Fork of alistair23 Linux kernel for reMarkable from https://github.com/alistair23/linux
![]() Replace the loop to calculate the pre-divider and count with two separate div64_u64() calculations. This makes the code easier to read and improves the precision. Three example cases: 1) 32.768kHz LPO clock for the SDIO wifi chip on Khadas VIM clock input: 500MHz (FCLK_DIV4) period: 30518ns duty cycle: 15259ns old algorithm: pre_div=0, cnt=15259 new algorithm: pre_div=0, cnt=15259 (no difference in calculated values) 2) PWM LED on Khadas VIM clock input: 24MHz (XTAL) period: 7812500ns duty cycle: 7812500ns old algorithm: pre_div=2, cnt=62004 new algorithm: pre_div=2, cnt=62500 Using a scope (24MHz sampling rate) shows the actual difference: - old: 7753000ns, off by -59500ns (0.7616%) - new: 7815000ns, off by +2500ns (0.032%) 3) Theoretical case where pre_div is different clock input: 24MHz (XTAL) period: 2730624ns duty cycle: 1365312ns old algorithm: pre_div=1, cnt=32768 new algorithm: pre_div=0, cnt=65534 Using a scope (24MHz sampling rate) shows the actual difference: - old: 2731000ns - new: 2731000ns (my scope is not precise enough to measure the difference if there's any) Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Reviewed-by: Neil Armstrong <narmstrong@baylibre.com> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com> |
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Documentation | ||
LICENSES | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.clang-format | ||
.cocciconfig | ||
.get_maintainer.ignore | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
COPYING | ||
CREDITS | ||
Kbuild | ||
Kconfig | ||
MAINTAINERS | ||
Makefile | ||
README |
README
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.