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Linux Kernel developer and maintainer
🇵🇱 🇪🇺 🇰🇷 🇮🇱 🇺🇦 🇨🇭
IRC: krzk
Kernel work related account. Other accounts of mine: @krzk@mastodon.social

Krzysztof Kozlowski

Edited 3 days ago
Since a year we got some contributions for converting Devicetree bindings from TXT to DT schema as part of some sort mentorship programs. This is great although leads to some misunderstandings in that work, considering mentorships did not ask DT maintainers about some sort of guidance. To clarify:

1. Please convert bindings which have active DTS users. First choose bindings with DTS built by arm64 defconfig, then next choice by arm multi_v7 defconfig. Then any other ARM or different architecture DTS.

2. Be sure dt_bindings_check (including yamllint) and checkpatch pass without any warnings. See writing-schema.rst document.

3. Be sure DTS using this binding passes dtbs_check validation. If this means binding needs to be adapted during conversion, mention briefly in commit message changes done comparing to pure TXT->DT schema conversion. Sometimes DTS has to be fixed. Sometimes both - DTS and binding - must be changed, because actual ABI (Linux drivers) is different.
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Krzysztof Kozlowski

That's an interesting session: @cas explaining current status of upstream U-Boot on Qualcomm robotic platforms - using mainline kernel DTS and getting to SystemReady IR.
Slides: https://calebs.dev/u-boot24.pdf
https://www.kitefor.events/events/linaro-connect-24/submissions/183
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Krzysztof Kozlowski

Edited 12 days ago
@abelvesa explaining the hacking setup used during his bringing up of the Qualcomm X Elite compute platform in Linaro:
https://www.kitefor.events/events/linaro-connect-24/submissions/182
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Krzysztof Kozlowski

Just a reminder: only a week to hear me babbling about Linux kernel DTS validation and shared reset GPIOs on Embedded Open Source Summit/OSSNA 2024. Don't miss it and come to say hi!
EOSS: https://sched.co/1aBEf
OSSNA: https://sched.co/1aPvr
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Krzysztof Kozlowski

Edited 2 months ago

Hey, Google, not again! How am I supposed to send my patches?

smtplib.SMTPDataError: 5.4.5 Daily user sending limit exceeded.

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Krzysztof Kozlowski

Preparing speeches for conferences was always rather difficult for me. Went slow, somehow painful. But now I have wonderful data, which I am going to present, and it is just pleasure to write the slides slowly reaching the conclusion I want to share!
https://sched.co/1aBEf
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Vlastimil Babka

Thanks Pope for making me angry enough! Don't like your fundraising campaign style, but it worked! #DronesNotWhiteFlags
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Krzysztof Kozlowski

If you ever wondered how Linux kernel can handle multiple devices sharing the same GPIO, you got one more reason to go to Seattle this April:
https://sched.co/1aPvr

My second talk got accepted to LinuxCon / Open Source Summit NA 2024.
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Krzysztof Kozlowski

About current EU and Polish farmer protests, let's digest this meme. Left pic is from Poland, where Polish farmers protest with Soviet Union flag and banner saying:
"Puting clean up mess with Ukraine, Brussels and our government."

Right picture is from Ukraine (quite old btw)...
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In the face of hundreds of thousands murdered in Ukraine, and millions more displaced fleeing Russian military aggression, it is hard to focus on the death of one man. And yet, Navalny meant a lot to the Russian opposition and his death is just another proof that Putin's regime is criminal to the core and cannot be dealt with by appeasement or backroom deals. Ukrainians are the only force actively fighting the Kremlin mafia regime and we should continue to give them all they need to achieve a swift and decisive victory.
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Krzysztof Kozlowski

Is DT schema validation of DTS boards helpful or not? Get ready to find it out during my talk on EOSS 2024 conference in April:
https://sched.co/1aBEf
See you in Seattle!
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Krzysztof Kozlowski

10 years ago I sent a patch to fix one compatible in one Marvell SoC board:
https://lore.kernel.org/linux-devicetree/1410884282-18041-1-git-send-email-k.kozlowski@samsung.com/
Obvious fix but was never picked up.

