Philby John wrote:
>>From dbe7e824d576636bb15b82a20fd2557fddc9a8f7 Mon Sep 17 00:00:00 2001
> From: Philby John <pj...@in.mvista.com>
> Date: Tue, 14 Jul 2009 21:46:47 +0530
> Subject: [PATCH] Reset i2c bus to come out of time out conditions
>
> Get out of i2c time out condition by resetting
> the i2c bus. 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
> and then resetting the i2c bus after a certain timeout.
>
> Signed-off-by: Philby John <pj...@in.mvista.com>
> ---
I personally like the idea behind this patch. But I have
heard others argue against it. But it is not related to the
^C issue others have mentioned. That should not happen in
the GIT kernel.
> drivers/i2c/busses/i2c-davinci.c | 98 +++++++++++++++++++++++++++++++++++--
> 1 files changed, 92 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-davinci.c
> b/drivers/i2c/busses/i2c-davinci.c
> index 17f2ee7..4ed1a4c 100755
> --- a/drivers/i2c/busses/i2c-davinci.c
> +++ b/drivers/i2c/busses/i2c-davinci.c
> @@ -35,14 +35,18 @@
> #include <linux/interrupt.h>
> #include <linux/platform_device.h>
> #include <linux/io.h>
> +#include <linux/gpio.h>
>
> #include <mach/hardware.h>
>
> #include <mach/i2c.h>
> +#include <mach/mux.h>
> +#include <mach/cputype.h>
>
> /* ----- 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 | \
> @@ -135,6 +139,50 @@ static inline u16 davinci_i2c_read_reg(struct
> davinci_i2c_dev *i2c_dev, int reg)
> }
>
> /*
> + * Configure the i2c data pin as a GPIO input and the i2c clock pin as a
> + * high GPIO output.
> + */
> +static void disable_i2c_pins(void)
> +{
> + unsigned long flags;
> +
> + local_irq_save(flags);
> + if (cpu_is_davinci_dm355()) {
> + gpio_direction_input(15);
> + gpio_direction_output(14, 0);
> + gpio_set_value(14, 1);
> + davinci_cfg_reg(DM355_I2C_SDA);
> + davinci_cfg_reg(DM355_I2C_SCL);
> + }
> + local_irq_restore(flags);
> +}
> +
> +/* Connect the i2c pins to the i2c controller. */
> +static void enable_i2c_pins(void)
> +{
> + unsigned long flags;
> +
> + local_irq_save(flags);
> + if (cpu_is_davinci_dm355()) {
> + davinci_cfg_reg(DM355_I2C_SDA);
> + davinci_cfg_reg(DM355_I2C_SCL);
> + }
> + local_irq_restore(flags);
> +}
> +
> +
> +/* Generate a pulse on the i2c clock pin. */
> +static void pulse_i2c_clock(void)
> +{
> + if (cpu_is_davinci_dm355()) {
> + gpio_set_value(14, 0);
> + udelay(20);
> + gpio_set_value(14, 1);
> + udelay(20);
> + }
> +}
> +
> +/*
> * This functions configures I2C and brings I2C out of reset.
> * This function is called during I2C init function. This function
> * also gets called if I2C encounters any errors.
> @@ -221,14 +269,36 @@ static int i2c_davinci_wait_bus_not_busy(struct
> davinci_i2c_dev *dev,
> char allow_sleep)
> {
> unsigned long timeout;
> + u16 i;
> + static u16 to_cnt = 0;
> + u32 flag = 0;
>
> 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;
> + & DAVINCI_I2C_STR_BB) {
> +
> + 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 if (cpu_is_davinci_dm644x() || cpu_is_davinci_dm355()) {
I would not initiate recovery until a timeout occurs.
This can be a multi master bus, so a busy condition
may be valid. Then, after multiple timeouts and recovery attempts,
return -ETIMEDOUT
> + to_cnt = 0;
> + dev_err(dev->dev, "initiating i2c bus recovery\n");
> + /* Send the NACK to the slave */
> + flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_IMR_REG);
> + flag |= DAVINCI_I2C_MDR_NACK;
> + /* write the data into mode register */
> + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
> + /* Disable i2c */
> + disable_i2c_pins();
> + for (i = 0; i < 10; i++)
> + pulse_i2c_clock();
> + /* Re-enable i2c */
> + enable_i2c_pins();
> + i2c_davinci_init(dev);
> }
> if (allow_sleep)
> schedule_timeout(1);
> @@ -309,7 +379,23 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct
> i2c_msg *msg, int stop)
> r = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
> dev->adapter.timeout);
> if (r == 0) {
> - dev_err(dev->dev, "controller timed out\n");
> + u16 i;
> + u32 flag = 0;
> + if (cpu_is_davinci_dm644x() || cpu_is_davinci_dm355()) {
> + dev_err(dev->dev, "initiating i2c bus recovery\n");
> + /* Send the NACK to the slave */
> + flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_IMR_REG);
> + flag |= DAVINCI_I2C_MDR_NACK;
> + /* write the data into mode register */
> + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
> + /* Disable i2c */
> + disable_i2c_pins();
> + /* Send high and low on the SCL line */
> + for (i = 0; i < 10; i++)
> + pulse_i2c_clock();
> + /* Re-enable i2c */
> + enable_i2c_pins();
> + }
> i2c_davinci_init(dev);
> dev->buf_len = 0;
> return -ETIMEDOUT;
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