Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
On Wed, Sep 19, 2012 at 11:08:13PM +0300, Aaro Koskinen wrote: > On Fri, Sep 14, 2012 at 12:08:06PM +0200, Wolfram Sang wrote: > > On Mon, Sep 03, 2012 at 11:23:22PM +0300, Aaro Koskinen wrote: > > > Add i2c driver to enable access to devices behind CBUS on Nokia Internet > > > Tablets. > > > > > > The patch also adds CBUS I2C configuration for N8x0 which is one of the > > > users of this driver. > > > > > > Cc: linux-...@vger.kernel.org > > > Acked-by: Felipe Balbi > > > Acked-by: Tony Lindgren > > > Signed-off-by: Aaro Koskinen > > > > OK, I found the short paragrahp about CBUS in the I2C spec, so I2C might > > be an appropriate place. Still, before deciding if it should rather be > > in the core directory, I still have a few questions. > > Thanks for your feedback. I will fix up the incorrect comments, and do > other improvements (e.g. use devm_* stuff) in the next version. > > The questions about delays and bit counts are very valid, but it's > difficult to do anything with them due to lack of documentation and HW on > which to test - I have Nokia tablets to test the driver, and the driver > is very reliable, but I do not know of any other HW with CBUS. :-/ Fine enough, then please add comments saying that. -- Pengutronix e.K. | Wolfram Sang| Industrial Linux Solutions | http://www.pengutronix.de/ | signature.asc Description: Digital signature
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
On Fri, Sep 14, 2012 at 12:08:06PM +0200, Wolfram Sang wrote:
> On Mon, Sep 03, 2012 at 11:23:22PM +0300, Aaro Koskinen wrote:
> > Add i2c driver to enable access to devices behind CBUS on Nokia Internet
> > Tablets.
> >
> > The patch also adds CBUS I2C configuration for N8x0 which is one of the
> > users of this driver.
> >
> > Cc: linux-...@vger.kernel.org
> > Acked-by: Felipe Balbi
> > Acked-by: Tony Lindgren
> > Signed-off-by: Aaro Koskinen
>
> OK, I found the short paragrahp about CBUS in the I2C spec, so I2C might
> be an appropriate place. Still, before deciding if it should rather be
> in the core directory, I still have a few questions.
Thanks for your feedback. I will fix up the incorrect comments, and do
other improvements (e.g. use devm_* stuff) in the next version.
The questions about delays and bit counts are very valid, but it's
difficult to do anything with them due to lack of documentation and HW on
which to test - I have Nokia tablets to test the driver, and the driver
is very reliable, but I do not know of any other HW with CBUS. :-/
A.
> Also, does anybody know of a generic bit-banging implementation in the
> kernel which could be used here?
>
> Jean: I'd appreciate your general opinion here, too.
>
> > diff --git a/drivers/i2c/busses/i2c-cbus.c b/drivers/i2c/busses/i2c-cbus.c
> > new file mode 100644
> > index 000..bacf2a9
> > --- /dev/null
> > +++ b/drivers/i2c/busses/i2c-cbus.c
> > @@ -0,0 +1,369 @@
> > +/*
> > + * CBUS I2C driver for Nokia Internet Tablets.
> > + *
> > + * Copyright (C) 2004-2010 Nokia Corporation
> > + *
> > + * Based on code written by Juha Yrjölä, David Weinehall, Mikko Ylinen and
> > + * Felipe Balbi. Converted to I2C driver by Aaro Koskinen.
> > + *
> > + * This file is subject to the terms and conditions of the GNU General
> > + * Public License. See the file "COPYING" in the main directory of this
> > + * archive for more details.
> > + *
> > + * 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
> > +#include
> > +#include
> > +#include
> > +#include
> > +#include
> > +#include
> > +#include
> > +#include
> > +#include
> > +#include
> > +#include
> > +#include
> > +
> > +struct cbus_host {
> > + /* host lock */
> > + spinlock_t lock;
> > +
> > + struct device *dev;
> > +
> > + int clk_gpio;
> > + int dat_gpio;
> > + int sel_gpio;
> > +};
> > +
> > +/**
> > + * cbus_send_bit - sends one bit over the bus
> > + * @host: the host we're using
> > + * @bit: one bit of information to send
> > + * @input: whether to set data pin as input after sending
> > + */
> > +static int cbus_send_bit(struct cbus_host *host, unsigned bit,
> > + unsigned input)
> > +{
> > + int ret = 0;
> > +
> > + gpio_set_value(host->dat_gpio, bit ? 1 : 0);
> > + gpio_set_value(host->clk_gpio, 1);
> > +
> > + /* The data bit is read on the rising edge of CLK */
>
> This comment doesn't belong to the if-block, or?
