- 01 Oct, 2019 23 commits
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Christophe JAILLET authored
At the beginning of the probe function, we have a call to 'request_muxed_region(BRA_SMB_BASE_ADDR, 7, "CEC00001")()' A corresponding 'release_region()' is performed in the remove function but is lacking in the error handling path. Add it. Fixes: b03c2fb9 ("media: add SECO cec driver") Signed-off-by:
Christophe JAILLET <christophe.jaillet@wanadoo.fr> Signed-off-by:
Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by:
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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Hans Verkuil authored
Initialize the context on open() with valid capture and output formats. It is good practice to always have valid formats internally. This solves one vb2 warning in the kernel log where the sizeimage value of the output format was 0 when requesting buffers, which is not allowed. It also simplifies the g_fmt ioctl implementations since they no longer have to check if a valid format was ever set. cedrus_prepare_format() now also validates sizeimage for the output formats, ensuring userspace can't set it to 0 since that would cause the same vb2 warning. Finally remove the sizeimage == 0 check in cedrus_try_fmt_vid_out() since cedrus_prepare_format() will now adjust this value. Signed-off-by:
Jernej Skrabec <jernej.skrabec@siol.net> Signed-off-by:
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Hans Verkuil authored
If an unsupported pixelformat is passed to try_fmt, then pick the first valid pixelformat instead. This is more standard V4L2 behavior. Signed-off-by:
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Hans Verkuil authored
Fixes this compliance warning: $ v4l2-compliance -m0 v4l2-compliance SHA: b514d615166bdc0901a4c71261b87db31e89f464, 32 bits Compliance test for cedrus device /dev/media0: Media Driver Info: Driver name : cedrus Model : cedrus Serial : Bus info : Media version : 5.3.0 Hardware revision: 0x00000000 (0) Driver version : 5.3.0 Required ioctls: warn: v4l2-test-media.cpp(51): empty bus_info test MEDIA_IOC_DEVICE_INFO: OK Signed-off-by: -
Benoit Parrot authored
Switch to SPDX licensing and drop the redundant GPL text. Signed-off-by:
Benoit Parrot <bparrot@ti.com> Acked-by:
Lad Prabhakar <prabhakar.csengg@gmail.com> Signed-off-by:
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Benoit Parrot authored
The bus related static data included in the vpfe_fmt static table can be derived dynamically instead. This simplify the table and it's use. We instead replace the per bus data info with just the usual bit per pixel value for each supported pixel format. Signed-off-by:
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Benoit Parrot authored
The try_fmt was not actually trying out the provided format but merely returning the current format basically like get_fmt. In addition set_fmt should first invoked try_fmt to validate the given format before applying it to the hardware. To fix all of these the whole get/try/set ioctl functions had to be reworked. When calculating the bytesperline/stride and sizeimage format member we don't need to locally store the current value of bytesperpixel as it can easily get derived dynamically. Signed-off-by:
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Benoit Parrot authored
checkpatch.pl nows reports several: WARNING: Prefer using '"%s...", __func__' to using '<function name>', this function's name, in a string. So fix these for the whole driver. At the same time remove the function entry trace log as those can be enabled using ftrace instead. Signed-off-by:
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Benoit Parrot authored
Using a statically defined format array would cause issue when multiple vpfe instance would be connected to sub-device of different capabilities. We need to use an instance based array instead to properly maintain a per port/instance format list. Signed-off-by:
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Benoit Parrot authored
VIDIOC_S_STD should not return an error if the value is identical to the current one. This error was highlighted by the v4l2-compliance test. Signed-off-by:
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Benoit Parrot authored
Returning queued vb2 buffers back to user space is a common task best handled by a helper function. Signed-off-by:
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Benoit Parrot authored
When start_streaming fails the h/w module might be left enabled inadvertently. Make sure it is disabled in the error path. Signed-off-by:
