Backport the upstream PWM GPIO driver from 6.11 to rpi-6.6.y #6450
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
commit 7f61257 upstream. Add a software PWM which toggles a GPIO from a high-resolution timer. This will naturally not be as accurate or as efficient as a hardware PWM, but it is useful in some cases. I have for example used it for evaluating LED brightness handling (via leds-pwm) on a board where the LED was just hooked up to a GPIO, and for a simple verification of the timer frequency on another platform. Since high-resolution timers are used, sleeping GPIO chips are not supported and are rejected in the probe function. Signed-off-by: Vincent Whitchurch <[email protected]> Co-developed-by: Stefan Wahren <[email protected]> Signed-off-by: Stefan Wahren <[email protected]> Co-developed-by: Linus Walleij <[email protected]> Reviewed-by: Andy Shevchenko <[email protected]> Signed-off-by: Linus Walleij <[email protected]> Reviewed-by: Dhruva Gole <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Uwe Kleine-König <[email protected]> Signed-off-by: Tim Gover <[email protected]> pwm: Backport pwm-gpio.c to rpi-6.6.y
|
The usual set of defconfigs is: We don't use |
Enable the PWM GPIO module in Raspberry Pi kernels. Signed-off-by: Tim Gover <[email protected]>
Signed-off-by: Tim Gover <[email protected]>
timg236
force-pushed
the
rpi-6.6.y-pwm-gpio
branch
from
07ee2d3
to
5567cb3
Compare
|
@Gadgetoid FYI, the backport of the pwm-gpio should be in rpi-update relatively soon. It worked ok on a Pi5 with a MG946 servo and seemed solid under normal loads. Maxing out the PCIe link can cause a very small but observable wobble on the servo. |
|
Thank you! Can confirm this works from source (rpi-update hasn't got the memo just yet). From my earlier testing jitter and accuracy were lightyears ahead of the common userspace software PWM alternatives. It's just a shame the |
popcornmix
added a commit
to raspberrypi/firmware
that referenced
this pull request
Nov 5, 2024
See: raspberrypi/linux#6450 kernel: dts: 2712: Drop some numa options from bootargs See: raspberrypi/linux#6434
popcornmix
added a commit
to raspberrypi/rpi-firmware
that referenced
this pull request
Nov 5, 2024
See: raspberrypi/linux#6450 kernel: dts: 2712: Drop some numa options from bootargs See: raspberrypi/linux#6434
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Backport this driver to provide bit bashed PWM support on an arbitrary GPIO pin.
On Pi5 this is considerably faster than doing this from user space but this is still constrained somewhat by PCIe latency and jitter if the PCIe link is under a high load (e.g. USB3). This should still be suitable for simple applications like servos.