[FE training-materials-updates] kernel-serial-iomem: Update instructions for the beaglebone

[Maxime Ripard]

Repository : git://git.free-electrons.com/training-materials.git

On branch  : kernel-bbb
Link       : http://git.free-electrons.com/training-materials/commit/?id=ddcee90987fab2e75d6fa31504bc02878125d3cd

>---------------------------------------------------------------

commit ddcee90987fab2e75d6fa31504bc02878125d3cd
Author: Maxime Ripard <maxime.ripard at free-electrons.com>
Date:   Fri Sep 6 14:03:46 2013 +0200

    kernel-serial-iomem: Update instructions for the beaglebone
    
    Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>


>---------------------------------------------------------------

ddcee90987fab2e75d6fa31504bc02878125d3cd
 labs/kernel-serial-iomem/kernel-serial-iomem.tex |   45 +++++++++++-----------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/labs/kernel-serial-iomem/kernel-serial-iomem.tex b/labs/kernel-serial-iomem/kernel-serial-iomem.tex
index bfe14b6..bb81afc 100644
--- a/labs/kernel-serial-iomem/kernel-serial-iomem.tex
+++ b/labs/kernel-serial-iomem/kernel-serial-iomem.tex
@@ -2,7 +2,7 @@
   write data from / to a hardware device}
 
 Throughout the upcoming labs, we will implement a character driver
-allowing to write data to the serial port of the CALAO board, and to
+allowing to write data to the serial port of the BeagleBone, and to
 read data from it.
 
 After this lab, you will be able to:
@@ -25,18 +25,18 @@ After this lab, you will be able to:
 Go to the \code{$HOME/felabs/linux/character} directory.
 
 As in the {\em Module development environment} lab, we will use a the
-CALAO board booted from NFS.
+BeagleBone booted from NFS.
 
 As in the previous labs, the target IP address will be \code{192.168.0.100},
 and the host address will be \code{192.168.0.1}.
 
-Extract the latest Linux 3.6.x kernel sources in the current
+Extract the latest Linux 3.11.x kernel sources in the current
 directory, and configure them with the default configuration for
-{\em at91sam9263} boards.
+the {\em omap2plus} architecture.
 
 In this lab, we will develop our own driver for the board's serial
 port. The consequence is that we will have to disable the standard
-AT91 serial port driver and will thus lose the serial console.
+OMAP serial port driver and will thus lose the serial console.
 
 Instead of running commands through a shell on the serial line, we
 will access our target through SSH, a secure shell over the network.
@@ -52,6 +52,8 @@ So, configure your kernel with:
 \item Netconsole support (\code{CONFIG_NETCONSOLE})
 \end{itemize}
 
+and disable \code{CONFIG_DEVTMPFS}
+
 You will also have to update the kernel command line so that Linux
 loads the root filesystem over NFS from
 \code{/home/<user>/felabs/linux/character/nfsroot}.
@@ -77,11 +79,11 @@ The \code{root} password is empty, just press \code{Enter}. Good job!
 \section{Disabling the serial driver and console}
 
 Now that everything works, rebuild your kernel without the serial port
-driver (in \code{Device Drivers} $\rightarrow$ \code{Character devices}
-$\rightarrow$ \code{Serial drivers} $\rightarrow$ \code{AT91 / AT32
-on-chip serial port support}). Update your kernel.
+driver (in \code{Device Drivers} $\rightarrow$
+\code{Character devices} $\rightarrow$ \code{Serial drivers}
+$\rightarrow$ \code{OMAP serial port support}). Update your kernel.
 
-You also need to replace \code{console=ttyS0} by the following option in
+You also need to replace \code{console=ttyO0} by the following option in
 the kernel command line, to enable the network console:
 
 \begin{verbatim}
@@ -110,9 +112,9 @@ code. Modify the \code{Makefile} so that it points to your kernel sources.
 \section{Device initialization}
 
 In the module initialization function, start by reserving the I/O
-memory region starting at address (\code{AT91_BASE_DBGU1}), for a
-size of \code{SZ_512} (512 bytes). The \code{AT91_*} constants are already defined
-in Linux kernel headers.
+memory region starting at address (\code{0x44e09000}), for a size of
+\code{SZ_512} (512 bytes). The \code{UART} constants are already
+defined in Linux kernel headers (\code{serial_reg.h}).
 
 Compile your module, load it and make sure that this memory region
 appears in \code{/proc/iomem}.
@@ -128,20 +130,19 @@ Implement a C routine taking one character as a parameter and writing
 it to the serial port, using the following steps:
 
 \begin{enumerate}
+\item Wait until the \code{UART_LSR_THRE} bit gets set in the
+  \code{UART_LSR} register (\code{UART_LSR} is an index number for
+  this register. You'll have to multiply it by 4 to get an offset in
+  the I/O memory region previously remapped). You can busy-wait for
+  this condition to happen. In the busy-wait loop, you can call the
+  \code{cpu_relax()} kernel function to ensure the compiler won't
+  optimise away this loop.
 
- \item Wait until the \code{ATMEL_US_TXRDY} bit gets set in
- the \code{ATMEL_US_CSR} register (\code{ATMEL_US_CSR} is an
- offset in the I/O memory region previously remapped). You can
- busy-wait for this condition to happen. In the busy-wait loop, you
- can call the \code{cpu_relax()} kernel function to relax the CPU
- during the wait.
-
- \item Write the character to the \code{ATMEL_US_THR} register.
+\item Write the character to the \code{UART_TX} register.
 
 \end{enumerate}
 
-Note that all the I/O registers of the AT91 processor are 32 bits
-wide.
+Note that all the I/O registers of the AM335x SoC are 32 bits wide.
 
 Add a call to this routine from your module init function. Recompile
 your module and load it on the target. You should see the