[RFC 0/2] sandbox: add gpio support with libftdi1

[RFC 0/2] sandbox: add gpio support with libftdi1

[Antony Pavlov]

This patch series makes it possible to use FT2232H ACBUS[7:0]
pins as gpio pins from sandbox barebox.

I have tested output gpio functionality by connecting
a LED to ACBUS[0] and lightening it with gpio_direction_output
and gpio_set_value barebox commands.

Also I have performed input test with ACBUS[0] -> ACBUS[1] loopback.

The main goal of adding gpio functionality to sandbox barebox
is using it for connecting real i2c and spi devices to sandbox barebox
(not tested yet).


Antony Pavlov (2):
  sandbox: avoid symbol conflict for {open,read,close}dir
  sandbox: add gpio support with libftdi1

 arch/sandbox/Kconfig                           |   1 +
 arch/sandbox/Makefile                          |  10 +-
 arch/sandbox/board/board.c                     |   7 ++
 arch/sandbox/mach-sandbox/include/mach/linux.h |  11 ++
 arch/sandbox/os/Makefile                       |   3 +
 arch/sandbox/os/ftdi.c                         | 167 +++++++++++++++++++++++++
 drivers/gpio/Kconfig                           |   4 +
 drivers/gpio/Makefile                          |   1 +
 drivers/gpio/gpio-libftdi1.c                   | 116 +++++++++++++++++
 9 files changed, 318 insertions(+), 2 deletions(-)
 create mode 100644 arch/sandbox/os/ftdi.c
 create mode 100644 drivers/gpio/gpio-libftdi1.c

-- 
2.11.0


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[RFC 1/2] sandbox: avoid symbol conflict for {open,read,close}dir

[Antony Pavlov]

This fixes libusb's /dev/bus/usb directory scan.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
---
 arch/sandbox/Makefile | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/sandbox/Makefile b/arch/sandbox/Makefile
index 8155a790e..9d545c3b7 100644
--- a/arch/sandbox/Makefile
+++ b/arch/sandbox/Makefile
@@ -21,7 +21,9 @@ CFLAGS += -Dmalloc=barebox_malloc -Dcalloc=barebox_calloc \
 		-Dfputs=barebox_fputs -Dsetenv=barebox_setenv \
 		-Dgetenv=barebox_getenv -Dprintf=barebox_printf \
 		-Dglob=barebox_glob -Dglobfree=barebox_globfree \
-		-Dioctl=barebox_ioctl -Dfstat=barebox_fstat
+		-Dioctl=barebox_ioctl -Dfstat=barebox_fstat \
+		-Dopendir=barebox_opendir -Dreaddir=barebox_readdir \
+		-Dclosedir=barebox_closedir
 
 machdirs := $(patsubst %,arch/sandbox/mach-%/,$(machine-y))
 
-- 
2.11.0


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[RFC 2/2] sandbox: add gpio support with libftdi1

[Antony Pavlov]

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
---
 arch/sandbox/Kconfig                           |   1 +
 arch/sandbox/Makefile                          |   6 +-
 arch/sandbox/board/board.c                     |   7 ++
 arch/sandbox/mach-sandbox/include/mach/linux.h |  11 ++
 arch/sandbox/os/Makefile                       |   3 +
 arch/sandbox/os/ftdi.c                         | 167 +++++++++++++++++++++++++
 drivers/gpio/Kconfig                           |   4 +
 drivers/gpio/Makefile                          |   1 +
 drivers/gpio/gpio-libftdi1.c                   | 116 +++++++++++++++++
 9 files changed, 315 insertions(+), 1 deletion(-)

diff --git a/arch/sandbox/Kconfig b/arch/sandbox/Kconfig
index 9c72673bd..3f1cefb83 100644
--- a/arch/sandbox/Kconfig
+++ b/arch/sandbox/Kconfig
@@ -1,6 +1,7 @@
 config SANDBOX
 	bool
 	select OFTREE
+	select GPIOLIB
 	default y
 
 config ARCH_TEXT_BASE
diff --git a/arch/sandbox/Makefile b/arch/sandbox/Makefile
index 9d545c3b7..85c70b5e8 100644
--- a/arch/sandbox/Makefile
+++ b/arch/sandbox/Makefile
@@ -41,9 +41,13 @@ ifeq ($(CONFIG_DRIVER_VIDEO_SDL),y)
 SDL_LIBS := $(shell pkg-config sdl --libs)
 endif
 