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Benoit Parrot authored
We were originally attempting to stop all processing as soon as possible, but the in-progress DMA operation cannot be canceled. This led to the module being in a busy state and prevented proper power management functionality. The existing implementation would attempt to clean things up by waiting up to 50ms. However when receiving video frame at 15fps or lower, it meant an inter frame arrival rate of 66.6 ms or higher. In such cases upon tear down the following message could be seen: omap_hwmod: vpfe0: _wait_target_disable failed This patch fixes this issue by adding a stopping state where we would wait for the next Vsync before disabling the hardware. Signed-off-by:
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Benoit Parrot authored
Make the ISR code simpler to follow by removing goto and relocating/eliminating duplicate spinlock accesses. Signed-off-by:
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Benoit Parrot authored
Previous generation of this driver were hard coded to handle encoder/decoder where the first line never contains any data and was therefore always skipped, however when dealing with actual camera sensors the first line is always present. Signed-off-by:
Jyri Sarha <jsarha@ti.com> Acked-by:
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Dave Gerlach authored
Currently if vpfe is not active then it returns immediately in the suspend and resume handlers. Change this so that it always performs the pinctrl config so that we can still get proper sleep state configuration on the pins even if we do not need to worry about fully saving and restoring context. Signed-off-by:
Dave Gerlach <d-gerlach@ti.com> Signed-off-by:
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Shuah Khan authored
After practically re-writing the driver to collpase it into a monolith, I am adding myself as a reviewer for vimc driver. Signed-off-by:
Shuah Khan <skhan@linuxfoundation.org> Acked-by:
Helen Koike <helen.koike@collabora.com> Signed-off-by:
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Shuah Khan authored
vimc driver is now a monolithic driver. Update the module parameter usage information to reflect that. [m.chehab+samsung@kernel.org: fix two warnings due to wrontly added spaces] Signed-off-by:
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Shuah Khan authored
Move duplicated IS_SRC and IS_SINK dfines to common header. Rename them to VIMC_IS_SRC and VIM_IS_SINK. Signed-off-by:
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Shuah Khan authored
If vimc module is removed while streaming is in progress, sensor subdev unregister runs into general protection fault when it tries to unregister media entities. This is a common subdev problem related to releasing pads from v4l2_device_unregister_subdev() before calling unregister. Unregister references pads during unregistering subdev. The sd release handler is the right place for releasing all sd resources including pads. The release handlers currently release all resources except the pads. Fix v4l2_device_unregister_subdev() not release pads and release pads from the sd_int_op release handlers. kernel: [ 4136.715839] general protection fault: 0000 [#1] SMP PTI kernel: [ 4136.715847] CPU: 2 PID: 1972 Comm: bash Not tainted 5.3.0-rc2+ #4 kernel: [ 4136.715850] Hardware name: Dell Inc. OptiPlex 790/0HY9JP, BIOS A18 09/24/2013 kernel: [ 4136.715858] RIP: 0010:media_gobj_destroy.part.16+0x1f/0x60 kernel: [ 4136.715863] Code: ff 66 2e 0f 1f 84 00 00 00 00 00 66 66 66 66 90 55 48 89 fe 48 89 e5 53 48 89 fb 48 c7 c7 00 7f cf b0 e8 24 fa ff ff 48 8b 03 <48> 83 80 a0 00 00 00 01 48 8b 43 18 48 8b 53 10 48 89 42 08 48 89 kernel: [ 4136.715866] RSP: 0018:ffff9b2248fe3cb0 EFLAGS: 00010246 kernel: [ 4136.715870] RAX: bcf2bfbfa0d63c2f RBX: ffff88c3eb37e9c0 RCX: 00000000802a0018 kernel: [ 4136.715873] RDX: ffff88c3e4f6a078 RSI: ffff88c3eb37e9c0 RDI: ffffffffb0cf7f00 kernel: [ 4136.715876] RBP: ffff9b2248fe3cb8 R08: 0000000001000002 R09: ffffffffb0492b00 kernel: [ 4136.715879] R10: ffff9b2248fe3c28 R11: 0000000000000001 R12: 0000000000000038 kernel: [ 4136.715881] R13: ffffffffc09a1628 R14: ffff88c3e4f6a028 R15: fffffffffffffff2 kernel: [ 4136.715885] FS: 00007f8389647740(0000) GS:ffff88c465500000(0000) knlGS:0000000000000000 kernel: [ 4136.715888] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 kernel: [ 4136.715891] CR2: 000055d008f80fd8 CR3: 00000001996ec005 CR4: 00000000000606e0 kernel: [ 4136.715894] Call Trace: kernel: [ 4136.715903] media_gobj_destroy+0x14/0x20 kernel: [ 4136.715908] __media_device_unregister_entity+0xb3/0xe0 