The Arm laptop project

Transcript

1. The Arm laptop project
   Johan Hovold
   Hovold Consulting AB
   Kernel Recipes, Paris
   25 September 2023
   

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2. Introduction
   • Windows on Arm (WoA)
   • Laptops built on (Qualcomm) 64-bit Arm SoCs
   • Quiet and power efficient
   • Non-standard boot chain
   • Customised OS
   

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3. Introduction
   • Windows on Arm (WoA)
   • Laptops built on (Qualcomm) 64-bit Arm SoCs
   • Quiet and power efficient
   • Non-standard boot chain
   • Customised OS
   • What would it take to run Linux on them?
   

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4. Project overview
   • Linaro project
   • Funded by Arm and Qualcomm
   • Hardware from Qualcomm and Lenovo
   • Proof-of-concept: Mainline Linux on Arm laptop (built for Windows)
   • How far could we get?
   

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5. People
   • Johan Hovold
   • Bj¨
   orn Andersson
   • Linaro’s Qualcomm landing team
   • Building on work done by Qualcomm, Linaro and many others
   

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6. Talk outline
   • Background
   • Status
   • Work in progress
   • Open issues
   • Setup instructions
   • Distro support
   

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7. Previous work
   • Linaro and Arm collaboration
   • Try to get Linux to boot on WoA laptops
   • ASUS NovaGo TP370QL
   • HP Envy x2
   • Lenovo Mixx 630
   • Lenovo Yoga C630
   • Enable basic features
   • Investigate options for distro support (e.g. ACPI vs DT)
   • https://github.com/aarch64-laptops/
   • #aarch64-laptops on OFTC
   

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8. Lenovo ThinkPad X13s
   • Snapdragon 8xc Gen3 Compute (sc8280xp)
   • 13.3” FHD (1920x1200) display
   • 32 GB LPDDR4 (up to)
   • 1 TB NVMe SSD (up to)
   • Adreno 690 GPU
   • 2 speakers, 2 microphones, headphone jack
   • 5 MP camera
   • Wi-Fi 6E (802.11ax)
   • Bluetooth 5.1
   • 5G modem (optional)
   • 2 x USB-C 3.2 Gen 2
   • 49.5 Wh battery
   

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9. Boot firmware
   • Qualcomm and Windows on Arm
   • UEFI
   • Runtime services not available after boot (e.g. EFI variables)
   • ACPI vs DT
   • Supporting Qualcomm’s non-standard ACPI not feasible
   • DtbLoader.efi
   • Ship devicetree blob with UEFI firmware
   • Allows for generic distro installers
   • Hypervisor
   • UEFI and Linux starts in EL1
   • No virtualisation
   

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10. Work outline
    • Feature implementation and mainlining
    • Reverse engineering
    • Refactoring (technical debt)
    • Firmware requests
    • Bug fixing
    • Patch review
    • Patch tracking
    • Work-in-progress (WIP) branches
    • Support (#aarch64-laptops)
    

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11. WIP branches
    • Important fixes and features under development
    • Minimal johan defconfig
    • Rebased on RC kernels
    • Several regressions found and fixed early
    • Example: IRQ software resend in 6.5-rc1
    • 41 branches so far, latest:
    • https://github.com/jhovold/linux/tree/wip/sc8280xp-v6.6-rc2
    • Announced on #aarch64-laptops
    • Testing by early adopters
    • Repackaged with distro config (e.g. by steev)
    • Base for distro images (e.g. Ubuntu)
    

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12. Device firmware
    • Use Windows firmware files for bringup
    • Work with Lenovo and Qualcomm to get firmware released
    • Wi-Fi board file not compatible with ath11k firmware
    • Took one year to get calibration data released
    • Everything but video acceleration now in linux-firmware.git
    

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13. Mainline feature support
    • 6.0
    • Backlight
    • CPUfreq
    • Keyboard
    • Remoteproc
    • Touchpad
    • Touchscreen
    • USB
    • Watchdog
    • 6.1
    • System suspend
    • 6.2
    • Modem
    • NVMe SSD
    • PCIe (x4)
    • Thermal sensors
    • 6.3
    • Battery
    • External display
    • Internal display (*)
    • 6.4
    • Bluetooth
    • IOMMU (**)
    • RTC
    • Touchpad (alternate)
    • Wi-Fi
    • 6.5
    • Audio
    • GPU
    • USB-C orientation switching
    