+ifeq ($(CONFIG_GPIO_LIBFTDI1),y)
+FTDI1_LIBS := $(shell pkg-config libftdi1 --libs)
+endif
+
 cmd_barebox__ = $(CC) -o $@ -Wl,-T,$(barebox-lds) \
 	-Wl,--start-group $(barebox-common) -Wl,--end-group \
-	-lrt -lpthread $(SDL_LIBS)
+	-lrt -lpthread $(SDL_LIBS) $(FTDI1_LIBS)
 
 common-y += $(BOARD) arch/sandbox/os/
 
diff --git a/arch/sandbox/board/board.c b/arch/sandbox/board/board.c
index dcad3c249..5ab47e21c 100644
--- a/arch/sandbox/board/board.c
+++ b/arch/sandbox/board/board.c
@@ -42,6 +42,11 @@ static struct device_d sdl_device = {
 	.platform_data = &mode,
 };
 
+static struct device_d libftdi1_device = {
+	.id	  = DEVICE_ID_DYNAMIC,
+	.name     = "libftdi1-gpio",
+};
+
 static int devices_init(void)
 {
 	platform_device_register(&tap_device);
@@ -54,6 +59,8 @@ static int devices_init(void)
 
 	platform_device_register(&sdl_device);
 
+	platform_device_register(&libftdi1_device);
+
 	return 0;
 }
 
diff --git a/arch/sandbox/mach-sandbox/include/mach/linux.h b/arch/sandbox/mach-sandbox/include/mach/linux.h
index 1f11ed449..e52180ae4 100644
--- a/arch/sandbox/mach-sandbox/include/mach/linux.h
+++ b/arch/sandbox/mach-sandbox/include/mach/linux.h
@@ -38,4 +38,15 @@ void sdl_get_bitfield_rgba(struct fb_bitfield *r, struct fb_bitfield *g,
 			    struct fb_bitfield *b, struct fb_bitfield *a);
 void sdl_setpixel(int x, int y, uint8_t r, uint8_t g, uint8_t b, uint8_t a);
 
+struct ft2232_bitbang;
+struct ft2232_bitbang *barebox_libftdi1_open(void);
+void barebox_libftdi1_gpio_direction(struct ft2232_bitbang *ftbb,
+						unsigned off, unsigned dir);
+int barebox_libftdi1_gpio_get_value(struct ft2232_bitbang *ftbb,
+						unsigned off);
+void barebox_libftdi1_gpio_set_value(struct ft2232_bitbang *ftbb,
+						unsigned off, unsigned val);
+int barebox_libftdi1_update(struct ft2232_bitbang *ftbb);
+void barebox_libftdi1_close(void);
+
 #endif /* __ASM_ARCH_LINUX_H */
diff --git a/arch/sandbox/os/Makefile b/arch/sandbox/os/Makefile
index 537f848e0..75baa34a8 100644
--- a/arch/sandbox/os/Makefile
+++ b/arch/sandbox/os/Makefile
@@ -17,3 +17,6 @@ obj-y = common.o tap.o
 
