[PATCH v7 0/4] gpiolib: speed up GPIO array processing

Janusz Krzysztofik
2018-09-02T12:01:07Z

The goal is to boost performance of get/set array functions while
processing GPIO arrays which represent pins of a signle chip in
hardware order. If resulting performance is close to PIO, GPIO API
can be used for data I/O without much loss of speed.

Created and tested on a low end Amstrad Delta board with NAND driver
updated to use GPIO API for data I/O. Performance degrade compared to
PIO is much better than before the optimization though not quite
satisfactory on my test hardware.

Janusz Krzysztofik (4):
gpiolib: Pass bitmaps, not integer arrays, to get/set array
gpiolib: Identify arrays matching GPIO hardware
gpiolib: Pass array info to get/set array functions
gpiolib: Implement fast processing path in get/set array

Changelog:
v7:
- add more people to Cc: - authors and/or those who contributed most to
the drivers in scope of the change,
[PATCH v7 1/4] gpiolib: Pass bitmaps, not integer arrays, to get/set:
- avoid VLAs, use data source type bit number as bitmap size if not
constant - great recommendation by Peter Rosin, thanks,
- revert names of local variables declared with DECLARE_BITMAP() from
'value_bitmap' to original names of value arrays they replace (but not
'value_array') - inspired by Peter Rosin suggestion - thanks!
drivers/gpio/gpio-max3191x.c:
- use bitmap_alloc() to be more consistent with DECLARE_BITMAP() pattern
used by other consumers,
drivers/phy/motorola/phy-mapphone-mdm6600.c:
- no need to mask unused bits of val before its assignment to bitmap,
passing PHY_MDM6600_NR_CMD_LINES to gpiod_set_array_value() as array/
bitmap size provides sufficient protection.

v6:
[PATCH v6 1/4] gpiolib: Pass bitmaps, not integer arrays, to get/set
- use DECLARE_BITMAP() macro for declaring value_bitmap - great idea by
David Laight, thanks!
drivers/auxdisplay/hd44780.c:
- simplify the code and adjust comments as recommended by Geert
Uytterhoeven - thanks!,
drivers/i2c/muxes/i2c-mux-gpio.c:
- drop .values member of struct gpiomux - details provided by Peter
Rosin, thanks!,
drivers/mux/gpio.c:
- drop .val member of struct mux_gpio - details provided by Peter
Rosin, thanks!,
drivers/net/phy/mdio-mux-gpio.c:
- drop .values member of struct mdio_mux_gpio_state and its processsing.

v5:
[PATCH v5 1/4] gpiolib: Pass bitmaps, not integer arrays, to get/set
- drivers/i2c/muxes/i2c-mux-gpio.c:
- drop assigment of values to struct gpiomux.values, as recommended
by Peter Rosin - thanks!,
- mark the .values member of the structure as obsolete,
- drivers/mux/gpio.c:
- drop assigment of values to struct mux_gpio.val, also recommended
by Peter Rosin - thanks!,
- merk the .val member of the structure as obsolete,
- drivers/auxdisplay/hd44780.c:
- fix incorrect bitmap size,
- use >>= operator to simplify notation,
both catched by Miguel Ojeda - thanks!,
- add Cc: clauses as well as Acked-by: collected so far.
[PATCH v5 2/4] gpiolib: Identify arrays matching GPIO hardware
- add Cc: clause.
[PATCH v5 3/4] gpiolib: Pass array info to get/set array functions
- add Cc: clauses as well as Acked-by: collected so far.
[PATCH v5 4/4] gpiolib: Implement fast processing path in get/set
- add Cc: clause.

v4:
That series was a follow up of the former "mtd: rawnand: ams-delta: Use
gpio-omap accessors for data I/O" which already contained some changes
to gpiolib. Those previous attempts were commented by Borris Brezillon
who suggested using GPIO API modified to accept bitmaps, and by Linus
Walleij who suggested still more great ideas for further immprovement
of the proposed API changes - thanks!

diffstat:
Documentation/driver-api/gpio/board.rst | 15 +
Documentation/driver-api/gpio/consumer.rst | 48 +++-
drivers/auxdisplay/hd44780.c | 67 ++----
drivers/bus/ts-nbus.c | 20 --
drivers/gpio/gpio-max3191x.c | 16 +
drivers/gpio/gpiolib.c | 273 ++++++++++++++++++++++------
drivers/gpio/gpiolib.h | 15 +
drivers/i2c/muxes/i2c-mux-gpio.c | 16 -
drivers/mmc/core/pwrseq_simple.c | 15 -
drivers/mux/gpio.c | 16 -
drivers/net/phy/mdio-mux-gpio.c | 13 -
drivers/pcmcia/soc_common.c | 10 -
drivers/phy/motorola/phy-mapphone-mdm6600.c | 17 -
drivers/staging/iio/adc/ad7606.c | 12 -
drivers/tty/serial/serial_mctrl_gpio.c | 9
include/linux/gpio/consumer.h | 35 ++-
16 files changed, 396 insertions(+), 201 deletions(-)