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14. Work in progress
    • Camera
    • Raw sensor data
    • Software processing (e.g. debayering)
    • EFI variables1 (merged for 6.7)
    • Maximilian Luz
    • Fingerprint reader1
    • Video acceleration1
    • USB-C muxing (4-lane DisplayPort)
    • Performance optimisation (e.g. better memory bus scaling)
    • Power consumption
    1Supported in WIP branches
    

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15. Power consumption
    • Idle: 3.2 W (15 h)2
    • Suspend: 1.7 W (29 h)
    • Suspend to idle
    • Not yet hitting deepest low-power state
    2Backlight at 66%, PCIe ASPM, Xorg, Wi-Fi
    

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16. Audio
    • Speakers, microphones, headphone jack and DisplayPort working in 6.5
    • Late fix for speaker and headphone distortion
    • Kernel, topology and UCM files need to be updated in lock step
    • Known issues
    • Pops and clicks (partial fix in WIP branch)
    • Microphone distortion
    

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17. GPU
    • Adreno 690 support in Linux 6.5 and Mesa 23.1
    • Rob Clark
    • Important fix in Mesa 23.1.4 (Firefox crash)
    • Extracted a690 GMU firmware not (yet) in linux-firmware
    • Driver will use a660 GMU firmware in 6.6 (and 6.5.3)
    • Use symlink before 6.5.3
    # ln -s a660_gmu.bin a690_gmu.bin
    

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18. Bluetooth
    • Unique device address (BD ADDR) stored externally
    • Need details from Qualcomm (or reverse engineer)
    • No support in bluetoothd for setting custom or random address
    • https://github.com/bluez/bluez/issues/107
    • Must be set manually (or using systemd service) for now
    • Similar problem with Wi-Fi MAC address
    • Falls back to random address
    # btmgmt --index 0 public -addr 00:11:22:33:44:55
    

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19. Remote processors
    • Qualcomm protection-domain mapper daemon (pd-mapper)
    • https://github.com/andersson/pd-mapper
    • Reads configuration shipped with remoteproc firmware
    • Tells remote processors which services to start
    • Tells kernel where to find services
    • Audio
    • Battery
    • USB-C Alternate Mode
    • Battery may not charge if pd-mapper not running
    • Depends on Qualcomm IPC Router name service (qrtr-ns)
    • https://github.com/andersson/qrtr
    • Functionality should be moved to kernel and devicetree
    

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20. Second-source devices
    • X13s comes with one of two touchpad controllers
    • Boot firmware should determine which one is populated
    • Update the devicetree accordingly
    

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21. Touchpad devicetree
    &i2c21 {
    touchpad@15 {
    compatible = "hid -over -i2c";
    reg = <0x15 >;
    interrupts = <182 IRQ_TYPE_LEVEL_LOW >;
    vdd -supply = <&vreg_3p3 >;
    status = "disabled";
    };
    touchpad@2c {
    compatible = "hid -over -i2c";
    reg = <0x2c >;
    interrupts = <182 IRQ_TYPE_LEVEL_LOW >;
    vdd -supply = <&vreg_3p3 >;
    status = "disabled";
    };
    };
    

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22. Touchpad devicetree
    &i2c21 {
    touchpad@15 {
    compatible = "hid -over -i2c";
    reg = <0x15 >;
    interrupts = <182 IRQ_TYPE_LEVEL_LOW >;
    vdd -supply = <&vreg_3p3 >;
    status = "disabled";
    };
    touchpad@2c {
    compatible = "hid -over -i2c";
    reg = <0x2c >;
    interrupts = <182 IRQ_TYPE_LEVEL_LOW >;
    vdd -supply = <&vreg_3p3 >;
    status = "okay";
    };
    };
    