kernel: [ 4136.715915] media_device_unregister_entity+0x30/0x40 kernel: [ 4136.715920] v4l2_device_unregister_subdev+0xa8/0xe0 kernel: [ 4136.715928] vimc_ent_sd_unregister+0x1e/0x30 [vimc] kernel: [ 4136.715933] vimc_sen_rm+0x16/0x20 [vimc] kernel: [ 4136.715938] vimc_remove+0x3e/0xa0 [vimc] kernel: [ 4136.715945] platform_drv_remove+0x25/0x50 kernel: [ 4136.715951] device_release_driver_internal+0xe0/0x1b0 kernel: [ 4136.715956] device_driver_detach+0x14/0x20 kernel: [ 4136.715960] unbind_store+0xd1/0x130 kernel: [ 4136.715965] drv_attr_store+0x27/0x40 kernel: [ 4136.715971] sysfs_kf_write+0x48/0x60 kernel: [ 4136.715976] kernfs_fop_write+0x128/0x1b0 kernel: [ 4136.715982] __vfs_write+0x1b/0x40 kernel: [ 4136.715987] vfs_write+0xc3/0x1d0 kernel: [ 4136.715993] ksys_write+0xaa/0xe0 kernel: [ 4136.715999] __x64_sys_write+0x1a/0x20 kernel: [ 4136.716005] do_syscall_64+0x5a/0x130 kernel: [ 4136.716010] entry_SYSCALL_64_after_hwframe+0x4 Signed-off-by:
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Shuah Khan authored
vimc uses Component API to split the driver into functional components. The real hardware resembles a monolith structure than component and component structure added a level of complexity making it hard to maintain without adding any real benefit. The sensor is one vimc component that would makes sense to be a separate module to closely align with the real hardware. It would be easier to collapse vimc into single monolithic driver first and then split the sensor off as a separate module. Collapse it into a single monolithic driver removing the Component API. This patch removes the component API and makes minimal changes to the code base preserving the functional division of the code structure. Preserving the functional structure allows us to split the sensor off as a separate module in the future. Major design elements in this change are: - Use existing struct vimc_ent_config and struct vimc_pipeline_config to drive the initialization of the functional components. - Make vimc_device and vimc_ent_config global by moving them to vimc-common.h - Add two new hooks add and rm to initialize and register, unregister and free subdevs. - All component API is now gone and bind and unbind hooks are modified to do "add" and "rm" with minimal changes to just add and rm subdevs. - vimc-core's bind and unbind are now register and unregister. - Add a new field to vimc_device structure for saving the pointers to struct vimc_ent_device(s) subdevs create in their "add" hooks. These get used to create links and removing the subdevs. vimc-core allocates this array which sized to number of entries in the topology defined in the vimc_pipeline_config structure. - vimc-core invokes "add" hooks from its vimc_register_devices(). The "add" hooks remain the same and register subdevs. They don't create platform devices of their own and use vimc's pdev.dev as their reference device. Each "add" hook returns pointer to its struct vimc_ent_device. This is saved in the vimc_device ent_devs array. - vimc-core invokes "rm" hooks from its unregister to unregister subdevs and cleanup. - vimc-core invokes "add" and "rm" hooks with pointer to struct vimc_device and the corresponding vimc_ent_device saved in the ent_devs. The following configure and stream test works on all devices. media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]' media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]' media-ctl -d platform:vimc -V '"Sensor B":0[fmt:SBGGR8_1X8/640x480]' media-ctl -d platform:vimc -V '"Debayer B":0[fmt:SBGGR8_1X8/640x480]' v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=1920,height=1440 v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81 v4l2-ctl -z platform:vimc -d "Raw Capture 1" -v pixelformat=BA81 v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video1 v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video2 v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video3 Signed-off-by:
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zhengbin authored
In media_device_register_entity, if media_graph_walk_init fails, need to free the previously memory. Reported-by:
Hulk Robot <hulkci@huawei.com> Signed-off-by:
zhengbin <zhengbin13@huawei.com> Signed-off-by:
Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by:
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Colin Ian King authored
Don't populate the array init_regs on the stack but instead make it static. Makes the object code smaller by 57 bytes. Before: text data bss dec hex filename 15935 3600 128 19663 4ccf drivers/media/i2c/mt9m001.o After: text data bss dec hex filename 15782 3696 128 19606 4c96 drivers/media/i2c/mt9m001.o (gcc version 9.2.1, amd64) Signed-off-by:
