Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst
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ax_spi_fill_tx_fifo() can be called from ax_spi_irq() which is a hard
irq handler. Replace usleep_range(10, 10) with udelay(10) in atomic
context.
Fixes: e75a6b00ad79 ("spi: axiado: Add driver for Axiado SPI DB controller")
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
Link: https://patch.msgid.link/20260428-axiado-v1-1-cd767500af72@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Two CTRLR0 macros are defined but never referenced, and both are wrong:
- CR0_XFM_MASK shifts by SPI_XFM_OFFSET, which does not exist anywhere
in the tree. The intended symbol is CR0_XFM_OFFSET.
- CR0_MTM_OFFSET is defined as 0x21, i.e. bit 33 of a 32-bit register.
The value is meaningless and the macro is unused.
Drop both. They can be re-introduced correctly when an actual user
appears.
Signed-off-by: John Madieu <john.madieu@gmail.com>
Link: https://patch.msgid.link/20260425092936.2590132-3-john.madieu@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
rockchip_spi_isr() decides whether the current interrupt was the
cs-inactive event by reading IMR:
if (rs->cs_inactive &&
readl_relaxed(rs->regs + ROCKCHIP_SPI_IMR) & INT_CS_INACTIVE)
ctlr->target_abort(ctlr);
IMR is the interrupt mask register: it tells which sources are enabled,
not which one fired. In the PIO path, rockchip_spi_prepare_irq() enables
both INT_RF_FULL and INT_CS_INACTIVE in IMR when rs->cs_inactive is true:
if (rs->cs_inactive)
writel_relaxed(INT_RF_FULL | INT_CS_INACTIVE,
rs->regs + ROCKCHIP_SPI_IMR);
so the IMR check is always true once cs_inactive is enabled, and every
PIO interrupt - including normal RF_FULL completions - is dispatched to
ctlr->target_abort(), aborting the transfer. The bug is reachable on
ROCKCHIP_SPI_VER2_TYPE2 in target mode with a DMA-capable controller
when the transfer is short enough to fall back to PIO
(rockchip_spi_can_dma() returns false below fifo_len).
Read ISR (which is RISR masked by IMR) so the check actually reflects
which interrupt fired, and parenthesise the expression for clarity while
at it.
Fixes: 869f2c94db92 ("spi: rockchip: Stop spi slave dma receiver when cs inactive")
Signed-off-by: John Madieu <john.madieu@gmail.com>
Link: https://patch.msgid.link/20260425092936.2590132-2-john.madieu@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
rzv2h_rspi_setup_clock() is declared to return u32 but returns -EINVAL
when no valid clock parameters are found. Cast to u32, -EINVAL becomes
0xffffffea, which is a non-zero value. The caller in
rzv2h_rspi_prepare_message() guards against failure with:
rspi->freq = rzv2h_rspi_setup_clock(rspi, speed_hz);
if (!rspi->freq)
return -EINVAL;
Because 0xffffffea is non-zero, the check is bypassed and the controller
proceeds to program SPBR/SPCMD with stale values, leading to an unknown
bit rate.
Return 0 on the failed-search path, consistent with the existing
clk_set_rate() failure path which already returns 0.
Fixes: 77d931584dd3 ("spi: rzv2h-rspi: make transfer clock rate finding chip-specific")
Signed-off-by: John Madieu <john.madieu.xa@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Link: https://patch.msgid.link/20260425024725.2393632-1-john.madieu.xa@bp.renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Pull clk fix from Stephen Boyd:
"One more fix for the merge window to avoid a boot hang on
Raspberry Pi 3B by marking the VEC clk critical so that it
doesn't get turned off and hang the bus"
* tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
clk: bcm: rpi: Mark VEC clock as CLK_IGNORE_UNUSED
Pull PCIe TSP update from Dan Williams:
"A small update for the TSM core. It is arguably a fix and coming in
late as I have been offline the past few weeks:
- Drop class_create() for the 'tsm' class"
* tag 'tsm-for-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/devsec/tsm:
virt: coco: change tsm_class to a const struct
On Raspberry Pi 3B, the VEC clock is used by the VideoCore firmware
display driver, which remains active until the vc4 driver loads and
sends NOTIFY_DISPLAY_DONE. If this clock is disabled during boot, a bus
lockup happens and the firmware becomes unresponsive, causing a complete
system lockup.
Mark the VEC clock with CLK_IGNORE_UNUSED so it survives the unused
clock disablement and remains available until the vc4 driver takes over
display management.
