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The work-around for Qualcomm Technologies QDF2400 Erratum 44 hinges on a
global variable defined in the pl011 driver. The ACPI SPCR parsing code
determines whether the work-around is needed, and if so, it changes the
console name from "pl011" to "qdf2400_e44". The expectation is that
the pl011 driver will implement the work-around when it sees the console
name. The global variable qdf2400_e44_present is set when that happens.
The problem is that work-around needs to be enabled when the pl011
driver probes, not when the console name is queried. However, sbsa_probe()
is called before pl011_console_match(). The work-around appeared to work
previously because the default console on QDF2400 platforms was always
ttyAMA1. The first time sbsa_probe() is called (for ttyAMA0),
qdf2400_e44_present is still false. Then pl011_console_match() is called,
and it sets qdf2400_e44_present to true. All subsequent calls to
sbsa_probe() enable the work-around.
The solution is to move the global variable into spcr.c and let the
pl011 driver query it during probe time. This works because all QDF2400
platforms require SPCR, so parse_spcr() will always be called.
pl011_console_match still checks for the "qdf2400_e44" console name,
but it doesn't do anything else special.
Fixes: 5a0722b898 ("tty: pl011: use "qdf2400_e44" as the earlycon name for QDF2400 E44")
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.