Colin Ian King <colin.king@canonical.com> Signed-off-by:
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- 30 Sep, 2019 17 commits
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Linus Torvalds authored
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git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linuxLinus Torvalds authored
Pull btrfs fixes from David Sterba: "A bunch of fixes that accumulated in recent weeks, mostly material for stable. Summary: - fix for regression from 5.3 that prevents to use balance convert with single profile - qgroup fixes: rescan race, accounting leak with multiple writers, potential leak after io failure recovery - fix for use after free in relocation (reported by KASAN) - other error handling fixups" * tag 'for-5.4-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: btrfs: qgroup: Fix reserved data space leak if we have multiple reserve calls btrfs: qgroup: Fix the wrong target io_tree when freeing reserved data space btrfs: Fix a regression which we can't convert to SINGLE profile btrfs: relocation: fix use-after-free on dead relocation roots Btrfs: fix race setting up and completing qgroup rescan workers Btrfs: fix missing error return if writeback for extent buffer never started btrfs: adjust dirty_metadata_bytes after writeback failure of extent buffer Btrfs: fix selftests failure due to uninitialized i_mode in test inodes -
git://github.com/c-sky/csky-linuxLinus Torvalds authored
Pull csky updates from Guo Ren: "This round of csky subsystem just some fixups: - Fix mb() synchronization problem - Fix dma_alloc_coherent with PAGE_SO attribute - Fix cache_op failed when cross memory ZONEs - Optimize arch_sync_dma_for_cpu/device with dma_inv_range - Fix ioremap function losing - Fix arch_get_unmapped_area() implementation - Fix defer cache flush for 610 - Support kernel non-aligned access - Fix 610 vipt cache flush mechanism - Fix add zero_fp fixup perf backtrace panic - Move static keyword to the front of declaration - Fix csky_pmu.max_period assignment - Use generic free_initrd_mem() - entry: Remove unneeded need_resched() loop" * tag 'csky-for-linus-5.4-rc1' of git://github.com/c-sky/csky-linux: csky: Move static keyword to the front of declaration csky: entry: Remove unneeded need_resched() loop csky: Fixup csky_pmu.max_period assignment csky: Fixup add zero_fp fixup perf backtrace panic csky: Use generic free_initrd_mem() csky: Fixup 610 vipt cache flush mechanism csky: Support kernel non-aligned access csky: Fixup defer cache flush for 610 csky: Fixup arch_get_unmapped_area() implementation csky: Fixup ioremap function losing csky: Optimize arch_sync_dma_for_cpu/device with dma_inv_range csky/dma: Fixup cache_op failed when cross memory ZONEs csky: Fixup dma_alloc_coherent with PAGE_SO attribute csky: Fixup mb() synchronization problem
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git://git.kernel.org/pub/scm/linux/kernel/git/soc/socLinus Torvalds authored
Pull ARM SoC fixes from Olof Johansson: "A few fixes that have trickled in through the merge window: - Video fixes for OMAP due to panel-dpi driver removal - Clock fixes for OMAP that broke no-idle quirks + nfsroot on DRA7 - Fixing arch version on ASpeed ast2500 - Two fixes for reset handling on ARM SCMI" * tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: ARM: aspeed: ast2500 is ARMv6K reset: reset-scmi: add missing handle initialisation firmware: arm_scmi: reset: fix reset_state assignment in scmi_domain_reset bus: ti-sysc: Remove unpaired sysc_clkdm_deny_idle() ARM: dts: logicpd-som-lv: Fix i2c2 and i2c3 Pin mux ARM: dts: am3517-evm: Fix missing video ARM: dts: logicpd-torpedo-baseboard: Fix missing video ARM: omap2plus_defconfig: Fix missing video bus: ti-sysc: Fix handling of invalid clocks bus: ti-sysc: Fix clock handling for no-idle quirks
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git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-traceLinus Torvalds authored
Pull tracing fixes from Steven Rostedt: "A few more tracing fixes: - Fix a buffer overflow by checking nr_args correctly in probes - Fix a warning that is reported by clang - Fix a possible memory leak in error path of filter processing - Fix the selftest that checks for failures, but wasn't failing - Minor clean up on call site output of a memory trace event" * tag 'trace-v5.4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: selftests/ftrace: Fix same probe error test mm, tracing: Print symbol name for call_site in trace events tracing: Have error path in predicate_parse() free its allocated memory tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro tracing/probe: Fix to check the difference of nr_args before adding probe