Fixes: 672299736af6 ("clk: bcm: rpi: Manage clock rate in prepare/unprepare callbacks")
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/r/5f0bec08-f458-4fba-8bf3-06817a100c4c@sirena.org.uk
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patch.msgid.link/20260401111416.562279-2-mcanal@igalia.com
Tested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Brian Masney <bmasney@redhat.com> # Active contributor to clk
Reviewed-by: Stefan Wahren <wahrenst@gmx.net>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Pull Kbuild fixes from Nicolas Schier:
- builddeb - avoid recompiles for non-cross-compiles
Avoid triggering complete rebuilds for non-cross-compile Debian
package builds by only triggering the rebuild of host tools for
actual cross-compile builds
- Never respect CONFIG_WERROR / W=e to fixdep
Avoid spurious rebuilds of fixdep w/ and w/o -Werror during a single
kbuild invocation by never respecting CONFIG_WERROR for fixdep
* tag 'kbuild-fixes-7.1-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux:
kbuild: Never respect CONFIG_WERROR / W=e to fixdep
kbuild: builddeb - avoid recompiles for non-cross-compiles
The class_create() call has been deprecated in favor of class_register()
as the driver core now allows for a struct class to be in read-only
memory. Change tsm_class to be a const struct class and drop the
class_create() call. Compile tested only.
Link: https://lore.kernel.org/all/2023040244-duffel-pushpin-f738@gregkh/
Changes with v1:
- Removed redundant int err variable.
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/20260306183325.245254-1-jkoolstra@xs4all.nl
Signed-off-by: Dan Williams <djbw@kernel.org>
* clk-samsung:
clk: samsung: exynos850: Add APM-to-AP mailbox clock
dt-bindings: clock: exynos850: Add APM_AP MAILBOX clock
clk: samsung: Use %pe format to simplify
clk: samsung: pll: Fix possible truncation in a9fraco recalc rate
clk: samsung: exynosautov920: add block G3D clock support
dt-bindings: clock: exynosautov920: add G3D clock definitions
clk: samsung: gs101: harmonise symbol names (clock arrays)
clk: samsung: artpec-9: Add initial clock support for ARTPEC-9 SoC
clk: samsung: Add clock PLL support for ARTPEC-9 SoC
dt-bindings: clock: Add ARTPEC-9 clock controller
* clk-qcom: (67 commits)
clk: qcom: gcc: Add multiple global clock controller driver for Nord SoC
clk: qcom: rpmh: Add support for Nord rpmh clocks
clk: qcom: Add TCSR clock driver for Nord SoC
dt-bindings: clock: qcom: Add Nord Global Clock Controller
dt-bindings: clock: qcom-rpmhcc: Add support for Nord SoCs
dt-bindings: clock: qcom: Document the Nord SoC TCSR Clock Controller
clk: qcom: gcc-x1e80100: Keep GCC USB QTB clock always ON
clk: qcom: Constify list of critical CBCR registers
clk: qcom: Constify qcom_cc_driver_data
clk: qcom: videocc-glymur: Constify qcom_cc_desc
clk: qcom: Add a driver for SM8750 GPU clocks
dt-bindings: clock: qcom: Add SM8750 GPU clocks
clk: qcom: ipq-cmn-pll: Add IPQ8074 SoC support
dt-bindings: clock: qcom: Add CMN PLL support for IPQ8074
clk: qcom: ipq-cmn-pll: Add IPQ6018 SoC support
dt-bindings: clock: qcom: Add CMN PLL support for IPQ6018
clk: qcom: gdsc: Fix error path on registration of multiple pm subdomains
dt-bindings: clock: qcom: Add missing power-domains property
clk: qcom: gcc-eliza: Enable FORCE_MEM_CORE_ON for UFS AXI PHY clock
clk: qcom: dispcc-sc7180: Add missing MDSS resets
...
