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Phil Elwell 491b17eefe w1: w1-gpio: Make GPIO an output for strong pullup
The logic to drive the data line high to implement a strong pullup
assumed that the pin was already an output - setting a value does
not change an input.

See: https://github.com/raspberrypi/firmware/issues/1143

Signed-off-by: Phil Elwell <phil@raspberrypi.org>

drivers: w1-gpio: add flag to force read-polling while delaying

On Pi 5, the link to RP1 will bounce in and out of L1 depending on
inactivity timers at both the RC and EP end. Unfortunately for
bitbashing 1-wire, this means that on an otherwise idle Pi 5 many of the
reads/writes to GPIO registers are delayed by up to 8us which causes
mis-sampling of read data and trashes write bits.

By issuing dummy reads at a rate greater than the link inactivity
timeout while spinning on a delay, PCIe stays in L0 which does not incur
additional latency.

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>

drivers: w1-gpio: Fixup uninitialised variable use in w1_gpio_probe

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
2025-12-01 15:36:59 +00:00
2025-12-01 11:45:37 +01:00
2025-12-01 11:46:09 +01:00

Linux kernel

There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first.

In order to build the documentation, use make htmldocs or make pdfdocs. The formatted documentation can also be read online at:

https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.

Build status for rpi-6.1.y: Pi kernel build tests dtoverlaycheck

Build status for rpi-6.6.y: Pi kernel build tests dtoverlaycheck

Build status for rpi-6.12.y: Pi kernel build tests dtoverlaycheck

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