#SPI, #Kinetis, and #NuttX

Some discoveries about Serial Peripheral Interface, Kinetis, and NuttX. Part of the work on Board Support Package (#BSP) for our board.

https://qeef.srht.site/post/spi-kinetis-and-nuttx/

Want a premium Linux shirt that actually looks good? 🐧📱

Our well-designed shirt (penguin holding a phone) is 100% cotton with a stitched penguin logo.

Available this weekend at the #FOSDEM #LinuxOnMobile stand.

Location: Building U, entrance UD2 — grab your size before they’re gone!

Model: @Standara3217

#FOSDEM2026 #MobileLinux #LinuxMobile #sdm845 #Mobian #Phosh #Linux

If you have interest in basic or more advanced computer architectures learning and teaching then I plan to visit #RISCV #FOSDEM devroom this Satturday. We can discuss even use of our #QtRvSim in the teaching. We are working on Sv32 and latter even Sv39 addition to extend this tool even for teaching operating system basic concepts. Tenative goal is to run MIT-PDOS one day. We have new #QtRvSim manual at our #CompArch site as well and revamped online training site (thanks to Jakub Pelc https://swpelc.eu/).

#RISCV The presentation slides on the RISC-V architecture have been extended for later readers, with a more detailed list of basic and RVA23-related extensions to cover topics discussed with students during lecture. See PDF. The link to the Linux kernel device tree for the discussed OrangePi.

Mistake in description on the slide 11: Apple M1 Firestorm core maximal load-store throughput is 3× LD + 1× ST in parallel or 2× LD + 2× ST in parallel. I have tried to keep pace and said incorrect numbers.

Based on my remote knowledge and a brief personal discussion on the way home together with @okias after the Mobile Linux collaborative day event in November, I believe the initial unfortunate event involving swap of he/they was unintended.

Just found that the 2026 edition of the Linux Plumbers Conference will be in Prague 🇨🇿 , Oct. 5-7, on the same week as Open Source Summit Europe and Embedded Linux Conference Europe.

Save the dates and see you there! That's too early to book my train tickets though 🤔

https://lpc.events/event/20/

“Dancing on bones.” Russian occupation authorities are reopening the Mariupol Drama Theatre, destroyed in a 2022 airstrike while hundreds of civilians sheltered inside, including children. Russia has denied hitting the theatre and claimed the damage was caused by an explosion detonated inside the building, which was proven untrue.

A Russian fairytale premiere at a mass grave, pure cynicism.

Upstreaming progress on Snapdragon 845 phones: OnePlus 6/6T now working with the Linux -next tree after a focused month of mainlining. Pixel 3 and Shift 6MQ followed with incremental enablement. Hard lessons in patch rebasing, subsystem reviews, and feedback from kernel maintainers. Real steps toward sustainable mainline support. Read more on the blog.

https://ixit.cz/blog/2025-12-21-upstreaming-0

#LinuxMobile #MobileLinux #sdm845 #OnePlus6 #OnePlus6T #Pixel3

@vaurora https://blog.liw.fi/posts/2022/goalposts/

Links to related Ticket Lock code example for individual architectures:

• x86_64 gcc 5.2 -std=gnu++1y -Wall -O3 -ffast-math -fverbose-asm -march=native -mtune=native
• MIPS gcc 5.4 -std=gnu++1y -Wall -O3 -ffast-math
• ARM64 gcc 6.3 -std=gnu++1y -Wall -O4
• ARM gcc 6.3.0 -std=gnu++1y -Wall -O4
• ARM gcc 6.3 -std=gnu++1y -Wall -O4 -march=armv7-a
• RISC-V (64-bits) gcc 12 -std=gnu++1y -Wall -O4 -march=rv64g

Kernel Spinlock documentation at LWN.net from test-and-set over ticket-spinlocks to scalable MCS locks and qspinlocks.

Much more precise and detailed texts (papers and books) about scalability including memory ordering by @paulmckrcu are linked from his page http://www2.rdrop.com/users/paulmck/. The detailed Summary of Memory Ordering choices for current CPU architectures is documented in the Table 15.5 Chapter 15. Advanced Synchronization: Memory Ordering of his book Is Parallel Programming Hard, And If So, What Can You Do About It?.

A link to the article about mentioned problem with atomic operations Linux 6.18 Merges Fix For “Catastrophic Performance Issue” On 64-bit ARM at Phoronix.com

@pavel The leap seconds are much smaller problem than attempt to convince whole world that it should update calendar by one day (edit: which is what is in the original post and I have stubled over it in another post again, so sorry for repeating)
rtc: rk808: Compensate for Rockchip calendar deviation on November 31st
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f076ef44a44d02ed91543f820c14c2c7dff53716
So I keep to vote for binary counter myself.

@pavel If you have somewhere defined what is the base regardless of the leap seconds then you can use leap seconds history or cumulative count. For simple BIOS like tools you can define that adjustment offset is stored in some
backed up RTC RAM register.

In general, I do not understand the legacy to keep time in RTC in minutes, hours, days, months and years. Every sane system wants to run in monotonic binary time in its kernel, same for time comparison and adjustments. So ideal chip would provide some ROM field to specify its timebase frequency and then provide single binary number long enough to rollover in some reasonable time, decades, centuries. Some field to store base and some service information would worth to be added. I understand that division by 60 has been heavy deal for some 8-bit chips and even PC BIOS programmers has problems to understand how to convert monotonic time to Gregorian calendar, then the nightmare has been conservation by graphic library called Windows. This library has been replaced by real OS model obtained with DEC employee acquisition, but it keeps by default RTC in local time, adjusts its time during daylight saving period. What should do Windows laptop, when you move between time-zones??? And again there is already option in registry to keep RTC in UTC... But keeping it in some epoch based seconds or milliseconds would be much easier for everybody. All these conversion done during virtualization, RTC loads, stores....

As a follow-up to the yesterday post — we’ve got C-PHY mode working on Qualcomm devices!

Yesterday, Petr Hodina and I managed to get the main camera running on the OnePlus 6 / 6T (Sony IMX519 sensor) — a huge step forward for mainline main camera support on many modern devices 🎉

You can check out the current progress and changes here (not yet mainline-ready, tested with 6.16+):

https://gitlab.com/dhxx/linux/-/commits/sdm845-6-17-cam-test

#Mobileobile #qualcomm #postmarketOS #Mobian #camera

@pavel Thanks. What has been the price of your piece? I see some with 256 GB Flash for a little above 3 kkč, which is about 130 EUR. 2 kkč for 128 GB version.

@pavel Please, what is the state of the WiFi on #oneplus6 on some close to mainline kernels? I am starting to consider to buy it for testing (i see 2 kkč to 3 kkč prices) but postmarketOS Device status list more WiFi problems. The OnePlus 6T does not list WiFi problems but audio is marked as partial only. Do you have some tips for some cheap bazaar in ČR or near to buy piece for experimenting?