 CFLAGS_sdl.o = $(shell pkg-config sdl --cflags)
 obj-$(CONFIG_DRIVER_VIDEO_SDL) += sdl.o
+
+CFLAGS_ftdi.o = $(shell pkg-config libftdi1 --cflags)
+obj-$(CONFIG_GPIO_LIBFTDI1) += ftdi.o
diff --git a/arch/sandbox/os/ftdi.c b/arch/sandbox/os/ftdi.c
new file mode 100644
index 000000000..b37903dd5
--- /dev/null
+++ b/arch/sandbox/os/ftdi.c
@@ -0,0 +1,167 @@
+/*
+ * sandbox barebox libftdi1 support
+ *
+ * Copyright (C) 2016, 2017 Antony Pavlov <antonynpavlov@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <ftdi.h>
+#include <errno.h>
+#include <mach/linux.h>
+
+#define GPIOF_DIR_OUT	(0 << 0)
+#define GPIOF_DIR_IN	(1 << 0)
+
+#define BIT(nr)			(1UL << (nr))
+
+struct ft2232_bitbang {
+	struct ftdi_context *ftdi;
+	uint8_t odata;
+	uint8_t dir;
+};
+
+static struct ft2232_bitbang ftbb;
+
+static inline int ftdi_flush(struct ftdi_context *ftdi)
+{
+	uint8_t buf[1];
+	int ret;
+
+	buf[0] = SEND_IMMEDIATE;
+
+	ret = ftdi_write_data(ftdi, buf, 1);
+
+	return ret;
+}
+
+static int ftdi_get_high_byte_data(struct ftdi_context *ftdi, uint8_t *data)
+{
+	uint8_t obuf;
+	int ret;
+
+	obuf = GET_BITS_HIGH;
+	ret = ftdi_write_data(ftdi, &obuf, 1);
+
+	ret = ftdi_read_data(ftdi, data, 1);
+
+	return ret;
+}
+
+static int ftdi_set_high_byte_data_dir(struct ft2232_bitbang *ftbb)
+{
+	uint8_t buf[3];
+	int ret;
+
+	buf[0] = SET_BITS_HIGH;
+	buf[1] = ftbb->odata;
+	buf[2] = ftbb->dir;
+
+	ret = ftdi_write_data(ftbb->ftdi, buf, 3);
+	ftdi_flush(ftbb->ftdi);
+
+	return ret;
+}
+
+int barebox_libftdi1_update(struct ft2232_bitbang *ftbb)
+{
+	return ftdi_set_high_byte_data_dir(ftbb);
+}
+
+void barebox_libftdi1_gpio_direction(struct ft2232_bitbang *ftbb,
+					unsigned off, unsigned dir)
+{
+	switch (dir) {
+	case GPIOF_DIR_IN:
+		ftbb->dir &= ~BIT(off);
+		break;
+	case GPIOF_DIR_OUT:
+		ftbb->dir |= BIT(off);
+		break;
+	default:
+		printf("%s:%d: invalid dir argument\n", __FILE__, __LINE__);
+	}
+}
+
+int barebox_libftdi1_gpio_get_value(struct ft2232_bitbang *ftbb, unsigned off)
+{
+	uint8_t data;
+
+	ftdi_get_high_byte_data(ftbb->ftdi, &data);
+
+	return !!(data & BIT(off));
+}
+
+void barebox_libftdi1_gpio_set_value(struct ft2232_bitbang *ftbb,
+					unsigned off, unsigned val)
+{
+	if (val)
+		ftbb->odata |= BIT(off);
+	else
+		ftbb->odata &= ~BIT(off);
+}
+
+int barebox_libftdi1_init(void)
+{
+	struct ftdi_context *ftdi;
+	int ret;
+
+	ftdi = ftdi_new();
+	if (!ftdi) {
+		fprintf(stderr, "ftdi_new failed\n");
+		goto error;
+	}
+
+	ret = ftdi_usb_open(ftdi, 0x0403, 0x6010);
+	if (ret < 0 && ret != -5) {
+		fprintf(stderr, "unable to open ftdi device: %d (%s)\n",
+			ret, ftdi_get_error_string(ftdi));
+		goto error;
+	}
+
+	ftdi_set_interface(ftdi, INTERFACE_A);
+	ftdi_set_bitmode(ftdi, 0x00, BITMODE_MPSSE);
+
+	ftbb.ftdi = ftdi;
+
+	/* reset pins to default neutral state */
+	ftbb.dir = 0;
+	ftbb.odata = 0;
+	ftdi_set_high_byte_data_dir(&ftbb);
+
+	return 0;
+
+error:
+	return -1;
+}
+
+struct ft2232_bitbang *barebox_libftdi1_open(void)
+{
+	if (barebox_libftdi1_init() < 0) {
+		printf("Could not initialize ftdi\n");
+		return NULL;
+	}
+
+	return &ftbb;
+}
+
+void barebox_libftdi1_close(void)
+{
+	struct ftdi_context *ftdi = ftbb.ftdi;
+
+	ftdi_set_interface(ftdi, INTERFACE_ANY);
+	ftdi_usb_close(ftdi);
+	ftdi_free(ftdi);
+}
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 434c5688b..ed93e868a 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -132,6 +132,10 @@ config GPIO_SX150X
 	  Say Y here to build support for the Semtec Sx150x I2C GPIO
 	  expander chip.
 
