| Age | Commit message (Collapse) | Author | Files | Lines |
|---|
|
When unbinding a process from a device (initiated by amd_iommu_v2), the
driver needs to make sure that process still exists in the process table.
There is a possibility that amdkfd's own notifier handler -
kfd_process_notifier_release() - was called before the unbind function
and it already removed the process from the process table.
v2:
Because there can be only one process with the specified pasid, and
because *p can't be NULL inside the hash_for_each_rcu macro, it is more
reasonable to just put the whole code inside the if statement that
compares the pasid value. That way, when we exit hash_for_each_rcu, we
simply exit the function as well.
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
CC: Stable <stable@vger.kernel.org>
|
|
Signed-off-by: Dave Airlie <airlied@redhat.com>
|
|
drm_fb_cma code has a nice helper function to display in the debugfs
information about the underlying framebuffers used by HDLCD:
$ cat /sys/kernel/debug/dri/0/fb
fb: 1920x1200@XR24
0: offset=0 pitch=7680, obj: 0 ( 2) 001011ba 0x00000000fc300000 ffffff800a27c000 9338880
fb: 1920x1200@XR24
0: offset=0 pitch=7680, obj: 0 ( 2) 001008ca 0x00000000fba00000 ffffff8009987000 9338880
fb: 1920x1200@XR24
0: offset=0 pitch=7680, obj: 0 ( 1) 00100000 0x00000000fb100000 ffffff8008fdc000 9216000
Add the entry in HDLCD's debugfs node.
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
|
|
Harden the plane_check() code to drop attempts at scaling because
that is not supported. Make hdlcd_plane_atomic_update() set the pitch
and line length registers that correctly reflect the plane's values.
And make hdlcd_crtc_mode_set_nofb() a helper function for
hdlcd_crtc_enable() rather than an exposed hook.
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
|
|
event_list just reimplemented what drm_crtc_arm_vblank_event does. And
we also need to send out drm events when shutting down a pipe.
With this it's possible to use the new nonblocking commit support in
the helpers.
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
|
|
Because the HDLCD driver acts as a component master it can end
up enabling the runtime PM functionality before the encoders
are initialised. This can cause crashes if the component slave
never probes (missing module) or if the PM operations kick in
before the probe finishes.
Move the enabling of the runtime PM after the component master
has finished collecting the slave components and use the DRM
atomic helpers to suspend and resume the device.
Tested-by: Robin Murphy <Robin.Murphy@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
|
|
Connectors are unregistered by mtk_drm_drv via drm_connector_unregister_all().
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
Do not try to dereference dpi if it is NULL.
Since dpi can never be NULL when mtk_dpi_set_display_mode() is called,
remove the message.
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
If kmalloc() returned NULL we would end up dereferencing "state" a
couple lines later.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
|
|
Reset crtc->state to NULL after freeing the state object and call
__drm_atomic_helper_crtc_destroy_state() helper instead of manually
calling drm_property_unreference_blob().
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
|
|
- Fixed black screen for some resolutions of G200e rev4
- Fixed testm & testn which had predetermined value.
Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Mathieu Larouche <mathieu.larouche@matrox.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
|
|
Since the introduction of (struct_mutex) lockless GEM bo freeing, there
are a pair of driver vfuncs for freeing the GEM bo, of which the driver
may choose to only implement driver->gem_object_free_unlocked (and so
avoid taking the struct_mutex along the free path). However, the CMA GEM
helpers were still calling driver->gem_free_object directly, now NULL,
and promptly dying on the fancy new lockless drivers. Oops.
Robert Foss bisected this to b82caafcf2303 (drm/vc4: Use lockless gem BO
free callback) on his vc4 device, but that just serves as an enabler for
9f0ba539d13ae (drm/gem: support BO freeing without dev->struct_mutex).
Reported-by: Robert Foss <robert.foss@collabora.com>
Fixes: 9f0ba539d13ae (drm/gem: support BO freeing without dev->struct_mutex)
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Robert Foss <robert.foss@collabora.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: stable@vger.kernel.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Robert Foss <robert.foss@collabora.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
|
|
After commit 027b3f8ba9277410c3191d72d1ed2c6146d8a668 ("drm/modes: stop
handling framebuffer special") extra fb refs are left around when doing
atomic modesetting.
The problem is that the new drm_property_change_valid_get() does not
return anything in the '**ref' parameter, which causes
drm_property_change_valid_put() to do nothing.
For some reason this doesn't cause problems with legacy API.
Also, previously the code only set the 'ref' variable for fbs, with this
patch the 'ref' is set for all objects.
Fixes: 027b3f8ba927 ("drm/modes: stop handling framebuffer special")
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
|
|
drm_atomic_set_mode_prop_for_crtc() does not clear the state->mode, so
old data may be left there when a new mode is set, possibly causing odd
issues.