>
> > + if (input)
> > + ret = gpio_direction_input(host->dat_gpio);
>
> No minimum delay for the signal to be on the bus?
>
> > +
> > + gpio_set_value(host->clk_gpio, 0);
> > +
> > + return ret;
> > +}
> > +
> > +/**
> > + * cbus_send_data - sends @len amount of data over the bus
> > + * @host: the host we're using
> > + * @data: the data to send
> > + * @len: size of the transfer
> > + * @input: whether to set data pin as input after sending
> > + */
> > +static int cbus_send_data(struct cbus_host *host, unsigned data, unsigned
> > len,
> > + unsigned input)
> > +{
> > + int ret = 0;
> > + int i;
> > +
> > + for (i = len; i > 0; i--) {
> > + ret = cbus_send_bit(host, data & (1 << (i - 1)),
> > + input && (i == 1));
> > + if (ret < 0)
> > + goto out;
> > + }
> > +
> > +out:
> > + return ret;
> > +}
> > +
> > +/**
> > + * cbus_receive_bit - receives one bit from the bus
> > + * @host: the host we're using
> > + */
> > +static int cbus_receive_bit(struct cbus_host *host)
> > +{
> > + int ret;
> > +
> > + gpio_set_value(host->clk_gpio, 1);
>
> No delays to ensure the signal has stabilized?
>
> > + ret = gpio_get_value(host->dat_gpio);
> > + if (ret < 0)
> > + goto out;
> > + gpio_set_value(host->clk_gpio, 0);
> > +
> > +out:
> > + return ret;
> > +}
> > +
> > +/**
> > + * cbus_receive_word - receives 16-bit word from the bus
> > + * @host: the host we're using
> > + */
> > +static int cbus_receive_word(struct cbus_host *host)
> > +{
> > + int ret = 0;
> > + int i;
> > +
> > + for (i = 16; i > 0; i--) {
> > + int bit = cbus_receive_bit(host);
> > +
> > + if (bit < 0)
> > + goto out;
> >
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
On Fri, Sep 14, 2012 at 12:08:06PM +0200, Wolfram Sang wrote: > On Mon, Sep 03, 2012 at 11:23:22PM +0300, Aaro Koskinen wrote: > > Add i2c driver to enable access to devices behind CBUS on Nokia Internet > > Tablets. > > > > The patch also adds CBUS I2C configuration for N8x0 which is one of the > > users of this driver. > > > > Cc: linux-...@vger.kernel.org > > Acked-by: Felipe Balbi > > Acked-by: Tony Lindgren > > Signed-off-by: Aaro Koskinen > > OK, I found the short paragrahp about CBUS in the I2C spec, so I2C might > be an appropriate place. Still, before deciding if it should rather be > in the core directory, I still have a few questions. > > Also, does anybody know of a generic bit-banging implementation in the > kernel which could be used here? there is i2c-gpio, but it wouldn't help much for cbus, unless we change it quite a lot. The generic i2c_algo_bit_data would have to be changed to learn about a 3 wire bus. I guess the impact is much bigger than just accepting this small, self-contained driver. -- balbi signature.asc Description: Digital signature
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
On Fri, 14 Sep 2012 12:08:06 +0200, Wolfram Sang wrote: > OK, I found the short paragrahp about CBUS in the I2C spec, so I2C might > be an appropriate place. Still, before deciding if it should rather be > in the core directory, I still have a few questions. > > Also, does anybody know of a generic bit-banging implementation in the > kernel which could be used here? > > Jean: I'd appreciate your general opinion here, too. Out of time at the moment :( -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
On Mon, Sep 03, 2012 at 11:23:22PM +0300, Aaro Koskinen wrote:
> Add i2c driver to enable access to devices behind CBUS on Nokia Internet
> Tablets.
>
> The patch also adds CBUS I2C configuration for N8x0 which is one of the
> users of this driver.