+config GPIO_LIBFTDI1
+	bool "libftdi1 driver"
+	depends on SANDBOX
+
 endmenu
 
 endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index f37dd08f1..f5ed876d5 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_GPIO_CLPS711X)	+= gpio-clps711x.o
 obj-$(CONFIG_GPIO_DIGIC)	+= gpio-digic.o
 obj-$(CONFIG_GPIO_GENERIC)	+= gpio-generic.o
 obj-$(CONFIG_GPIO_IMX)		+= gpio-imx.o
+obj-$(CONFIG_GPIO_LIBFTDI1)	+= gpio-libftdi1.o
 obj-$(CONFIG_GPIO_MXS)		+= gpio-mxs.o
 obj-$(CONFIG_GPIO_JZ4740)	+= gpio-jz4740.o
 obj-$(CONFIG_GPIO_MALTA_FPGA_I2C) += gpio-malta-fpga-i2c.o
diff --git a/drivers/gpio/gpio-libftdi1.c b/drivers/gpio/gpio-libftdi1.c
new file mode 100644
index 000000000..1ceb78029
--- /dev/null
+++ b/drivers/gpio/gpio-libftdi1.c
@@ -0,0 +1,116 @@
+/*
+ * libftdi1 sandbox barebox GPIO driver
+ *
+ * Copyright (C) 2016, 2017 Antony Pavlov <antonynpavlov@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <common.h>
+#include <errno.h>
+#include <gpio.h>
+#include <init.h>
+#include <malloc.h>
+#include <mach/linux.h>
+
+struct libftdi1_gpio_chip {
+	struct gpio_chip chip;
+	struct ft2232_bitbang *ftbb;
+};
+
+static int libftdi1_gpio_direction_input(struct gpio_chip *chip, unsigned off)
+{
+	struct libftdi1_gpio_chip *gpio =
+		container_of(chip, struct libftdi1_gpio_chip, chip);
+
+	barebox_libftdi1_gpio_direction(gpio->ftbb, off, GPIOF_DIR_IN);
+	barebox_libftdi1_update(gpio->ftbb);
+
+	return 0;
+}
+
+static int libftdi1_gpio_direction_output(
+	struct gpio_chip *chip, unsigned off, int value)
+{
+	struct libftdi1_gpio_chip *gpio =
+		container_of(chip, struct libftdi1_gpio_chip, chip);
+
+	barebox_libftdi1_gpio_set_value(gpio->ftbb, off, value);
+	barebox_libftdi1_gpio_direction(gpio->ftbb, off, GPIOF_DIR_OUT);
+	barebox_libftdi1_update(gpio->ftbb);
+
+	return 0;
+}
+
+static int libftdi1_gpio_get_value(struct gpio_chip *chip, unsigned off)
+{
+	struct libftdi1_gpio_chip *gpio =
+		container_of(chip, struct libftdi1_gpio_chip, chip);
+
+	return barebox_libftdi1_gpio_get_value(gpio->ftbb, off);
+}
+
+static void libftdi1_gpio_set_value(
+	struct gpio_chip *chip, unsigned off, int value)
+{
+	struct libftdi1_gpio_chip *gpio =
+		container_of(chip, struct libftdi1_gpio_chip, chip);
+
+	barebox_libftdi1_gpio_set_value(gpio->ftbb, off, value);
+	barebox_libftdi1_update(gpio->ftbb);
+}
+
+static struct gpio_ops libftdi1_gpio_ops = {
+	.direction_input = libftdi1_gpio_direction_input,
+	.direction_output = libftdi1_gpio_direction_output,
+	.get = libftdi1_gpio_get_value,
+	.set = libftdi1_gpio_set_value,
+};
+
+static int libftdi1_gpio_probe(struct device_d *dev)
+{
+	struct libftdi1_gpio_chip *gpio;
+	struct ft2232_bitbang *ftbb;
+	int ret;
+
+	ftbb = barebox_libftdi1_open();
+	if (!ftbb)
+		return -EIO;
+
+	gpio = xzalloc(sizeof(*gpio));
+
+	gpio->ftbb = ftbb;
+
+	gpio->chip.dev = dev;
+	gpio->chip.ops = &libftdi1_gpio_ops;
+	gpio->chip.base = 0;
+	gpio->chip.ngpio = 8;
+
+	ret = gpiochip_add(&gpio->chip);
+
+	dev_dbg(dev, "%d: probed gpio%d with base %d\n",
+			ret, dev->id, gpio->chip.base);
+
+	return 0;
+}
+
+static void libftdi1_gpio_remove(struct device_d *dev)
+{
+	barebox_libftdi1_close();
+}
+
+static struct driver_d libftdi1_gpio_driver = {
+	.name = "libftdi1-gpio",
+	.probe = libftdi1_gpio_probe,
+	.remove = libftdi1_gpio_remove,
+};
+device_platform_driver(libftdi1_gpio_driver);
-- 
2.11.0


