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197ecadad8
I got an idea the i2c-designware should not need duplicated state machines for the interrupt and polling modes. The IP is practically the same and state transitions happens in response to the events that can be observed from the DW_IC_RAW_INTR_STAT register. Either by interrupts or by polling. Another reasons are the interrupt mode is the most tested, has handling for special cases as well as transmit abort handling and those are missing from two polling mode quirks. Patch implements a generic polling mode by using existing code for interrupt mode. This is done by moving event handling from the i2c_dw_isr() into a new i2c_dw_process_transfer() that will be called both from the i2c_dw_isr() and a polling loop. Polling loop is implemented in a new i2c_dw_wait_transfer() that is shared between both modes. In interrupt mode it waits for the completion object as before. In polling mode both completion object and DW_IC_RAW_INTR_STAT are polled to determine completed transfer and state transitions. Loop tries to save power by sleeping "stetson guessed" range between 3 and 25 µS which falls between 10 cycles of High-speed mode 3.4 Mb/s and Fast mode 400 kHz. With it the CPU usage was reduced under heavy Fast mode I2C transfer without much increase in total transfer time but otherwise no more effort has been put to optimize this. I decided to convert the txgbe_i2c_dw_xfer_quirk() straight to generic polling mode code in this patch. It doesn't have HW dependent quirks like the amd_i2c_dw_xfer_quirk() does have and without users this patch is needless. Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> Tested-by: Jiawen Wu <jiawenwu@trustnetic.com> Signed-off-by: Andi Shyti <andi.shyti@kernel.org> |
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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.