[i2c] [PATCH] Add polling transfer for i2c-pxa

eric miao eric.y.miao at gmail.com
Tue Nov 13 10:01:01 CET 2007


Hi Mike,

Here are the questions:

1. it looks like the implementation doesn't support slave mode in polling mode.
2. When switch to next segment message, a repeated restart would be better
send to hold the I2C bus. That seems to be what the original interrupt driven
code is doing...??

On Nov 6, 2007 8:17 PM, Mike Rapoport <mike at compulab.co.il> wrote:
> The below patch adds polling I2C transfer implementation for PXA I2C.
> It coexists with interrupt-based transfers and can be used within
> interrupts-off contexts.
>
> --
> Sincerely yours,
> Mike.
>
> Signed-off-by: Mike Rapoport <mike at compulab.co.il>
>
> diff --git a/drivers/i2c/busses/i2c-pxa.c b/drivers/i2c/busses/i2c-pxa.c
> index 6426a61..0aa6c82 100644
> --- a/drivers/i2c/busses/i2c-pxa.c
> +++ b/drivers/i2c/busses/i2c-pxa.c
> @@ -554,6 +554,169 @@ static inline void i2c_pxa_stop_message(struct pxa_i2c *i2c)
>         writel(icr, _ICR(i2c));
>  }
>
> +static int i2c_pxa_isr_set_cleared(struct pxa_i2c *i2c,
> +                                  unsigned long set_mask,
> +                                  unsigned long cleared_mask)
> +{
> +       int timeout = 10000;
> +
> +       while (((readl(_ISR(i2c)) & set_mask) != set_mask) ||
> +              ((readl(_ISR(i2c)) & cleared_mask) != 0)) {
> +               udelay(10);
> +               if (timeout-- < 0)
> +                       return -ETIMEDOUT;
> +       }
> +
> +       return 0;
> +}
> +
> +static int i2c_pxa_pio_set_master(struct pxa_i2c *i2c)
> +{
> +       /* make timeout the same as for interrupt based functions */
> +       long timeout = 2 * DEF_TIMEOUT;
> +
> +       /*
> +        * Wait for the bus to become free.
> +        */
> +       while (timeout-- && readl(_ISR(i2c)) & (ISR_IBB | ISR_UB)) {
> +               udelay(1000);
> +               show_state(i2c);
> +       }
> +
> +       if (timeout <= 0) {
> +               show_state(i2c);
> +               dev_err(&i2c->adap.dev,
> +                       "i2c_pxa: timeout waiting for bus free\n");
> +               return I2C_RETRY;
> +       }
> +
> +       /*
> +        * Set master mode.
> +        */
> +       writel(readl(_ICR(i2c)) | ICR_SCLE, _ICR(i2c));
> +
> +       return 0;
> +}
> +
> +static int i2c_pxa_do_pio_xfer(struct pxa_i2c *i2c,
> +                              struct i2c_msg *msg, int num)
> +{
> +       int ret = 0;
> +       u32 icr;
> +
> +       ret = i2c_pxa_pio_set_master(i2c);
> +       if (ret)
> +               goto out;
> +
> +       i2c->msg = msg;
> +       i2c->msg_num = num;
> +       i2c->msg_idx = 0;
> +       i2c->msg_ptr = 0;
> +       i2c->irqlogidx = 0;
> +
> +       for (i2c->msg_idx = 0;
> +            i2c->msg_idx < num;
> +            i2c->msg_idx++, i2c->msg++) {
> +               if (i2c->msg_idx == 0 || !(i2c->msg->flags & I2C_M_NOSTART))
> +                       i2c_pxa_start_message(i2c);
> +
> +               ret = i2c_pxa_isr_set_cleared(i2c, ISR_ITE, 0);
> +               if (ret)
> +                       goto out;
> +
> +               /* update the irq log same way is interrupt based transfers */
> +               if (i2c->irqlogidx < ARRAY_SIZE(i2c->isrlog))
> +                       i2c->isrlog[i2c->irqlogidx++] = readl(_ISR(i2c));
> +
> +               writel(ISR_ITE, _ISR(i2c));
> +
> +               for (i2c->msg_ptr = 0;
> +                    i2c->msg_ptr < i2c->msg->len;
> +                    i2c->msg_ptr++) {
> +                       icr = readl(_ICR(i2c)) &
> +                               ~(ICR_START|ICR_STOP|ICR_ACKNAK|ICR_TB);
> +                       icr |= ICR_TB;
> +
> +                       if (i2c->msg->flags & I2C_M_RD) {
> +                               if (i2c->msg_ptr == i2c->msg->len - 1)
> +                                       icr |= ICR_STOP | ICR_ACKNAK;
> +
> +                               i2c->icrlog[i2c->irqlogidx-1] = icr;
> +                               writel(icr, _ICR(i2c));
> +
> +                               ret = i2c_pxa_isr_set_cleared(i2c, ISR_IRF, 0);
> +                               if (ret)
> +                                       goto out;
> +
> +                               writel(ISR_IRF, _ISR(i2c));
> +
> +                               i2c->msg->buf[i2c->msg_ptr] = readl(_IDBR(i2c));
> +                       } else {
> +                               writel(i2c->msg->buf[i2c->msg_ptr], _IDBR(i2c));
> +                               /* If this is the last byte of the
> +                                  last message, send a STOP. */
> +                               if (i2c->msg_ptr == i2c->msg->len - 1 &&