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23. Second-source devices (cont.)
    • X13s firmware does not support this
    • Linux needs to probe both touchpads
    • HID driver already checks if a device is present
    • Used for optionally populated devices (e.g. the X13s touchscreen)
    

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24. HID driver probe
    int i2c_hid_core_probe (struct i2c_client *client , ...)
    {
    ...
    i2c_hid_core_power_up ();
    /* Make sure there is something at this address */
    ret = i2c_smbus_read_byte (client);
    if (ret < 0) {
    i2c_hid_core_power_down ();
    return -ENODEV;
    }
    hid = hid_allocate_device ();
    ...
    hid_add_device (hid);
    return 0;
    }
    

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25. Touchpad devicetree
    &i2c21 {
    touchpad@15 {
    compatible = "hid -over -i2c";
    reg = <0x15 >;
    interrupts = <182 IRQ_TYPE_LEVEL_LOW >;
    vdd -supply = <&vreg_3p3 >;
    status = "okay";
    };
    touchpad@2c {
    compatible = "hid -over -i2c";
    reg = <0x2c >;
    interrupts = <182 IRQ_TYPE_LEVEL_LOW >;
    vdd -supply = <&vreg_3p3 >;
    status = "okay";
    };
    };
    

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26. Asynchronous probe woes
    • Devices can be probed in parallel
    

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27. Asynchronous probe woes
    • Devices can be probed in parallel
    • Interrupt mapping race in IRQ core
    • Affects all shared interrupts
    • Two mappings for the same interrupt line
    • Touchpad interrupts dismissed as spurious
    • Irqdomain locking fixes merged in 6.4
    

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28. Asynchronous probe woes
    • Devices can be probed in parallel
    • Interrupt mapping race in IRQ core
    • Affects all shared interrupts
    • Two mappings for the same interrupt line
    • Touchpad interrupts dismissed as spurious
    • Irqdomain locking fixes merged in 6.4
    • ”Shared” resources claimed temporarily
    • Check existence before acquiring resources
    • Interrupt regression in 6.6-rc1
    • Problem: A reset GPIO can not be shared
    

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29. Asynchronous probe woes
    • Devices can be probed in parallel
    • Interrupt mapping race in IRQ core
    • Affects all shared interrupts
    • Two mappings for the same interrupt line
    • Touchpad interrupts dismissed as spurious
    • Irqdomain locking fixes merged in 6.4
    • ”Shared” resources claimed temporarily
    • Check existence before acquiring resources
    • Interrupt regression in 6.6-rc1
    • Problem: A reset GPIO can not be shared
    • Some resources claimed before HID driver probes
    • Move pin configuration to parent bus node (hack)
    • Or allow sharing?
    

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30. Asynchronous probe woes
    • Devices can be probed in parallel
    • Interrupt mapping race in IRQ core
    • Affects all shared interrupts
    • Two mappings for the same interrupt line
    • Touchpad interrupts dismissed as spurious
    • Irqdomain locking fixes merged in 6.4
    • ”Shared” resources claimed temporarily
    • Check existence before acquiring resources
    • Interrupt regression in 6.6-rc1
    • Problem: A reset GPIO can not be shared
    • Some resources claimed before HID driver probes
    • Move pin configuration to parent bus node (hack)
    • Or allow sharing?
    • Extend devicetree specification?
    • Mark devices as mutually exclusive
    • Force sequential probe
    

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31. Bootloader handover
    • Resources may have been (left) enabled by boot firmware
    • Clocks
    • Regulators
    • Power domains
    • Interconnects
    • Handover should be seamless (e.g. EFI framebuffer)
    • Disable any resources not needed to save power
    

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32. Handover problems
    • Unused clocks and power domains disabled at late init
    • Breaks display handover when display driver built as module
    • Workaround: clk ignore unused and pd ignore unused
    • Ignoring wastes power
    • Fails to disable unused clocks for modular clock drivers
    

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33. Handover problems
    • Unused clocks and power domains disabled at late init
    • Breaks display handover when display driver built as module
    • Workaround: clk ignore unused and pd ignore unused
    • Ignoring wastes power
    • Fails to disable unused clocks for modular clock drivers
    • Unused regulators disabled 30 seconds after late init
    • Breaks early console unless display driver in initramfs
    • Example: Rescue shell or full-disk encryption
    

