructure; there are no users yet. This is modelled on CONFIG_ARCH_RANDOM; a CONFIG_ symbol declares the existence of <asm/hash.h>. That file may define its own versions of various functions, and define HAVE_* symbols (no CONFIG_ prefix!) to suppress the generic ones. Included is a self-test (in lib/test_hash.c) that verifies the basics. It is NOT in general required that the arch-specific functions compute the same thing as the generic, but if a HAVE_* symbol is defined with the value 1, then equality is tested. Signed-off-by: George Spelvin <linux@sciencehorizons.net> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Greg Ungerer <gerg@linux-m68k.org> Cc: Andreas Schwab <schwab@linux-m68k.org> Cc: Philippe De Muyter <phdm@macq.eu> Cc: linux-m68k@lists.linux-m68k.org Cc: Alistair Francis <alistai@xilinx.com> Cc: Michal Simek <michal.simek@xilinx.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: uclinux-h8-devel@lists.sourceforge.jp
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George Spelvin authored
Patch 0fed3ac8 improved the hash mixing, but the function is slower than necessary; there's a 7-instruction dependency chain (10 on x86) each loop iteration. Word-at-a-time access is a very tight loop (which is good, because link_path_walk() is one of the hottest code paths in the entire kernel), and the hash mixing function must not have a longer latency to avoid slowing it down. There do not appear to be any published fast hash functions that: 1) Operate on the input a word at a time, and 2) Don't need to know the length of the input beforehand, and 3) Have a single iterated mixing function, not needing conditional branches or unrolling to distinguish different loop iterations. One of the algorithms which comes closest is Yann Collet's xxHash, but that's two dependent multiplies per word, which is too much. The key insights in this design are: 1) Barring expensive ops like multiplies, to diffuse one input bit across 64 bits of hash state takes at least log2(64) = 6 sequentially dependent instructions. That is more cycles than we'd like. 2) An operation like "hash ^= hash << 13" requires a second temporary register anyway, and on a 2-operand machine like x86, it's three instructions. 3) A better use of a second register is to hold a two-word hash state. With careful design, no temporaries are needed at all, so it doesn't increase register pressure. And this gets rid of register copying on 2-operand machines, so the code is smaller and faster. 4) Using two words of state weakens the requirement for one-round mixing; we now have two rounds of mixing before cancellation is possible. 5) A two-word hash state also allows operations on both halves to be done in parallel, so on a superscalar processor we get more mixing in fewer cycles. I ended up using a mixing function inspired by the ChaCha and Speck round functions. It is 6 simple instructions and 3 cycles per iteration (assuming multiply by 9 can be done by an "lea" instruction): x ^= *input++; y ^= x; x = ROL(x, K1); x += y; y = ROL(y, K2); y *= 9; Not only is this reversible, two consecutive rounds are reversible: if you are given the initial and final states, but not the intermediate state, it is possible to compute both input words. This means that at least 3 words of input are required to create a collision. (It also has the property, used by hash_name() to avoid a branch, that it hashes all-zero to all-zero.) The rotate constants K1 and K2 were found by experiment. The search took a sample of random initial states (I used 1023) and considered the effect of flipping each of the 64 input bits on each of the 128 output bits two rounds later. Each of the 8192 pairs can be considered a biased coin, and adding up the Shannon entropy of all of them produces a score. The best-scoring shifts also did well in other tests (flipping bits in y, trying 3 or 4 rounds of mixing, flipping all 64*63/2 pairs of input bits), so the choice was made with the additional constraint that the sum of the shifts is odd and not too close to the word size. The final state is then folded into a 32-bit hash value by a less carefully optimized multiply-based scheme. This also has to be fast, as pathname components tend to be short (the most common case is one iteration!), but there's some room for latency, as there is a fair bit of intervening logic before the hash value is used for anything. (Performance verified with "bonnie++ -s 0 -n 1536:-2" on tmpfs. I need a better benchmark; the numbers seem to show a slight dip in performance between 4.6.0 and this patch, but they're too noisy to quote.) Special thanks to Bruce fields for diligent testing which uncovered a nasty fencepost error in an earlier version of this patch. [checkpatch.pl formatting complaints noted and respectfully disagreed with.] Signed-off-by: George Spelvin <linux@sciencehorizons.net> Tested-by: J. Bruce Fields <bfields@redhat.com>
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George Spelvin authored
The "simplified" prime multipliers made very bad hash functions, so get rid of them. This completes the work of 689de1d6. To avoid the inefficiency which was the motivation for the "simplified" multipliers, hash_64() on 32-bit systems is changed to use a different algorithm. It makes two calls to hash_32() instead. drivers/media/usb/dvb-usb-v2/af9015.c uses the old GOLDEN_RATIO_PRIME_32 for some horrible reason, so it inherits a copy of the old definition. Signed-off-by: George Spelvin <linux@sciencehorizons.net> Cc: Antti Palosaari <crope@iki.fi> Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
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George Spelvin authored
That's all that's ever asked for, and it makes the return type of hash_long() consistent. It also allows (upcoming patch) an optimized implementation of hash_64 on 32-bit machines. I tried adding a BUILD_BUG_ON to ensure the number of bits requested was never more than 32 (most callers use a compile-time constant), but adding <linux/bug.h> to <linux/hash.h> breaks the tools/perf compiler unless tools/perf/MANIFEST is updated, and understanding that code base well enough to update it is too much trouble. I did the rest of an allyesconfig build with such a check, and nothing tripped. Signed-off-by: George Spelvin <linux@sciencehorizons.net>
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