In 2021 Sebastian tried to fix it:
https://lore.kernel.org/linux-devicetree/20210412230320.382885-2-sebastian.reichel@collabora.com/

Now in 2023 and 2024, Duje tries the same:
https://lore.kernel.org/linux-devicetree/20240125-brownstone-typo-fix-v2-1-45bc48a0c81c@skole.hr/

Will it succeed?
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Krzysztof Kozlowski

Linux v6.8-rc1 comes with new document describing coding style for DTS (Devicetree sources):
https://www.kernel.org/doc/html/latest/devicetree/bindings/dts-coding-style.html

This marks the end of many unwritten rules, varying between subsystems and maintainers. At least, like with every coding style document, in theory. :)
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Krzysztof Kozlowski

Edited 4 months ago
I was always using git branch --edit-description && git format-patch && git send-email, but now I tried preparing and sending patchset with b4 (b4 prep && b4 send). It works great! It is trivial in use and really solves the workflow. I cannot understand why people still Cc wrong people or are unable to send one patchset properly threaded.

Edit: --edit-cover->--edit-description
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FYI, Qualcomm Snapdragon X Elite (X1E80100) now boots to shell with today's -next.

More support is already sent on the list for review:
https://lore.kernel.org/all/?q=X1E80100

And here is a public branch with all support currently available on top of -next:
https://git.codelinaro.org/abel.vesa/linux/-/tree/x1e80100-next
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Krzysztof Kozlowski

Edited 5 months ago
Tensor is coming to the next Linux kernel: v6.8!
I just applied last patches for Linux kernel bringing support for the Google Tensor GS101 SoC (derivative of Samsung Exynos):
https://lore.kernel.org/linux-samsung-soc/170249498744.308886.17508790332822828341.b4-ty@linaro.org/T/#u

Commits will hit tomorrow's linux-next and probably next week I will send pull request with them to SoC (@arnd@society.oftrolls.com and Olof) for the next merge window. Good job Peter Griffin and @LinaroLtd :)
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I can finally reveal some research I've been involved with over the past year or so.

We (@redford, @mrtick and I) have reverse engineered the PLC code of NEWAG Impuls EMUs. These trains were locking up for arbitrary reasons after being serviced at third-party workshops. The manufacturer argued that this was because of malpractice by these workshops, and that they should be serviced by them instead of third parti
es.

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A reminder about what Muscovy did to us in 1932/33: https://en.wikipedia.org/wiki/Holodomor. Today is the Remembrance Day: https://en.wikipedia.org/wiki/Holodomor_Memorial_Day

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Today is the annual day of remembrance for the Holodomor, the Ukrainian famine. 90 years ago Stalin sent activists to confiscate food from Ukrainian peasants. Millions died.
To mark this day, Putin sent dozens of drones to attack Kyiv.
Like Stalin, Putin wants to erase Ukraine.

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Krzysztof Kozlowski

Edited 6 months ago
Looking at Devicetree sources changes (DTS) could give some insight into which ARM64 platforms are the most active. DTS represents the real hardware, thus any new hardware-block for an existing SoC, new SoC or new board, require new DTS changes. It's an approximation, easy to measure and still quite informative. Let's take a look - the most developed ARM64 platforms in the upstream Linux kernel since last LTS (v6.1):

$ git diff --dirstat=changes,1 v6.1..v6.6 -- arch/arm64/boot/dts/ | sort -nr
44.6% arch/arm64/boot/dts/qcom/
12.2% arch/arm64/boot/dts/ti/
10.4% arch/arm64/boot/dts/freescale/
10.1% arch/arm64/boot/dts/rockchip/
5.0% arch/arm64/boot/dts/nvidia/
4.3% arch/arm64/boot/dts/mediatek/
3.9% arch/arm64/boot/dts/renesas/
3.5% arch/arm64/boot/dts/apple/
3.4% (the rest)
2.2% arch/arm64/boot/dts/amlogic/

Almost 45% of all changes to ARM64-related hardware in the upstream kernel were for Qualcomm SoCs and boards. That's quite a stunning number.
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