* clk-round:
clk: divider: remove divider_round_rate() and divider_round_rate_parent()
clk: divider: remove divider_ro_round_rate_parent()
clk: remove round_rate() clk ops
clk: composite: convert from round_rate() to determine_rate()
clk: test: remove references to clk_ops.round_rate
* clk-sai:
clk: fsl-sai: Add MCLK generation support
clk: fsl-sai: Extract clock setup into fsl_sai_clk_register()
dt-bindings: clock: fsl-sai: Document clock-cells = <1> support
clk: fsl-sai: Add i.MX8M support with 8 byte register offset
clk: fsl-sai: Sort the headers
dt-bindings: clock: fsl-sai: Document i.MX8M support
* clk-cleanup:
clk: visconti: pll: initialize clk_init_data to zero
clk: xgene: Fix mapping leak in xgene_pllclk_init()
clk: Simplify clk_is_match()
clk: baikal-t1: Remove not-going-to-be-supported code for Baikal SoC
clk: mvebu: armada-37xx-periph: fix __iomem casts in structure init
clk: qoriq: avoid format string warning
Pull power utility updates from Len Brown:
"x86_energy_perf_policy:
- Initial SoC Slider support
turbostat:
- Display HT siblings in cpu# order
- Add Module-ID column
- Print Core-ID and APIC-ID in hex
- Fix misc bugs"
* tag 'power-utilities-2026.04.25' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux:
tools/power x86_energy_perf_policy: Version 2026.04.25
tools/power x86_energy_perf_policy.8: Document SoC Slider Options
tools/power x86_energy_perf_policy: Enhances SoC Slider related checks
tools/power turbostat: v2026.04.21
tools/power turbostat: Process HT siblings in CPU order
tools/power turbostat: Show module_id column
tools/power turbostat: Print core_id and apic_id in hex
tools/power turbostat: Cleanup print helper functions
tools/power turbostat: Fix --cpu-set 1 regression on HT systems
tools/power turbostat: Fix --cpu-set 0 regression on HT systems
tools/power turbostat: Fix unrecognized option '-P'
tools/power turbostat: Fix AMD RAPL regression on big systems
tools/power/x86: Add SOC slider and platform profile support
The fixdep hostprog may be built multiple times during a single build.
Once during the configuration phase and later during the regular phase.
As only the regular build phase respects CONFIG_WERROR / W=e, the
compiler flags might change between the phases, leading to rebuilds.
Example, the rebuilds will happen twice on each invocation of the build:
$ make allyesconfig prepare
make[1]: Entering directory '/tmp/deleteme'
HOSTCC scripts/basic/fixdep
#
# No change to .config
#
HOSTCC scripts/basic/fixdep
DESCEND objtool
INSTALL libsubcmd_headers
make[1]: Leaving directory '/tmp/deleteme'
Fix the compilation flags used for scripts/basic/ before
scripts/Makefile.warn is evaluated to stop CONFIG_WERROR / W=e
influencing the fixdep build to avoid the spurious rebuilds.
Fixes: 7ded7d37e5f5 ("scripts/Makefile.extrawarn: Respect CONFIG_WERROR / W=e for hostprogs")
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260422-kbuild-scripts-basic-werror-v1-1-8c6912ff22e0@weissschuh.net
Signed-off-by: Nicolas Schier <nsc@kernel.org>
* clk-tenstorrent:
clk: tenstorrent: Add Atlantis clock controller driver
reset: tenstorrent: Add reset controller for Atlantis
dt-bindings: clk: tenstorrent: Add tenstorrent,atlantis-prcm-rcpu
* clk-rockchip:
clk: rockchip: rk3568: Add PCIe pipe clock gates
clk: rockchip: Add clock controller for the RV1103B
dt-bindings: clock: rockchip: Add RV1103B CRU support
* clk-imx:
clk: imx8mq: Correct the CSI PHY sels
clk: vf610: Add support for the Ethernet switch clocks
dt-bindings: clock: vf610: Add definitions for MTIP L2 switch
dt-bindings: clock: vf610: Drop VF610_CLK_END define
clk: vf610: Move VF610_CLK_END define to clk-vf610 driver
clk: imx: imx8-acm: fix flags for acm clocks
clk: imx: imx6q: Fix device node reference leak in of_assigned_ldb_sels()
clk: imx: imx6q: Fix device node reference leak in pll6_bypassed()
clk: imx: fracn-gppll: Add 477.4MHz support
clk: imx: fracn-gppll: Add 333.333333 MHz support
clk: imx: pll14xx: Use unsigned format specifier
dt-bindings: clock: imx6q[ul]-clock: add optional clock enet[1]_ref_pad
* clk-allwinner:
clk: sunxi-ng: sun55i-a523-r: Add missing r-spi module clock
Pull Samsung SoC clock driver updates from Krzysztof Kozlowski:
- Axis ARTPEC-9: Add new PLL clocks and new drivers for eight clock
controllers on the SoC
- ExynosAutov920: Add G3D (GPU) clock controller
- Exynos850: Define missing clock for the APM mailbox
* tag 'samsung-clk-7.1' of https://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux:
clk: samsung: exynos850: Add APM-to-AP mailbox clock
dt-bindings: clock: exynos850: Add APM_AP MAILBOX clock
clk: samsung: Use %pe format to simplify
clk: samsung: pll: Fix possible truncation in a9fraco recalc rate
clk: samsung: exynosautov920: add block G3D clock support
dt-bindings: clock: exynosautov920: add G3D clock definitions
clk: samsung: gs101: harmonise symbol names (clock arrays)
clk: samsung: artpec-9: Add initial clock support for ARTPEC-9 SoC
clk: samsung: Add clock PLL support for ARTPEC-9 SoC
dt-bindings: clock: Add ARTPEC-9 clock controller
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