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This patch is the result of work by both Jon Nettleton and Russell King.
Jon wrote the original patch, adding support for SFP modules which
require a power level greater than '1'.
Russell's changes:
- Fix the power levels for big-endian, and make the code flow better.
- Convert to use device_property_read_u8()
- Warn for power levels exceeding host level
SFF-8431 says:
"To avoid exceeding system power supply limits and cooling capacity,
all modules at power up by default shall operate with up to 1.0 W.
Hosts supporting Power Level II or III operation may enable a Power
Level II or III module through the 2-wire interface. Power Level II
or III modules shall assert the power level declaration bit of
SFF-8472."
Print a warning for modules that exceed the host power level, and
leave them operating in power level 1.
- Fix i2c write
The first byte of any write after the bus address is always the
device address. In order to write a value to device D, address I,
value V, we need to generate on the bus:
S DDDDDDDD A IIIIIIII A VVVVVVVV A P
where S = start, R = restart, A = ack, P = stop. Splitting this
as two:
S DDDDDDDD A IIIIIIII A R DDDDDDDD A VVVVVVVV A P
results in the device's address register being written first by I
and then by V - the addressed register within the device is not
written.
- Avoid power mode switching if 0xa2 is not implemented
Some modules indicate that they support power level II or power level
III, but do not implement address 0xa2, meaning that the bit to set
them to high power mode is not accessible.
These modules appear to have the sff8472_compliance field set to zero,
and also do not implement diagnostics. Detect this, but also ensure
that the module does not require the address switching mode, which we
do not implement.
- Use mW for power level rather than power level number.
- Fix high power mode transition
We must not switch to SFP_MOD_PRESENT state until we have finished
initialising, because the remaining state machines check for that
state. Add SFP_MOD_HPOWER as an intermediate state.
- Use definition for I2C register address rather than constant.
Signed-off-by: Jon Nettleton <jon@solid-run.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
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.