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Re: [RFC 0/2] sandbox: add gpio support with libftdi1

[Sascha Hauer]

Hi Antony,

On Wed, Feb 15, 2017 at 10:12:25AM +0300, Antony Pavlov wrote:
> This patch series makes it possible to use FT2232H ACBUS[7:0]
> pins as gpio pins from sandbox barebox.
> 
> I have tested output gpio functionality by connecting
> a LED to ACBUS[0] and lightening it with gpio_direction_output
> and gpio_set_value barebox commands.
> 
> Also I have performed input test with ACBUS[0] -> ACBUS[1] loopback.
> 
> The main goal of adding gpio functionality to sandbox barebox
> is using it for connecting real i2c and spi devices to sandbox barebox
> (not tested yet).

I just read that the FT2232H can even do native I2C and SPI, so no gpio
bitbanging would be necessary. Would it be possible to use this mode
instead?

Otherwise I think there should be a possibility to specify which, if
any, FT2232H chip barebox uses.

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [RFC 0/2] sandbox: add gpio support with libftdi1

[Sascha Hauer]

On Thu, Feb 16, 2017 at 11:28:35AM +0300, Antony Pavlov wrote:
> On Thu, 16 Feb 2017 08:34:30 +0100
> Sascha Hauer <s.hauer@pengutronix.de> wrote:
> 
> > Hi Antony,
> > 
> > On Wed, Feb 15, 2017 at 10:12:25AM +0300, Antony Pavlov wrote:
> > > This patch series makes it possible to use FT2232H ACBUS[7:0]
> > > pins as gpio pins from sandbox barebox.
> > > 
> > > I have tested output gpio functionality by connecting
> > > a LED to ACBUS[0] and lightening it with gpio_direction_output
> > > and gpio_set_value barebox commands.
> > > 
> > > Also I have performed input test with ACBUS[0] -> ACBUS[1] loopback.
> > > 
> > > The main goal of adding gpio functionality to sandbox barebox
> > > is using it for connecting real i2c and spi devices to sandbox barebox
> > > (not tested yet).
> > 
> > I just read that the FT2232H can even do native I2C and SPI, so no gpio
> > bitbanging would be necessary.
> 
> I suppose that gpio support itself is valuable.
> 
> > Would it be possible to use this mode instead?
> 
> Yes, FT2232H has MPSSE acellerator.
> Using MPSSE one can increase FT2232 I2C/SPI performance dramatically.
> I have compared two FT2232 I2C realizations (bitbang and libmpsse,
> see https://github.com/frantony/mprog/tree/master/i2c_access).
> on reading of 8 KiB data block from I2C eeprom. libmpsse's bandwidth is 6 KiB per second,
> bitbang's bandwidth is only 73 bytes per second (nearly 100 times worse).
> 
> Alas, I have no time to realize ftdi fast i2c/spi support for barebox in the nearest future

Don't worry, I was only curious.

