Roland-Smith-Imperial

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SPI Bus performance loss of ~9% under Python moving from Kernel 6.6.31 -> 6.12.25

Oops, apologies for the messy formatting of that python code !

SPI Bus performance loss of ~9% under Python moving from Kernel 6.6.31 -> 6.12.25

Hi Tim Many thanks for the suggestion, I gave the PREEMPT_RT kernel variant a go as suggested above, it is still a slight "downgrade" in terms of average sample rate...

SPI Bus performance loss of ~9% under Python moving from Kernel 6.6.31 -> 6.12.25

![Image](https://github.com/user-attachments/assets/0cd7b438-2007-4c94-8fa0-c0b468ec5abd) ![Image](https://github.com/user-attachments/assets/861a9d03-0f4b-428d-8a71-7841318c5202)

SPI Bus performance loss of ~9% under Python moving from Kernel 6.6.31 -> 6.12.25

Histogram for a "standard" 6.12.28 kernel in non-RT mode below for comparison.

SPI Bus performance loss of ~9% under Python moving from Kernel 6.6.31 -> 6.12.25

![Image](https://github.com/user-attachments/assets/4726be15-723c-4dd2-9071-72c397e1a69b)

SPI Bus performance loss of ~9% under Python moving from Kernel 6.6.31 -> 6.12.25

Many thanks to popcornmix, pelwell, P33M and timg236 for all your insights much appreciated. It sounds like the (minor) slow down we see is the result of some pretty deep...

SPI Bus performance loss of ~9% under Python moving from Kernel 6.6.31 -> 6.12.25

>> https://github.com/raspberrypi/linux/pull/6862 is a trial patch to reduce (remove?) the overhead of the GPIO chip safety measures. Many thanks, that's very helpful, happy to give some beta software a go,...