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git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmcLinus Torvalds authored
Pull more MMC updates from Ulf Hansson: "A couple more updates/fixes for MMC: - sdhci-pci: Add Genesys Logic GL975x support - sdhci-tegra: Recover loss in throughput for DMA - sdhci-of-esdhc: Fix DMA bug" * tag 'mmc-v5.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc: mmc: host: sdhci-pci: Add Genesys Logic GL975x support mmc: tegra: Implement ->set_dma_mask() mmc: sdhci: Let drivers define their DMA mask mmc: sdhci-of-esdhc: set DMA snooping based on DMA coherence mmc: sdhci: improve ADMA error reporting
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Krzysztof Wilczynski authored
Move the static keyword to the front of declaration of csky_pmu_of_device_ids, and resolve the following compiler warning that can be seen when building with warnings enabled (W=1): arch/csky/kernel/perf_event.c:1340:1: warning: ‘static’ is not at beginning of declaration [-Wold-style-declaration] Signed-off-by:
Krzysztof Wilczynski <kw@linux.com> Signed-off-by:
Guo Ren <guoren@kernel.org>
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Valentin Schneider authored
Since the enabling and disabling of IRQs within preempt_schedule_irq() is contained in a need_resched() loop, we don't need the outer arch code loop. Signed-off-by:
Valentin Schneider <valentin.schneider@arm.com> Signed-off-by:
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-miscLinus Torvalds authored
Pull Documentation/process update from Greg KH: "Here are two small Documentation/process/embargoed-hardware-issues.rst file updates that missed my previous char/misc pull request. The first one adds an Intel representative for the process, and the second one cleans up the text a bit more when it comes to how the disclosure rules work, as it was a bit confusing to some companies" * tag 'char-misc-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: Documentation/process: Clarify disclosure rules Documentation/process: Volunteer as the ambassador for Intel
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfsLinus Torvalds authored
Pull more vfs updates from Al Viro: "A couple of misc patches" * 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: afs dynroot: switch to simple_dir_operations fs/handle.c - fix up kerneldoc
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git://git.samba.org/sfrench/cifs-2.6Linus Torvalds authored
Pull more cifs updates from Steve French: "Fixes from the recent SMB3 Test events and Storage Developer Conference (held the last two weeks). Here are nine smb3 patches including an important patch for debugging traces with wireshark, with three patches marked for stable. Additional fixes from last week to better handle some newly discovered reparse points, and a fix the create/mkdir path for setting the mode more atomically (in SMB3 Create security descriptor context), and one for path name processing are still being tested so are not included here" * tag '5.4-rc-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6: CIFS: Fix oplock handling for SMB 2.1+ protocols smb3: missing ACL related flags smb3: pass mode bits into create calls smb3: Add missing reparse tags CIFS: fix max ea value size fs/cifs/sess.c: Remove set but not used variable 'capabilities' fs/cifs/smb2pdu.c: Make SMB2_notify_init static smb3: fix leak in "open on server" perf counter smb3: allow decryption keys to be dumped by admin for debugging
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Mao Han authored
The csky_pmu.max_period has type u64, and BIT() can only return 32 bits unsigned long on C-SKY. The initialization for max_period will be incorrect when count_width is bigger than 32. Use BIT_ULL() Signed-off-by:
Mao Han <han_mao@c-sky.com> Signed-off-by:
Guo Ren <ren_guo@c-sky.com>
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Guo Ren authored
We need set fp zero to let backtrace know the end. The patch fixup perf callchain panic problem, because backtrace didn't know what is the end of fp. Signed-off-by:
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Mike Rapoport authored
The csky implementation of free_initrd_mem() is an open-coded version of free_reserved_area() without poisoning. Remove it and make csky use the generic version of free_initrd_mem(). Signed-off-by:
Mike Rapoport <rppt@linux.ibm.com> Signed-off-by:
