change the MPC512x SPI controller's transmission routine to increase
throughput: allow the RX byte counter to "lag behind" the TX byte
counter while iterating over the transfer's data, only wait for the
remaining RX bytes at the very end of the transfer
this approach eliminates delays in the milliseconds range, transfer
times for e.g. 16MB of SPI flash data dropped from 31s to 9s, correct
operation was tested by continuously transferring and comparing data
from an SPI flash (more than 200GB in some 45 hours)
background information on the motivation:
one might assume that all the RX data should have been received when the
TX data was sent, given the fact that we are the SPI master and provide
all of the clock, but in practise there's a difference
the ISR is triggered when the TX FIFO became empty, while transmission
of the last item still occurs (from the TX hold and shift registers),
sampling RX data on the opposite clock edge compared to the TX data adds
another delay (half a bit period), and RX data needs to propagate from
the reception buffer to the RX FIFO depending on the specific SoC
implementation
to cut it short: a difference between TX and RX byte counters during
transmission is not just acceptable but should be considered the regular
case, only the very end of the transfer needs to make sure that all of
the RX data was received before deasserting the chip select and telling
the caller that transmission has completed
Signed-off-by: Gerhard Sittig <gsi@denx.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
mechanical edits before changing functionality, to reduce diffs
- rename variables to later tell remaining TX and RX apart
- use size_t for the current TX and RX length
(for better compatibility with the min() macro)
- remove unused members from the master data (sysclk, eofbyte)
- silence a checkpatch warning (braces around single statement)
Signed-off-by: Gerhard Sittig <gsi@denx.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
There is no need to disable transmitter/receiver after each loop
iteration and re-enable it for next loop iteration. Enable the
transmitter/receiver before xfer loop starts and disable it when
the whole transfer is done.
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Currently the driver only uses one internal chip select.
Add support for gpio chip selects configured by cs-gpios
DT binding.
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Some SPI slave devices require asserted chip select signal across
multiple transfer segments of an SPI message. Currently the driver
always de-asserts the internal SS signal for every single transfer
segment of the message and ignores the 'cs_change' flag of the
transfer description. Disable the internal chip select (SS) only
if this is needed and indicated by the 'cs_change' flag.
Without this change, each partial transfer of a surrounding
multi-part SPI transaction might erroneously change the SS
signal, which might prevent slaves from answering the request
that was sent in a previous transfer segment because the
transaction could be considered aborted (SS was de-asserted
before reading the response).
Reported-by: Gerhard Sittig <gerhard.sittig@ifm.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@vger.kernel.org
The driver should setup mode bits it supports, otherwise
adding an SPI device might fail even if the driver supports
the requested SPI mode.
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Remove deprecated cell-index property and use spi alias to
obtain the SPI PSC number used for SPI bus id.
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
CONFIG_HOTPLUG is going away as an option. As result the __dev*
markings will be going away.
Remove use of __devinit, __devexit_p, __devinitdata, __devinitconst,
and __devexit.
Bill Pemberton has done most of the legwork on this series. I've used
his script to purge the attributes from the drivers/gpio tree.
Reported-by: Bill Pemberton <wfp5p@virginia.edu>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
The call to spi_unregister_master() in the device remove function frees device
memory, and with it any device local data. However, device local data is still
accessed after the call to spi_unregister_master().
Acquire a reference to the SPI master device and release it after cleanup is
complete to solve the problem.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
For simple modules that contain a single platform_driver without any
additional setup code then ends up being a block of duplicated
boilerplate. This patch adds a new macro, module_platform_driver(),
which replaces the module_init()/module_exit() registrations with
template functions.
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Reviewed-by: Magnus Damm <magnus.damm@gmail.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Sort the SPI makefile and enforce the naming convention spi_*.c for
spi drivers.
This change also rolls the contents of atmel_spi.h into the .c file
since there is only one user of that particular include file.
v2: - Use 'spi-' prefix instead of 'spi_' to match what seems to be
be the predominant pattern for subsystem prefixes.
- Clean up filenames in Kconfig and header comment blocks
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Gerhard Sittig
Anatolij Gustschin
Grant Likely
Guenter Roeck