> +                                   i2c->msg_idx == num - 1)
> +                                       icr |= ICR_STOP;
> +
> +                               i2c->icrlog[i2c->irqlogidx-1] = icr;
> +                               writel(icr, _ICR(i2c));
> +
> +                               ret = i2c_pxa_isr_set_cleared(i2c, ISR_ITE, 0);
> +                               if (ret)
> +                                       goto out;
> +
> +                               writel(ISR_ITE, _ISR(i2c));
> +                       }
> +               }
> +       }
> +
> +       i2c_pxa_stop_message(i2c);
> +
> +       /*
> +        * We place the return code in i2c->msg_idx.
> +        */
> +       ret = i2c->msg_idx;
> +       i2c->msg_ptr = 0;
> +       i2c->msg = NULL;
> +       i2c->msg_num = 0;
> +
> +out:
> +       if (ret < 0)
> +               i2c_pxa_scream_blue_murder(i2c, "timeout");
> +
> +       return ret;
> +}
> +
> +static int i2c_pxa_pio_xfer(struct i2c_adapter *adap,
> +                           struct i2c_msg msgs[], int num)
> +{
> +       struct pxa_i2c *i2c = adap->algo_data;
> +       int ret, i;
> +
> +       /* If the I2C controller is disabled we need to reset it
> +         (probably due to a suspend/resume destroying state). We do
> +         this here as we can then avoid worrying about resuming the
> +         controller before its users. */
> +       if (!(readl(_ICR(i2c)) & ICR_IUE))
> +               i2c_pxa_reset(i2c);
> +
> +       for (i = adap->retries; i >= 0; i--) {
> +               ret = i2c_pxa_do_pio_xfer(i2c, msgs, num);
> +               if (ret != I2C_RETRY)
> +                       goto out;
> +
> +               if (i2c_debug)
> +                       dev_dbg(&adap->dev, "Retrying transmission\n");
> +               udelay(100);
> +       }
> +       i2c_pxa_scream_blue_murder(i2c, "exhausted retries");
> +       ret = -EREMOTEIO;
> + out:
> +       i2c_pxa_set_slave(i2c, ret);
> +       return ret;
> +}
> +
>  /*
>   * We are protected by the adapter bus mutex.
>   */
> @@ -837,6 +1000,7 @@ static u32 i2c_pxa_functionality(struct i2c_adapter *adap)
>
>  static const struct i2c_algorithm i2c_pxa_algorithm = {
>         .master_xfer    = i2c_pxa_xfer,
> +       .pio_xfer       = i2c_pxa_pio_xfer,
>         .functionality  = i2c_pxa_functionality,
>  };
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 1a4e8dc..37e3cd9 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -33,6 +33,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/mutex.h>
>  #include <linux/completion.h>
> +#include <linux/delay.h>
>  #include <asm/uaccess.h>
>
>  #include "i2c-core.h"
> @@ -870,7 +871,24 @@ int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
>  {
>         int ret;
>
> -       if (adap->algo->master_xfer) {
> +       if (in_atomic() || irqs_disabled()) {
> +               int retries = 1;
> +               if (adap->algo->pio_xfer == NULL) {
> +                       pr_debug("%s: algo has no poll xfer", __FUNCTION__);
> +                       return -EINVAL;
> +               }
> +               ret = mutex_trylock(&adap->bus_lock);
> +               if (ret) { /* We get bus_lock, no ongoing I2C activity */
> +                       ret = adap->algo->pio_xfer(adap, msgs, num);
> +                       mutex_unlock(&adap->bus_lock);
> +                       return ret;
> +               } else {
> +                       /* I2C activity is ongoing. */
> +                       /* FIXME: may be we should take the lock and
> +                          abandon ongoing transfer */
> +                       return -EBUSY;
> +               }
> +       } else if (adap->algo->master_xfer) {
>  #ifdef DEBUG
>                 for (ret = 0; ret < num; ret++) {
>                         dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, "
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 8033e6b..7e24466 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -290,6 +290,10 @@ struct i2c_algorithm {
>                            unsigned short flags, char read_write,
>                            u8 command, int size, union i2c_smbus_data * data);
>
> +       /* PIO xfer can be used in no-interrupts context */
> +       int (*pio_xfer)(struct i2c_adapter *adap, struct i2c_msg *msgs,
> +                       int num);
> +
>         /* To determine what the adapter supports */
>         u32 (*functionality) (struct i2c_adapter *);
>  };
>
>
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> i2c at lm-sensors.org
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>



-- 
Cheers
- eric



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