>
> Cc: linux-...@vger.kernel.org
> Acked-by: Felipe Balbi
> Acked-by: Tony Lindgren
> Signed-off-by: Aaro Koskinen
OK, I found the short paragrahp about CBUS in the I2C spec, so I2C might
be an appropriate place. Still, before deciding if it should rather be
in the core directory, I still have a few questions.
Also, does anybody know of a generic bit-banging implementation in the
kernel which could be used here?
Jean: I'd appreciate your general opinion here, too.
> diff --git a/drivers/i2c/busses/i2c-cbus.c b/drivers/i2c/busses/i2c-cbus.c
> new file mode 100644
> index 000..bacf2a9
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-cbus.c
> @@ -0,0 +1,369 @@
> +/*
> + * CBUS I2C driver for Nokia Internet Tablets.
> + *
> + * Copyright (C) 2004-2010 Nokia Corporation
> + *
> + * Based on code written by Juha Yrjölä, David Weinehall, Mikko Ylinen and
> + * Felipe Balbi. Converted to I2C driver by Aaro Koskinen.
> + *
> + * This file is subject to the terms and conditions of the GNU General
> + * Public License. See the file "COPYING" in the main directory of this
> + * archive for more details.
> + *
> + * 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
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +
> +struct cbus_host {
> + /* host lock */
> + spinlock_t lock;
> +
> + struct device *dev;
> +
> + int clk_gpio;
> + int dat_gpio;
> + int sel_gpio;
> +};
> +
> +/**
> + * cbus_send_bit - sends one bit over the bus
> + * @host: the host we're using
> + * @bit: one bit of information to send
> + * @input: whether to set data pin as input after sending
> + */
> +static int cbus_send_bit(struct cbus_host *host, unsigned bit,
> + unsigned input)
> +{
> + int ret = 0;
> +
> + gpio_set_value(host->dat_gpio, bit ? 1 : 0);
> + gpio_set_value(host->clk_gpio, 1);
> +
> + /* The data bit is read on the rising edge of CLK */
This comment doesn't belong to the if-block, or?
> + if (input)
> + ret = gpio_direction_input(host->dat_gpio);
No minimum delay for the signal to be on the bus?
> +
> + gpio_set_value(host->clk_gpio, 0);
> +
> + return ret;
> +}
> +
> +/**
> + * cbus_send_data - sends @len amount of data over the bus
> + * @host: the host we're using
> + * @data: the data to send
> + * @len: size of the transfer
> + * @input: whether to set data pin as input after sending
> + */
> +static int cbus_send_data(struct cbus_host *host, unsigned data, unsigned
> len,
> + unsigned input)
> +{
> + int ret = 0;
> + int i;
> +
> + for (i = len; i > 0; i--) {
> + ret = cbus_send_bit(host, data & (1 << (i - 1)),
> + input && (i == 1));
> + if (ret < 0)
> + goto out;
> + }
> +
> +out:
> + return ret;
> +}
> +
> +/**
> + * cbus_receive_bit - receives one bit from the bus
> + * @host: the host we're using
> + */
> +static int cbus_receive_bit(struct cbus_host *host)
> +{
> + int ret;
> +
> + gpio_set_value(host->clk_gpio, 1);
No delays to ensure the signal has stabilized?