> 
> > Otherwise I think there should be a possibility to specify which, if
> > any, FT2232H chip barebox uses.
> 
> I'll add cmdline options to select FT2232H chips on USB bus in v2 patchseries.
> Also I'll check i2c bitbang support. I can connect ds1307 rtc or at24 eeprom).

Ok.

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [RFC 0/2] sandbox: add gpio support with libftdi1

[Antony Pavlov]

On Thu, 16 Feb 2017 08:34:30 +0100
Sascha Hauer <s.hauer@pengutronix.de> wrote:

> Hi Antony,
> 
> On Wed, Feb 15, 2017 at 10:12:25AM +0300, Antony Pavlov wrote:
> > This patch series makes it possible to use FT2232H ACBUS[7:0]
> > pins as gpio pins from sandbox barebox.
> > 
> > I have tested output gpio functionality by connecting
> > a LED to ACBUS[0] and lightening it with gpio_direction_output
> > and gpio_set_value barebox commands.
> > 
> > Also I have performed input test with ACBUS[0] -> ACBUS[1] loopback.
> > 
> > The main goal of adding gpio functionality to sandbox barebox
> > is using it for connecting real i2c and spi devices to sandbox barebox
> > (not tested yet).
> 
> I just read that the FT2232H can even do native I2C and SPI, so no gpio
> bitbanging would be necessary.

I suppose that gpio support itself is valuable.

> Would it be possible to use this mode instead?

Yes, FT2232H has MPSSE acellerator.
Using MPSSE one can increase FT2232 I2C/SPI performance dramatically.
I have compared two FT2232 I2C realizations (bitbang and libmpsse,
see https://github.com/frantony/mprog/tree/master/i2c_access).
on reading of 8 KiB data block from I2C eeprom. libmpsse's bandwidth is 6 KiB per second,
bitbang's bandwidth is only 73 bytes per second (nearly 100 times worse).

Alas, I have no time to realize ftdi fast i2c/spi support for barebox in the nearest future

> Otherwise I think there should be a possibility to specify which, if
> any, FT2232H chip barebox uses.

I'll add cmdline options to select FT2232H chips on USB bus in v2 patchseries.
Also I'll check i2c bitbang support. I can connect ds1307 rtc or at24 eeprom).

-- 
Best regards,
  Antony Pavlov

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Re: [RFC 0/2] sandbox: add gpio support with libftdi1

[Ian Abbott]

On 16/02/17 07:34, Sascha Hauer wrote:
> Hi Antony,
>
> On Wed, Feb 15, 2017 at 10:12:25AM +0300, Antony Pavlov wrote:
>> This patch series makes it possible to use FT2232H ACBUS[7:0]
>> pins as gpio pins from sandbox barebox.
>>
>> I have tested output gpio functionality by connecting
>> a LED to ACBUS[0] and lightening it with gpio_direction_output
>> and gpio_set_value barebox commands.
>>
>> Also I have performed input test with ACBUS[0] -> ACBUS[1] loopback.
>>
>> The main goal of adding gpio functionality to sandbox barebox
>> is using it for connecting real i2c and spi devices to sandbox barebox
>> (not tested yet).
>
> I just read that the FT2232H can even do native I2C and SPI, so no gpio
> bitbanging would be necessary. Would it be possible to use this mode
> instead?
>
> Otherwise I think there should be a possibility to specify which, if
> any, FT2232H chip barebox uses.

The MPSSE mode of the FT2232H can sort of do native I2C, but not in a 
strictly conforming way.  The I2C SDA needs to be connected to two pins 
on the FT2232H, one for output and one for input, and there is a 
"Drive-Only-Zero" option for the output to ensure it is only driven low, 
and tri-stated high.  However, the I2C SCL is only connected to an 
output pin on the FT2232H, and is always driven in both directions. 
Therefore, it does not support "clock-stretching" by I2C slaves (where a 
slave pulls the SCL line low until it is ready), because it cannot read 
back the state of the SCL line.  Worse, if an I2C slave is doing 
clock-stretching by driving SCL low, this will contend with the FT2232H 
driving SCL high at the same time.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@mev.co.uk> )=-
-=(                          Web: http://www.mev.co.uk/  )=-

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