Kenneth Kasilag
8db23dc91a
During testing on the Askey SBE1V1K, it was noticed that only very low
PWM frequencies would work, and 100% duty cycles also did not work.
Comparing the proposed upstream pwm-ipq driver to the downstream vendor
driver, `ipq_pwm_apply()` fixed pwm_div at its maximum and derived only
pre_div from the requested period. Since the period spans
`(pre_div + 1) * (pwm_div + 1)` input clocks, pinning pwm_div near its
maximum forces pre_div towards zero for short periods: once pre_div
rounds to 0 the shortest representable period is
`(pwm_div + 1) / clk_rate` (~2.7 ms, i.e. ~366 Hz, at a 24 MHz clock),
and any shorter request is silently stretched to that. The high
duration then truncates to 0, so the output collapses to ~0% duty.
Since 4-wire fans commonly expect a ~25kHz PWM, it was effectively
unusable, since every duty cycle programs a ~zero high time.
Search for the (pre_div, pwm_div) pair whose period best approximates
the request instead of fixing pwm_div. Starting pre_div at the smallest
value that keeps pwm_div within its field and stopping once pre_div
exceeds pwm_div bounds the loop and keeps pwm_div as large as possible
for fine duty resolution. For a 25 kHz request at 24 MHz this selects
pre_div = 0, pwm_div = 959, giving full 0..960 duty resolution.
While reworking the high-duration computation, round it to nearest
rather than truncating, so mid-range duty cycles are not biased low, and
clamp it to pwm_div + 1. Rounding, or a 100% duty request, could
otherwise push hi_dur past the period length and overflow the 16-bit
HI_DURATION field.
Also compute hi_div in `get_state()` in 64-bit; `hi_dur * (pre_div + 1)`
can exceed 32 bits before the existing promotion.
Fixes: 01fb4a6daa ("qualcommbe: update pwm patches and add missing symbol")
Signed-off-by: Kenneth Kasilag <kenneth@kasilag.me>
Link: https://github.com/openwrt/openwrt/pull/23916
Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
OpenWrt Project is a Linux operating system targeting embedded devices. Instead of trying to create a single, static firmware, OpenWrt provides a fully writable filesystem with package management. This frees you from the application selection and configuration provided by the vendor and allows you to customize the device through the use of packages to suit any application. For developers, OpenWrt is the framework to build an application without having to build a complete firmware around it; for users this means the ability for full customization, to use the device in ways never envisioned.
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Download
Built firmware images are available for many architectures and come with a package selection to be used as WiFi home router. To quickly find a factory image usable to migrate from a vendor stock firmware to OpenWrt, try the Firmware Selector.
If your device is supported, please follow the Info link to see install instructions or consult the support resources listed below.
An advanced user may require additional or specific package. (Toolchain, SDK, ...) For everything else than simple firmware download, try the wiki download page:
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To build your own firmware you need a GNU/Linux, BSD or macOS system (case sensitive filesystem required). Cygwin is unsupported because of the lack of a case sensitive file system.
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You need the following tools to compile OpenWrt, the package names vary between distributions. A complete list with distribution specific packages is found in the Build System Setup documentation.
binutils bzip2 diff find flex gawk gcc-6+ getopt grep install libc-dev libz-dev
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Run
./scripts/feeds update -ato obtain all the latest package definitions defined in feeds.conf / feeds.conf.default -
Run
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Run
make menuconfigto select your preferred configuration for the toolchain, target system & firmware packages. -
Run
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LuCI Web Interface: Modern and modular interface to control the device via a web browser.
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OpenWrt Packages: Community repository of ported packages.
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OpenWrt Routing: Packages specifically focused on (mesh) routing.
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OpenWrt Video: Packages specifically focused on display servers and clients (Xorg and Wayland).
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