> + ret = gpio_get_value(host->dat_gpio);
> + if (ret < 0)
> + goto out;
> + gpio_set_value(host->clk_gpio, 0);
> +
> +out:
> + return ret;
> +}
> +
> +/**
> + * cbus_receive_word - receives 16-bit word from the bus
> + * @host: the host we're using
> + */
> +static int cbus_receive_word(struct cbus_host *host)
> +{
> + int ret = 0;
> + int i;
> +
> + for (i = 16; i > 0; i--) {
> + int bit = cbus_receive_bit(host);
> +
> + if (bit < 0)
> + goto out;
> +
> + if (bit)
> + ret |= 1 << (i - 1);
> + }
> +
> +out:
> + return ret;
> +}
> +
> +/**
> + * cbus_transfer - transfers data over the bus
> + * @host: the host we're using
> + * @rw: read/write flag
> + * @dev: device address
> + * @reg: register address
> + * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0
> + */
> +static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev,
> + unsigned reg, unsigned data)
> +{
> + unsigned long flags;
> + int ret;
> +
> + /* We don't want interrupts disturbing our transfer */
> + spin_lock_irqsave(&host->lock, flags);
> +
> + /* Reset state and start of transfer, SEL stays down
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
On Thu, Sep 13, 2012 at 12:53:09PM +0200, Wolfram Sang wrote: > On Mon, Sep 03, 2012 at 11:23:22PM +0300, Aaro Koskinen wrote: > > Add i2c driver to enable access to devices behind CBUS on Nokia Internet > > Tablets. > > > > The patch also adds CBUS I2C configuration for N8x0 which is one of the > > users of this driver. > > > > Cc: linux-...@vger.kernel.org > > Acked-by: Felipe Balbi > > Acked-by: Tony Lindgren > > Signed-off-by: Aaro Koskinen > > My main question is: what is CBUS? It doesn't look like an I2C/SMBUS > host controller, but some bit-banging protocol? As such, it shouldn't go > to i2c/busses/. And the protocol doesn't look much like I2C, neither. > There is no ACK/NACK/START/STOP, so I wonder if it should be in i2c > after all... It's some legacy 3-wire bus protocol. Not much info is available, there's some references to CBUS in i2c spec, so I thought it wouldn't be a completly wrong place for it... A. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
On Mon, Sep 03, 2012 at 11:23:22PM +0300, Aaro Koskinen wrote: > Add i2c driver to enable access to devices behind CBUS on Nokia Internet > Tablets. > > The patch also adds CBUS I2C configuration for N8x0 which is one of the > users of this driver. > > Cc: linux-...@vger.kernel.org > Acked-by: Felipe Balbi > Acked-by: Tony Lindgren > Signed-off-by: Aaro Koskinen My main question is: what is CBUS? It doesn't look like an I2C/SMBUS host controller, but some bit-banging protocol? As such, it shouldn't go to i2c/busses/. And the protocol doesn't look much like I2C, neither. There is no ACK/NACK/START/STOP, so I wonder if it should be in i2c after all... Jean, maybe you want to have a glimpse on this as well? Regards, Wolfram -- Pengutronix e.K. | Wolfram Sang| Industrial Linux Solutions | http://www.pengutronix.de/ | signature.asc Description: Digital signature
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
Hi, On Tue, Sep 04, 2012 at 12:31:42PM +0300, Aaro Koskinen wrote: > On Tue, Sep 04, 2012 at 12:05:07PM +0300, Felipe Balbi wrote: > > > + * CBUS I2C driver for Nokia Internet Tablets. > > [...] > > > this version misses the entire IRQ handling we already had on linux-omap > > tree, so it's quite a regression. > > There's no interrupts used in plain CBUS protocol/communication I think? > > But Retu MFD supports the GPIO IRQ. I added the code for this set. And > the power button driver (patch 4/4) is using this functionality: > > # cat /proc/interrupts > [...] > 204: 29 GPIO retu-mfd > 224: 29 RETU retu-pwrbutton oops, indeed. My bad. I looked at the wrong patch. Nevermind, this series looks good to me. FWIW: Acked-by: Felipe Balbi (for entire series) -- balbi signature.asc Description: Digital signature
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
On Tue, Sep 04, 2012 at 12:05:07PM +0300, Felipe Balbi wrote: > > + * CBUS I2C driver for Nokia Internet Tablets. [...] > this version misses the entire IRQ handling we already had on linux-omap > tree, so it's quite a regression. There's no interrupts used in plain CBUS protocol/communication I think? But Retu MFD supports the GPIO IRQ. I added the code for this set. And the power button driver (patch 4/4) is using this functionality: # cat /proc/interrupts [...] 204: 29 GPIO retu-mfd 224: 29 RETU retu-pwrbutton A. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 1/4] i2c: introduce i2c-cbus driver
Hi,
On Mon, Sep 03, 2012 at 11:23:22PM +0300, Aaro Koskinen wrote:
> diff --git a/drivers/i2c/busses/i2c-cbus.c b/drivers/i2c/busses/i2c-cbus.c
> new file mode 100644
> index 000..bacf2a9
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-cbus.c
> @@ -0,0 +1,369 @@
> +/*
> + * CBUS I2C driver for Nokia Internet Tablets.
> + *
> + * Copyright (C) 2004-2010 Nokia Corporation
> + *
> + * Based on code written by Juha Yrjölä, David Weinehall, Mikko Ylinen and
> + * Felipe Balbi. Converted to I2C driver by Aaro Koskinen.
