[bootlin/training-materials updates] master: Revert "kernel-driver-development-debugging: Add dedicated slies about early printl WIP" (b40424e1)
Thomas Petazzoni
thomas.petazzoni at bootlin.com
Fri Oct 29 10:46:40 CEST 2021
Repository : https://github.com/bootlin/training-materials
On branch : master
Link : https://github.com/bootlin/training-materials/commit/b40424e1425f53974d2ea216f85629f35f48e8a5
>---------------------------------------------------------------
commit b40424e1425f53974d2ea216f85629f35f48e8a5
Author: Gregory CLEMENT <gregory.clement at bootlin.com>
Date: Wed Sep 15 14:35:27 2021 +0200
Revert "kernel-driver-development-debugging: Add dedicated slies about early printl WIP"
This reverts commit 6515dccd9c160be9ee061cb4cbc8e080d1b98b98.
The kernel debugging changes was WIP, so should not have been
committed yet.
>---------------------------------------------------------------
b40424e1425f53974d2ea216f85629f35f48e8a5
.../kernel-driver-development-debugging.tex | 20 ++++----------------
1 file changed, 4 insertions(+), 16 deletions(-)
diff --git a/slides/kernel-driver-development-debugging/kernel-driver-development-debugging.tex b/slides/kernel-driver-development-debugging/kernel-driver-development-debugging.tex
index 0250fc1d..dc925b42 100644
--- a/slides/kernel-driver-development-debugging/kernel-driver-development-debugging.tex
+++ b/slides/kernel-driver-development-debugging/kernel-driver-development-debugging.tex
@@ -100,22 +100,6 @@ dev_info(&pdev->dev, "in probe\n");
\end{itemize}
\end{frame}
-\begin{frame}
- \frametitle{Printing message early during the boot}
- \begin{itemize}
- \item Messages are visible only once the console driver has been initialized.
- \item The console driver is simpler than a complete serial driver
- and is initialize earlier than serial driver
- \item But core subsystem are still initialized before, such as
- memory, timer or interrupt, if a crash occurred there, then no
- message are visible
- \item on arm (32 bits) architecture most of the SoC implement the
- \code{early_printk} support
- \item \Activate it with kconfig{CONFIG_DEBUG_LL} and \kconfig{CONFIG_EARLYPRINTK} and add
- \code{earlyprintk} to the kernel command line.
- \end{itemize}
-\end{frame}
-
\begin{frame}
\frametitle{DebugFS}
A virtual filesystem to export debugging information to user space.
@@ -292,5 +276,9 @@ dev_info(&pdev->dev, "in probe\n");
\item Is turned on by default
\item To get oops messages with symbol names instead of raw addresses
\end{itemize}
+ \item On ARM, if your kernel doesn't boot or hangs without any
+ message, you can activate early debugging options
+ (\kconfig{CONFIG_DEBUG_LL} and \kconfig{CONFIG_EARLYPRINTK}), and add
+ \code{earlyprintk} to the kernel command line.
\end{itemize}
\end{frame}
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