spi: spi-gpio: Rewrite to use GPIO descriptors

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: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 25 insertions, 4 deletions

diff --git a/drivers/misc/eeprom/digsy_mtc_eeprom.c b/drivers/misc/eeprom/digsy_mtc_eeprom.c
index 66d9e1baeae5..fbde2516c04f 100644
--- a/drivers/misc/eeprom/digsy_mtc_eeprom.c
+++ b/drivers/misc/eeprom/digsy_mtc_eeprom.c
@@ -7,9 +7,18 @@
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
+ *
+ * FIXME: this driver is used on a device-tree probed platform: it
+ * should be defined as a bit-banged SPI device and probed from the device
+ * tree and not like this with static grabbing of a few numbered GPIO
+ * lines at random.
+ *
+ * Add proper SPI and EEPROM in arch/powerpc/boot/dts/digsy_mtc.dts
+ * and delete this driver.
  */
 
 #include <linux/gpio.h>
+#include <linux/gpio/machine.h>
 #include <linux/init.h>
 #include <linux/platform_device.h>
 #include <linux/spi/spi.h>
@@ -42,9 +51,6 @@ struct eeprom_93xx46_platform_data digsy_mtc_eeprom_data = {
 };
 
 static struct spi_gpio_platform_data eeprom_spi_gpio_data = {
-	.sck		= GPIO_EEPROM_CLK,
-	.mosi		= GPIO_EEPROM_DI,
-	.miso		= GPIO_EEPROM_DO,
 	.num_chipselect	= 1,
 };
 
@@ -56,6 +62,21 @@ static struct platform_device digsy_mtc_eeprom = {
 	},
 };
 
+static struct gpiod_lookup_table eeprom_spi_gpiod_table = {
+	.dev_id         = "spi_gpio",
+	.table          = {
+		GPIO_LOOKUP("gpio@b00", GPIO_EEPROM_CLK,
+			    "sck", GPIO_ACTIVE_HIGH),
+		GPIO_LOOKUP("gpio@b00", GPIO_EEPROM_DI,
+			    "mosi", GPIO_ACTIVE_HIGH),
+		GPIO_LOOKUP("gpio@b00", GPIO_EEPROM_DO,
+			    "miso", GPIO_ACTIVE_HIGH),
+		GPIO_LOOKUP("gpio@b00", GPIO_EEPROM_CS,
+			    "cs", GPIO_ACTIVE_HIGH),
+		{ },
+	},
+};
+
 static struct spi_board_info digsy_mtc_eeprom_info[] __initdata = {
 	{
 		.modalias		= "93xx46",
@@ -63,7 +84,6 @@ static struct spi_board_info digsy_mtc_eeprom_info[] __initdata = {
 		.bus_num		= EE_SPI_BUS_NUM,
 		.chip_select		= 0,
 		.mode			= SPI_MODE_0,
-		.controller_data	= (void *)GPIO_EEPROM_CS,
 		.platform_data		= &digsy_mtc_eeprom_data,
 	},
 };
@@ -78,6 +98,7 @@ static int __init digsy_mtc_eeprom_devices_init(void)
 		pr_err("can't request gpio %d\n", GPIO_EEPROM_OE);
 		return ret;
 	}
+	gpiod_add_lookup_table(&eeprom_spi_gpiod_table);
 	spi_register_board_info(digsy_mtc_eeprom_info,
 				ARRAY_SIZE(digsy_mtc_eeprom_info));
 	return platform_device_register(&digsy_mtc_eeprom);