Hello Troy,
On Wed, 2009-07-15 at 10:15 -0700, Troy Kisky wrote:
> Philby John wrote:
> >>From dbe7e824d576636bb15b82a20fd2557fddc9a8f7 Mon Sep 17 00:00:00 2001
> > From: Philby John <pjohn@xxxxxxxxxxxxx>
> > 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 <pjohn@xxxxxxxxxxxxx>
> > ---
>
> 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
Yes, I agree. I wait for a maximum of 2 tries when a timeout occurs
before initiating bus recovery.
Regards,
Philby
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