• Linus Walleij's avatar
    spi: spi-gpio: Rewrite to use GPIO descriptors · 9b00bc7b
    Linus Walleij authored
    This converts the bit-banged GPIO SPI driver to looking up and
    using GPIO descriptors to get a handle on GPIO lines for SCK,
    MOSI, MISO and all CS lines.
    
    All existing board files are converted in one go to keep it all
    consistent. With these conversions I rarely find any interrim
    steps that makes any sense.
    
    Device tree probing and GPIO handling should work like before
    also after this patch.
    
    For board files, we stop using controller data to pass the GPIO
    line for chip select, instead we pass this as a GPIO descriptor
    lookup like everything else.
    
    In some s3c24xx machines the names of the SPI devices were set to
    "spi-gpio" rather than "spi_gpio" which can never have worked, I
    fixed it working (I guess) as part of this patch set. Sometimes
    I wonder how this code got upstream in the first place, it
    obviously is not tested.
    
    mach-s3c64xx/mach-smartq.c has the same problem and additionally
    defines the *same* GPIO line for MOSI and MISO which is not going
    to be accepted by gpiolib. As the lines were number 1,2,2 I assumed
    it was a typo and use lines 1,2,3. A comment gives awat that line 0
    is chip select though no actual SPI device is provided for the LCD
    supposed to be on this bit-banged SPI bus. I left it intact instead
    of just deleting the bus though.
    
    Kill off board file code that try to initialize the SPI lines
    to the same values that they will later be set by the spi_gpio
    driver anyways. Given the huge number of weird things in these
    board files I do not think this code is very tested or put in
    with much afterthought anyways.
    
    In order to assert that we do not get performance regressions on
    this crucial bing-banged driver, a ran a script like this dumping the
    Ilitek ILI9322 regmap 10000 times (it has no caching obviously) on
    an otherwise idle system in two iterations before and after the
    patches:
    
     #!/bin/sh
     for run in `seq 10000`
     do
         cat /debug/regmap/spi0.0/registers > /dev/null
     done
    
    Before the patch:
    
    time test.sh
    real    3m 41.03s
    user    0m 29.41s
    sys     3m 7.22s
    
    time test.sh
    real    3m 44.24s
    user    0m 32.31s
    sys     3m 7.60s
    
    After the patch:
    
    time test.sh
    real    3m 41.32s
    user    0m 28.92s
    sys     3m 8.08s
    
    time test.sh
    real    3m 39.92s
    user    0m 30.20s
    sys     3m 5.56s
    
    So any performance differences seems to be in the error margin.
    Signed-off-by: 's avatarLinus Walleij <linus.walleij@linaro.org>
    Acked-by: 's avatarOlof Johansson <olof@lixom.net>
    Reviewed-by: 's avatarAndy Shevchenko <andy.shevchenko@gmail.com>
    Signed-off-by: 's avatarMark Brown <broonie@kernel.org>
    9b00bc7b
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