> + *
> + * This file is subject to the terms and conditions of the GNU General
> + * Public License. See the file "COPYING" in the main directory of this
> + * archive for more details.
> + *
> + * 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
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +
> +struct cbus_host {
> + /* host lock */
> + spinlock_t lock;
> +
> + struct device *dev;
> +
> + int clk_gpio;
> + int dat_gpio;
> + int sel_gpio;
> +};
> +
> +/**
> + * cbus_send_bit - sends one bit over the bus
> + * @host: the host we're using
> + * @bit: one bit of information to send
> + * @input: whether to set data pin as input after sending
> + */
> +static int cbus_send_bit(struct cbus_host *host, unsigned bit,
> + unsigned input)
> +{
> + int ret = 0;
> +
> + gpio_set_value(host->dat_gpio, bit ? 1 : 0);
> + gpio_set_value(host->clk_gpio, 1);
> +
> + /* The data bit is read on the rising edge of CLK */
> + if (input)
> + ret = gpio_direction_input(host->dat_gpio);
> +
> + gpio_set_value(host->clk_gpio, 0);
> +
> + return ret;
> +}
> +
> +/**
> + * cbus_send_data - sends @len amount of data over the bus
> + * @host: the host we're using
> + * @data: the data to send
> + * @len: size of the transfer
> + * @input: whether to set data pin as input after sending
> + */
> +static int cbus_send_data(struct cbus_host *host, unsigned data, unsigned
> len,
> + unsigned input)
> +{
> + int ret = 0;
> + int i;
> +
> + for (i = len; i > 0; i--) {
> + ret = cbus_send_bit(host, data & (1 << (i - 1)),
> + input && (i == 1));
> + if (ret < 0)
> + goto out;
> + }
> +
> +out:
> + return ret;
> +}
> +
> +/**
> + * cbus_receive_bit - receives one bit from the bus
> + * @host: the host we're using
> + */
> +static int cbus_receive_bit(struct cbus_host *host)
> +{
> + int ret;
> +
> + gpio_set_value(host->clk_gpio, 1);
> + ret = gpio_get_value(host->dat_gpio);
> + if (ret < 0)
> + goto out;
> + gpio_set_value(host->clk_gpio, 0);
> +
> +out:
> + return ret;
> +}
> +
> +/**
> + * cbus_receive_word - receives 16-bit word from the bus
> + * @host: the host we're using
> + */
> +static int cbus_receive_word(struct cbus_host *host)
> +{
> + int ret = 0;
> + int i;
> +
> + for (i = 16; i > 0; i--) {
> + int bit = cbus_receive_bit(host);
> +
> + if (bit < 0)
> + goto out;
> +
> + if (bit)
> + ret |= 1 << (i - 1);
> + }
> +
> +out:
> + return ret;
> +}
> +
> +/**
> + * cbus_transfer - transfers data over the bus
> + * @host: the host we're using
> + * @rw: read/write flag
> + * @dev: device address
> + * @reg: register address
> + * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0
> + */
> +static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev,
> + unsigned reg, unsigned data)
> +{
> + unsigned long flags;
> + int ret;
> +
> + /* We don't want interrupts disturbing our transfer */
> + spin_lock_irqsave(&host->lock, flags);
> +
> + /* Reset state and start of transfer, SEL stays down during transfer */
> + gpio_set_value(host->sel_gpio, 0);
> +
> + /* Set the DAT pin to output */
> + gpio_direction_output(host->dat_gpio, 1);
> +
> + /* Send the device address */
> + ret = cbus_send_data(host, dev, 3, 0);
> + if (ret < 0) {
> + dev_dbg(host->dev, "failed sending device addr\n");
> + goto out;
> + }
> +
> + /* Send the rw flag */
> + ret = cbus_send_bit(host, rw == I2C_SMBUS_READ, 0);
> + if (ret < 0) {
> + dev_dbg(host->dev, "failed sending read/write flag\n");
> + goto out;
> + }
> +
> + /* Send the device address */
> + ret = cbus_send_data(host, reg, 5, rw == I2C_SMBUS_READ);
> + if (ret < 0) {
> + dev_dbg(host->dev, "failed sending register addr\n");
> +
