[U-Boot] [PATCH] Exynos5: i2c: Fix read NACK handling and remove some redundancy

[Hung-ying Tyan]

On which branch is this patch based? It looks quite off from ToT.


On Mon, Mar 25, 2013 at 7:46 PM, Akshay Saraswat <akshay.s at samsung.com>wrote:

> From: Gabe Black <gabeblack at google.com>
>
> The exynos s3c24x0 i2c driver wouldn't do the right thing when a NACK was
> received on a read because it didn't attempt a read before waiting for the
> read to finish. Putting a call to ReadWriteByte in the NACK path fixed a
> problem where getting a NACK reading from a device would jam up the bus and
> prevent future accesses like probing from working.
>
> Because other than the ReadWriteByte call the NACK and normal paths were
> almost the same thing, and to avoid future instances of the NACK path not
> working because it's not exercised normally, this change also consolidates
> those two paths.
>
> Signed-off-by: Gabe Black <gabeblack at google.com>
> Signed-off-by: Akshay Saraswat <akshay.s at samsung.com>
> ---
>  drivers/i2c/s3c24x0_i2c.c | 53
> ++++++++++++++++-------------------------------
>  1 file changed, 18 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/i2c/s3c24x0_i2c.c b/drivers/i2c/s3c24x0_i2c.c
> index d2b4eb0..91298a7 100644
> --- a/drivers/i2c/s3c24x0_i2c.c
> +++ b/drivers/i2c/s3c24x0_i2c.c
> @@ -366,21 +366,25 @@ static int i2c_transfer(struct s3c24x0_i2c *i2c,
>                 break;
>
>         case I2C_READ:
> -               if (result == I2C_OK) {
> -                       writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
> -                       writel(chip, &i2c->iicds);
> -                       /* send START */
> -                       writel(readl(&i2c->iicstat) | I2C_START_STOP,
> -                              &i2c->iicstat);
> -                       ReadWriteByte(i2c);
> -                       result = WaitForXfer(i2c);
> +       {
> +               int was_ok = (result == I2C_OK);
> +
> +               writel(chip, &i2c->iicds);
> +               /* resend START */
> +               writel(I2C_MODE_MR | I2C_TXRX_ENA |
> +                                       I2C_START_STOP, &i2c->iicstat);
> +               ReadWriteByte(i2c);
> +               result = WaitForXfer(i2c);
> +
> +               if (was_ok || IsACK(i2c)) {
>                         i = 0;
>                         while ((i < data_len) && (result == I2C_OK)) {
>                                 /* disable ACK for final READ */
> -                               if (i == data_len - 1)
> -                                       writel(readl(&i2c->iiccon)
> -                                                       & ~I2CCON_ACKGEN,
> -                                                       &i2c->iiccon);
> +                               if (i == data_len - 1) {
> +                                       writel(readl(&i2c->iiccon) &
> +                                             ~I2CCON_ACKGEN,
> +                                             &i2c->iiccon);
> +                               }
>                                 ReadWriteByte(i2c);
>                                 result = WaitForXfer(i2c);
>                                 data[i] = readl(&i2c->iicds);
> @@ -388,35 +392,14 @@ static int i2c_transfer(struct s3c24x0_i2c *i2c,
>                         }
>
>                 } else {
> -                       writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
> -                       writel(chip, &i2c->iicds);
> -                       /* send START */
> -                       writel(readl(&i2c->iicstat) | I2C_START_STOP,
> -                              &i2c->iicstat);
> -                       result = WaitForXfer(i2c);
> -
> -                       if (IsACK(i2c)) {
> -                               i = 0;
> -                               while ((i < data_len) && (result ==
> I2C_OK)) {
> -                                       /* disable ACK for final READ */
> -                                       if (i == data_len - 1)
> -                                               writel(readl(&i2c->iiccon)
> &
> -                                                       ~I2CCON_ACKGEN,
> -                                                       &i2c->iiccon);
> -                                       ReadWriteByte(i2c);
> -                                       result = WaitForXfer(i2c);
> -                                       data[i] = readl(&i2c->iicds);
> -                                       i++;
> -                               }
> -                       } else {
> -                               result = I2C_NACK;
> -                       }
> +                       result = I2C_NACK;
>                 }
>
>                 /* send STOP */
>                 writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
>                 ReadWriteByte(i2c);
>                 break;
> +       }
>
>         default:
>                 debug("i2c_transfer: bad call\n");
> --
> 1.8.0
>
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