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fc9515c923
This adds a debug module parameter to aid in debugging transfer issues by printing info to the kernel log. When enabled, status values are collected in the interrupt routine and msg info in bcm2835_i2c_start_transfer(). This is done in a way that tries to avoid affecting timing. Having printk in the isr can mask issues. debug values (additive): 1: Print info on error 2: Print info on all transfers 3: Print messages before transfer is started The value can be changed at runtime: /sys/module/i2c_bcm2835/parameters/debug Example output, debug=3: [ 747.114448] bcm2835_i2c_xfer: msg(1/2) write addr=0x54, len=2 flags= [i2c1] [ 747.114463] bcm2835_i2c_xfer: msg(2/2) read addr=0x54, len=32 flags= [i2c1] [ 747.117809] start_transfer: msg(1/2) write addr=0x54, len=2 flags= [i2c1] [ 747.117825] isr: remain=2, status=0x30000055 : TA TXW TXD TXE [i2c1] [ 747.117839] start_transfer: msg(2/2) read addr=0x54, len=32 flags= [i2c1] [ 747.117849] isr: remain=32, status=0xd0000039 : TA RXR TXD RXD [i2c1] [ 747.117861] isr: remain=20, status=0xd0000039 : TA RXR TXD RXD [i2c1] [ 747.117870] isr: remain=8, status=0x32 : DONE TXD RXD [i2c1] Signed-off-by: Noralf Trønnes <noralf@tronnes.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.