This patch improves the situation by always clearing the state->mode
first.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: stable@vger.kernel.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
|
|
Commit 652353e6e561c2aeeac62df183f721f6f9b5b45f ("drm/sti: set CRTC
modesetting parameters") added a hack to avoid warnings related to
setting mode with atomic API. With the previous patch, the hack should
no longer be necessary.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
|
|
When setting mode via MODE_ID property,
drm_atomic_set_mode_prop_for_crtc() does not call
drm_mode_set_crtcinfo() which possibly causes:
"[drm:drm_calc_timestamping_constants [drm]] *ERROR* crtc 32: Can't
calculate constants, dotclock = 0!"
Whether the error is seen depends on the previous data in state->mode,
as state->mode is not cleared when setting new mode.
This patch adds drm_mode_set_crtcinfo() call to
drm_mode_convert_umode(), which is called in both legacy and atomic
paths. This should be fine as there's no reason to call
drm_mode_convert_umode() without also setting the crtc related fields.
drm_mode_set_crtcinfo() is removed from the legacy drm_mode_setcrtc() as
that is no longer needed.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
|
|
A lot of the display drivers for OMAP use the gpio descriptor functions
that are only available in linux/gpio.h if GPIOLIB is enabled and
otherwise produce a build error:
drivers/gpu/drm/omapdrm/displays/encoder-opa362.c: In function 'opa362_enable':
drivers/gpu/drm/omapdrm/displays/encoder-opa362.c:101:3: error: implicit declaration of function 'gpiod_set_value_cansleep' [-Werror=implicit-function-declaration]
drivers/gpu/drm/omapdrm/displays/panel-dpi.c: In function 'panel_dpi_probe_pdata':
drivers/gpu/drm/omapdrm/displays/panel-dpi.c:189:23: error: implicit declaration of function 'gpio_to_desc' [-Werror=implicit-function-declaration]
drivers/gpu/drm/omapdrm/displays/panel-sharp-ls037v7dw01.c: In function 'sharp_ls_enable':
drivers/gpu/drm/omapdrm/displays/panel-sharp-ls037v7dw01.c:120:3: error: implicit declaration of function 'gpiod_set_value_cansleep' [-Werror=implicit-function-declaration]
This replaces the existing linux/gpio.h with linux/gpio/consumer.h
where needed. In case of panel-lgphilips-lb035q02.c however, we
also have to include linux/gpio.h to get the definition of gpio_is_valid
and gpio_set_value_cansleep that are used for the non-DT case.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[tomi.valkeinen@ti.com: resolved conflicts]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
|
|
The omapdrm driver relies on this header to be included
implicitly, but this does not always work, and I get
this error in randconfig builds:
gpu/drm/omapdrm/dss/hdmi_phy.c: In function 'hdmi_phy_dump':
gpu/drm/omapdrm/dss/hdmi_phy.c:34:2: error: implicit declaration of function 'seq_printf' [-Werror=implicit-function-declaration]
gpu/drm/omapdrm/dss/hdmi_wp.c: In function 'hdmi_wp_dump':
gpu/drm/omapdrm/dss/hdmi_wp.c:26:2: error: implicit declaration of function 'seq_printf' [-Werror=implicit-function-declaration]
gpu/drm/omapdrm/dss/hdmi_pll.c: In function 'hdmi_pll_dump':
gpu/drm/omapdrm/dss/hdmi_pll.c:30:2: error: implicit declaration of function 'seq_printf' [-Werror=implicit-function-declaration]
This adds the #include statements in all files that have
a seq_printf statement.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
|
|
This reverts commit 1c278e5e3718d15475ec08ee2135f37a6b13361c.
If DRM_OMAP does not select OMAP2_DSS it is possible to build a kernel with
DRM_OMAP only and not selecting OMAP2_DSS. Since omapdrm depends on
OMAP2_DSS this will result on broken kernel build.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
|
|
regulator_can_change_voltage() is deprecated and it's use is not necessary
as commit:
6a0028b3dd67b regulator: Deprecate regulator_can_change_voltage()
describers it clearly.
Also, regulator_set_voltage() is misused in the driver, as it is
supposed to be used only in cases where the regulator voltage needs to
be changed dynamically at runtime. In DSS's case, we always want a fixed
voltage, set in the .dts files.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
|
|
The DDC scl high and low times were set to the minimum values
from the i2c specification, but the i2c specification takes into
account the rise time and fall time to calculate the frequency.
To pass HDMI certification DDC can not exceed 100kHz therefore in
a system where the rise times and fall times are negligible the high
and low times for scl need to be 10us.
Signed-off-by: Jim Lodes <jim.lodes@garmin.com>
Signed-off-by: J.D. Schroeder <jay.schroeder@garmin.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
|
|
The AVI infoframe R0-R3 in the 2nd data byte represents the
Active Format Aspect Ratio. It is four bits long not two bits.