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34. Handover problems
    • Unused clocks and power domains disabled at late init
    • Breaks display handover when display driver built as module
    • Workaround: clk ignore unused and pd ignore unused
    • Ignoring wastes power
    • Fails to disable unused clocks for modular clock drivers
    • Unused regulators disabled 30 seconds after late init
    • Breaks early console unless display driver in initramfs
    • Example: Rescue shell or full-disk encryption
    • Interconnect state synced when all consumers’ drivers are bound
    • Power state left at maximum if driver fails to probe
    • Example: Firmware missing (video acceleration)
    • Example: Driver disabled
    

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35. Disabling unused resources
    • Need common mechanism for disabling unused resources
    • Could be built on device links and sync-state mechanism, which triggers when all
    consumers’ drivers are bound
    • Also need timer for consumers that fail to probe?
    • Timer extended when a driver is bound (cf. deferred probe)
    • Trigger state sync on expiry
    • Problem: Need to pause timer in rescue shell
    • Alternative: User space triggers sync when booted
    • Use existing state synced sysfs interface?
    

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36. Future work
    • Camera ISP
    • Bluetooth BD ADDR and Wi-Fi MAC address
    • Hibernation
    • Keyboard special keys (e.g. mic mute)
    • Thermal throttling, non-CPU (e.g. GPU, DSP, charger, radio)
    • Trusted Platform Module (TPM)
    • USB Power Delivery (USB-PD)
    • Virtualisation
    

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37. Future work
    • Camera ISP
    • Bluetooth BD ADDR and Wi-Fi MAC address
    • Hibernation
    • Keyboard special keys (e.g. mic mute)
    • Thermal throttling, non-CPU (e.g. GPU, DSP, charger, radio)
    • Trusted Platform Module (TPM)
    • USB Power Delivery (USB-PD)
    • Virtualisation
    

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38. Getting started with X13s
    • Linux 6.5 (mainline or WIP)
    • https://github.com/jhovold/linux/tree/wip/sc8280xp-v6.5
    • make johan defconfig
    • linux-firmware-20230919
    • ln -s a660 gmu.bin a690 gmu.bin
    • qcvss8280.mbn (with WIP branch)
    • alsa-ucm-conf 1.2.10 + volume fixes
    • https://github.com/alsa-project/alsa-ucm-conf/pull/335
    • Mesa 23.1.4
    • Qualcomm pd-mapper and qrtr-ns daemons
    • https://github.com/andersson/pd-mapper
    • https://github.com/andersson/qrtr
    

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39. Kernel command line
    • clk ignore unused (generic issue)
    • pd ignore unused (generic issue)
    • arm64.nopauth (firmware bug)
    • efi=noruntime (firmware bug)
    • iommu.passthrough=0 iommu.strict=0 (USB throughput)
    • pcie aspm.policy=powersupersave (PCIe ASPM)
    

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40. Initramfs
    • Modules needed to boot
    • nvme, phy qcom qmp pcie, pcie qcom
    • Modules needed for early console (optional)
    • i2c hid of, i2c qcom geni
    • leds qcom lpg, pwm bl
    • qrtr, pmic glink altmode, gpio sbu mux, phy qcom qmp combo
    • panel edp, msm, phy qcom edp
    • Depends on config
    • Documented in commit message for johan defconfig
    • Missing display dependency can break EFI framebuffer
    

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41. Distro support
    • https://launchpad.net/~ubuntu-concept/+archive/ubuntu/x13s
    • https://fedoraproject.org/wiki/Thinkpad_X13s
    • https://wiki.debian.org/InstallingDebianOn/Thinkpad/X13s
    

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42. Summary
    • Lenovo ThinkPad X13s well supported by mainline Linux 6.5
    • More features under way (e.g. camera)
    • Working on improving suspend power consumption
    

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43. Wiki
    • For updated status, known issues and other resources, see:
    • https://github.com/jhovold/linux/wiki/X13s
    

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44. Thanks!
    [email protected]
    [email protected]
    

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