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Linus Torvalds authored
Merge active entropy generation updates. This is admittedly partly "for discussion". We need to have a way forward for the boot time deadlocks where user space ends up waiting for more entropy, but no entropy is forthcoming because the system is entirely idle just waiting for something to happen. While this was triggered by what is arguably a user space bug with GDM/gnome-session asking for secure randomness during early boot, when they didn't even need any such truly secure thing, the issue ends up being that our "getrandom()" interface is prone to that kind of confusion, because people don't think very hard about whether they want to block for sufficient amounts of entropy. The approach here-in is to decide to not just passively wait for entropy to happen, but to start actively collecting it if it is missing. This is not necessarily always possible, but if the architecture has a CPU cycle counter, there is a fair amount of noise in the exact timings of reasonably complex loads. We may end up tweaking the load and the entropy estimates, but this should be at least a reasonable starting point. As part of this, we also revert the revert of the ext4 IO pattern improvement that ended up triggering the reported lack of external entropy. * getrandom() active entropy waiting: Revert "Revert "ext4: make __ext4_get_inode_loc plug"" random: try to actively add entropy rather than passively wait for it
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Linus Torvalds authored
This reverts commit 72dbcf72. Instead of waiting forever for entropy that may just not happen, we now try to actively generate entropy when required, and are thus hopefully avoiding the problem that caused the nice ext4 IO pattern fix to be reverted. So revert the revert. Cc: Ahmed S. Darwish <darwish.07@gmail.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Willy Tarreau <w@1wt.eu> Cc: Alexander E. Patrakov <patrakov@gmail.com> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds authored
For 5.3 we had to revert a nice ext4 IO pattern improvement, because it caused a bootup regression due to lack of entropy at bootup together with arguably broken user space that was asking for secure random numbers when it really didn't need to. See commit 72dbcf72 (Revert "ext4: make __ext4_get_inode_loc plug"). This aims to solve the issue by actively generating entropy noise using the CPU cycle counter when waiting for the random number generator to initialize. This only works when you have a high-frequency time stamp counter available, but that's the case on all modern x86 CPU's, and on most other modern CPU's too. What we do is to generate jitter entropy from the CPU cycle counter under a somewhat complex load: calling the scheduler while also guaranteeing a certain amount of timing noise by also triggering a timer. I'm sure we can tweak this, and that people will want to look at other alternatives, but there's been a number of papers written on jitter entropy, and this should really be fairly conservative by crediting one bit of entropy for every timer-induced jump in the cycle counter. Not because the timer itself would be all that unpredictable, but because the interaction between the timer and the loop is going to be. Even if (and perhaps particularly if) the timer actually happens on another CPU, the cacheline interaction between the loop that reads the cycle counter and the timer itself firing is going to add perturbations to the cycle counter values that get mixed into the entropy pool. As Thomas pointed out, with a modern out-of-order CPU, even quite simple loops show a fair amount of hard-to-predict timing variability even in the absense of external interrupts. But this tries to take that further by actually having a fairly complex interaction. This is not going to solve the entropy issue for architectures that have no CPU cycle counter, but it's not clear how (and if) that is solvable, and the hardware in question is largely starting to be irrelevant. And by doing this we can at least avoid some of the even more contentious approaches (like making the entropy waiting time out in order to avoid the possibly unbounded waiting). Cc: Ahmed Darwish <darwish.07@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Nicholas Mc Guire <hofrat@opentech.at> Cc: Andy Lutomirski <luto@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Willy Tarreau <w@1wt.eu> Cc: Alexander E. Patrakov <patrakov@gmail.com> Cc: Lennart Poettering <mzxreary@0pointer.de> Signed-off-by:
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