This fixes that mask used to extract the bits before writing the
bits to the hardware registers.
Signed-off-by: Jim Lodes <jim.lodes@garmin.com>
Signed-off-by: J.D. Schroeder <jay.schroeder@garmin.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
|
|
hdmi_core_powerdown_disable() is supposed to disable HDMI core's
power-down mode. However, the function sets the power-down bit to 0,
which means "enable power-down".
This hasn't caused any issues as the PD seems to affect only interrupts
from HDMI core, and none of those interrupts are used at the moment. CEC
functionality requires core interrupts, and the PD mode needs to be
fixed.
This patch fixes hdmi_core_powerdown_disable() to actually disable the
PD mode.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
|
|
With certain kernel config options many omapdrm files fail to compile
due to missing include of linux/gpio/consumer.h and linux/of.h.
This patch adds those includes.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reported-by: Dan Murphy <dmurphy@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
|
|
In some configurations, we can build the OMAP dss driver without
implictly including the pinctrl consumer definitions, causing
a build error:
gpu/drm/omapdrm/dss/dss.c: In function 'dss_runtime_suspend':
gpu/drm/omapdrm/dss/dss.c:1268:2: error: implicit declaration of function 'pinctrl_pm_select_sleep_state' [-Werror=implicit-function-declaration]
This adds an explicit #include.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
|
|
Since the drm core sets plane->crtc correctly, we don't need to do that.
Signed-off-by: Liu Ying <gnuiyl@gmail.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
Signed-off-by: Liu Ying <gnuiyl@gmail.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
This patch allows to select a specific video mode from a list of modes
defined in DT by setting the 'native-mode' property appropriately.
This change does not affect the behaviour of existing platforms, since
they either:
- have just one display-timings subnode
- have the native-mode property pointing to the first entry
- let the bootloader select the appropriate timing
Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
The 'mode_valid' flag is never set in this driver. Remove it and the
code that depends on it.
Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
This patch allows panels to set pixel clock and data enable pin polarity
other than the default of driving data at the falling pixel clock edge
and active high display enable.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
Advertise the DRM_FORMAT_UYVY and DRM_FORMAT_VYUY formats to userspace.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
Instead of using of_graph_get_port_by_id() to get the port and then
of_get_child_by_name() to get the first endpoint, get to the endpoint
in a single step.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
Instead of using of_graph_get_port_by_id() to get the port and then
of_get_child_by_name() to get the first endpoint, get to the endpoint
in a single step.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
Document the ddc-i2c-bus property used by imx-ldb driver to read EDID
information via I2C interface.
Signed-off-by: Akshay Bhat <akshay.bhat@timesys.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
Add support for reading EDID over Display Data Channel. If no DDC
adapter is available, falls back to hardcoded EDID or display-timings
node as before.
Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Akshay Bhat <akshay.bhat@timesys.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|
|
|
|
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: fcfd2fbf22d2 ("fs/namei.c: Add hashlen_string() function")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
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: fcfd2fbf22d2 ("fs/namei.c: Add hashlen_string() function")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
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>
|
|
Commit c8f33d0bec99 ("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: c8f33d0bec99 ("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>
|
|
Commit ce657611baf9 ("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: ce657611baf9 ("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>
|
|
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: 5d22fc25d4fc ("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>
|
|
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
|
|
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>
|
|
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.html
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
|
|
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
|
|
Patch 0fed3ac866 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>
|
|
The "simplified" prime multipliers made very bad hash functions, so get rid
of them. This completes the work of 689de1d6ca.
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>
|
|
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>
|
|
Finally, the first use of previous two patches: eliminate the
separate ad-hoc string hash functions in the sunrpc code.
Now hash_str() is a wrapper around hash_string(), and hash_mem() is
likewise a wrapper around full_name_hash().
Note that sunrpc code *does* call hash_mem() with a zero length, which
is why the previous patch needed to handle that in full_name_hash().
(Thanks, Bruce, for finding that!)
This also eliminates the only caller of hash_long which asks for
more than 32 bits of output.
The comment about the quality of hashlen_string() and full_name_hash()
is jumping the gun by a few patches; they aren't very impressive now,
but will be improved greatly later in the series.
Signed-off-by: George Spelvin <linux@sciencehorizons.net>
Tested-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: linux-nfs@vger.kernel.org
|
Oded Gabbay
Dave Airlie
Liviu Dudau
Daniel Vetter
Philipp Zabel
Dan Carpenter
Boris Brezillon
Mathieu Larouche
Chris Wilson
Tomi Valkeinen
Arnd Bergmann
Peter Ujfalusi
Jim Lodes
Liu Ying
Lothar Waßmann
Akshay Bhat
Steve Longerbeam
Linus Torvalds
George Spelvin
Mikulas Patocka
Guenter Roeck