On Tue, Jan 12, 2010 at 04:47:16PM +0530, Philby John wrote: > >From 2565eeda807e49376298ec895a0d9a91a7668417 Mon Sep 17 00:00:00 2001 > From: Philby John <[email protected]> > Date: Mon, 11 Jan 2010 22:39:44 +0530 > Subject: [PATCH 2/2] Davinci i2c bus recovery procedure to clear the bus > > Come out of i2c time out condition by following the > bus recovery procedure outlined in the i2c protocol v3 spec. > The kernel must be robust enough to gracefully recover > from i2c bus failure without having to reset the machine. > This is done by first NACKing the slave, pulsing the SCL > line 9 times and then sending the stop command. > > This patch has been tested on a DM6446 and DM355
Still not sure whether this can be included as a bug-fix or whether it comes under the new feature category. Also, since it has to get new data from the platform whose tree it should really go into. > Signed-off-by: Philby John <[email protected]> > Signed-off-by: Srinivasan, Nageswari <[email protected]> > --- > drivers/i2c/busses/i2c-davinci.c | 57 +++++++++++++++++++++++++++++++++++-- > 1 files changed, 53 insertions(+), 4 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-davinci.c > b/drivers/i2c/busses/i2c-davinci.c > index 35f9daa..5459065 100644 > --- a/drivers/i2c/busses/i2c-davinci.c > +++ b/drivers/i2c/busses/i2c-davinci.c > @@ -36,6 +36,7 @@ > #include <linux/platform_device.h> > #include <linux/io.h> > #include <linux/cpufreq.h> > +#include <linux/gpio.h> > > #include <mach/hardware.h> > #include <mach/i2c.h> > @@ -43,6 +44,7 @@ > /* ----- global defines ----------------------------------------------- */ > > #define DAVINCI_I2C_TIMEOUT (1*HZ) > +#define DAVINCI_I2C_MAX_TRIES 2 > #define I2C_DAVINCI_INTR_ALL (DAVINCI_I2C_IMR_AAS | \ > DAVINCI_I2C_IMR_SCD | \ > DAVINCI_I2C_IMR_ARDY | \ > @@ -130,6 +132,44 @@ static inline u16 davinci_i2c_read_reg(struct > davinci_i2c_dev *i2c_dev, int reg) > return __raw_readw(i2c_dev->base + reg); > } > > +/* Generate a pulse on the i2c clock pin. */ > +static void generic_i2c_clock_pulse(unsigned int scl_pin) > +{ > + u16 i; > + > + if (scl_pin) { > + /* Send high and low on the SCL line */ > + for (i = 0; i < 9; i++) { > + gpio_set_value(scl_pin, 0); > + udelay(20); > + gpio_set_value(scl_pin, 1); > + udelay(20); > + } > + } > +} > + > +/* This routine does i2c bus recovery as specified in the > + * i2c protocol Rev. 03 section 3.16 titled "Bus clear" > + */ > +static void i2c_recover_bus(struct davinci_i2c_dev *dev) > +{ > + u32 flag = 0; > + struct davinci_i2c_platform_data *pdata = dev->dev->platform_data; > + > + dev_err(dev->dev, "initiating i2c bus recovery\n"); > + /* Send NACK to the slave */ > + flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG); > + flag |= DAVINCI_I2C_MDR_NACK; > + /* write the data into mode register */ > + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag); > + if (pdata) > + generic_i2c_clock_pulse(pdata->scl_pin); > + /* Send STOP */ > + flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG); > + flag |= DAVINCI_I2C_MDR_STP; > + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag); > +} > + > static inline void davinci_i2c_reset_ctrl(struct davinci_i2c_dev *i2c_dev, > int val) > { > @@ -235,14 +275,22 @@ static int i2c_davinci_wait_bus_not_busy(struct > davinci_i2c_dev *dev, > char allow_sleep) > { > unsigned long timeout; > + static u16 to_cnt; > > timeout = jiffies + dev->adapter.timeout; > while (davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG) > & DAVINCI_I2C_STR_BB) { > - if (time_after(jiffies, timeout)) { > - dev_warn(dev->dev, > - "timeout waiting for bus ready\n"); > - return -ETIMEDOUT; > + if (to_cnt <= DAVINCI_I2C_MAX_TRIES) { > + if (time_after(jiffies, timeout)) { > + dev_warn(dev->dev, > + "timeout waiting for bus ready\n"); > + to_cnt++; > + return -ETIMEDOUT; > + } else { > + to_cnt = 0; > + i2c_recover_bus(dev); > + i2c_davinci_init(dev); > + } > } > if (allow_sleep) > schedule_timeout(1); > @@ -324,6 +372,7 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct > i2c_msg *msg, int stop) > dev->adapter.timeout); > if (r == 0) { > dev_err(dev->dev, "controller timed out\n"); > + i2c_recover_bus(dev); > i2c_davinci_init(dev); > dev->buf_len = 0; > return -ETIMEDOUT; > -- > 1.6.3.3.MVISTA > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-i2c" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Ben ([email protected], http://www.fluff.org/) 'a smiley only costs 4 bytes' -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
