dc56ecb81a
The 8250 driver can probe for many variants of the venerable 16550A serial port. Some of those probes involve long (20ms) mdelay calls, which delay system boot. Modern systems and virtual machines don't have those variants. Provide a Kconfig option to disable probes for 16550A variants. Disabling this speeds up the boot of a virtual machine with a serial console by more than 20ms (a substantial fraction of the ~100ms needed to boot a carefully configured VM). Before: [ +0.021919] 00:04: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A After: [ +0.000097] 00:04: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A Signed-off-by: Josh Triplett <josh@joshtriplett.org> Link: https://lore.kernel.org/r/20200111022513.GA166267@localhost Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.